,field ,book of ,common ,rocks and ,minerals ,for identifying the ,rocks and ,minerals of the ,united ,states and interpreting their ,origins and ,meanings ,by ,frederic ,brewster ,loomis ,late ,professor of ,mineralogy and ,geology in ,amherst ,college ,with #dg ,colored ,specimens and over #ajj other ,illustrations from ,photographs by ,w4 ,e4 ,corbin and drawings by the ,author ,g4 ,p4 ,putnam's ,sons ,new ,york and ,london ,,field ,,book ,,of ,,common ,,rocks ,,and ,,minerals ,copyright1 #aibc1 #aidh by ,frederick ,brewster ,loomis ,twenty-sixth ,impression ,revised #aidh ,all rights reserved4 ,this book1 or parts thereof1 must not be reproduced in any form without permission4 ,made in the ,united ,states of ,america ,dedicated ,,to ,,my ,,mother ,,who ,,encouraged ,,me ,,while ,a ,,boy ,,to ,,gather ,,minerals1 ,,rocks ,,and ,,fossils4 ,,preface ,everyone1 who is alert as he wanders about this world1 wants to know what he is seeing and what it is all about4 ,here and there with the aid of capable guides a few have been introduced into the sphere of that wide and fascinating knowledge of ,nature which has been so rapidly accumulated during this and the latter part of the last century4 ,it is a full treasure house constantly being enriched1 but unfortunately the few who have been initiated have soon acquired a technical language and habit1 so that their knowledge and new acquisitions are communicated to but few4 ,the public at large1 not having the language nor an interpreter at hand1 has come almost at once to a barrier which few have the time or patience to surmount4 ,latterly it has become clear that the largest progress cannot be made if the knowledge of any branch of ,science is confined to a few only4 ,the most rapid advances have been made where many men are interested and enthusiastic4 ,in no science should there be a difficult barrier between the amateur and the professional student4 ,all ,nature is equally open for everyone to study1 and there should never be created obstacles as by the use of terminology not easily acquired by anyone4 ,of late these barriers have been in part broken down and competent students have written guides which anyone can follow1 and soon begin to know the plants1 trees1 birds1 insects1 etc4 ,so far no one has attempted to make the study of minerals and rocks so direct and simple that everyone can get a start4 ,most books on minerals1 and practically all those on rocks are written for school courses1 and to say the least chill any enthusiasm which is naturally aroused by the finding of interesting looking rocks or minerals4 ,the purpose of this book is first of all to provide a means of identifying minerals and rocks by such methods as are practical without elaborate equipment or previous training3 and second to suggest the conditions under which the various minerals and rocks were formed1 so that1 at the first contact1 one may get a conception of the events which have anteceded the mineral or rock which has been found4 ,for this purpose keys have been worked out for determining the rocks and minerals by such obvious features as color1 hardness1 etc4 ,each mineral or rock is introduced by a summary of its characters1 then the features by which it may be distinguished from any other similar mineral are given1 after which its mode of origin and its meanings are considered4 ,for those interested in the composition of the minerals1 it is given in chemical symbols with each mineral4 ,most classifications of minerals are based on the composition1 all the sulphides1 carbonates1 etc41 being grouped together1 but in this book1 because the popular interest and commercial uses are primarily in the metal present1 the minerals are grouped in each case about the chief metal1 all the minerals of iron being grouped together1 for instance4 ,a few minerals and rocks which are not strictly common have been included such as gems and meteorites2 the gems because they are of intense interest to their owners and are often simply perfect examples of a fairly common mineral2 and such forms as meteorites because it is important that1 if one should run across one1 it should be recognized1 and so not lost to the world4 ,the book is freely illustrated1 those minerals in which color is important for identification being illustrated in colors1 and those which are black1 or in which the color is not a determining factor1 are shown in either photographic or outline figures4 ,in the introductory chapter there are explanations of the terms used in describing minerals1 and of the systems in which they are grouped4 ,a knowledge of the systems may not be a necessity1 but it is a great help in determining minerals1 and is very important in understanding why the individual minerals take the varied forms which are characteristic of them4 ,these systems will be better understood after a few minerals have been gathered and examined4 ,it is hoped the book will help those who have already some knowledge of rocks and minerals1 and especially that it will tempt many to begin an acquaintance with the rocks and minerals which are all about them1 and are the foundation on which our material progress is built4 ,rocks and minerals have some advantages over most objects which are collected in that they neither require special preparation before they can be kept1 nor do they deteriorate with time4 ,the author will appreciate corrections or suggestions as to better presentation of the material in this book4 ,f4 ,b4 ,l4 ,amherst1 ,mass4 ,,contents ,,page ,preface vii ,,chapter ,i4--,an ,introduction #c ,,ii4--,on the ,forms and ,properties of ,minerals #aj ,,iii4--,the ,minerals #be ,,iv4--,the ,rocks #agj ,v4--,miscellaneous ,rocks #bdh ,bibliography #bgj ,index #bgc ,,list ,,of ,,plates 7,,at ,,end ,,of ,,book7 ,,page ,tourmaline crystals1 growing amid feldspar crystals in a cavity in granite1 from ,paris1 ,me4 #bgi ,plate #a4--;,basal forms of the isometric system #caa ,plate #b4--;,basal forms of the tetragonal system4 ,basal forms of the orthorhombic system #cab ,plate #c4--;,basal forms of the monoclinic system4 ,a cross section of the prism with its edges beveled so that a six-sided prism is formed 7pseudo-hexagonal74 ,basal form of the triclinic system4 #cac ,plate #d4--;,basal forms of the hexagonal system #cad ,plate #e4--;,gold in quartz from ,california 7in color7 #bhj ,plate #f4--,native silver in calcite4 ,argentite1 the black masses throughout the white quartz 7in color7 #bha ,plate #g4--,pyrargyrite as it appears after moderate exposure to the light2 streak at left4 ,crystal form of pyrargyrite4 ,prousite as it appears after moderate exposure to the light2 streak at left 7in color7 #bhb ,plate #h4--,native copper from ,michigan4 ,chalcopyrite in tetrahedrons and an occasional octahedron2 streak to the left 7in color7 #bhc ,plate #i4--;,chalcocite crystals with the bluish tarnish4 ,tetrahedrite crystals2 streak to left 7in color7 #bhd ,plate #aj4--,tetrahedrons showing characteristic manner in which tetrahedrite occurs4 ,a cube with the edges beveled and the corners cut in a form characteristic of cuprite #cae ,plate #aa4--;,cuprite1 the red crystals showing characteristic color1 others showing the green tarnish of malachite4 ,malachite 7green7 and azurite 7blue71 the two minerals shown together as they very commonly occur 7in color7 #bhe ,plate #ab4--,limonite4 ,the crystal form in which goethite is found 7in color7 #bhf ,plate #ac4--;,hematite4 ,clinton iron ore1 oolitic4 ,siderite crystals 7in color7 #bhg ,plate #ad4--;,crystal forms of hematite4 ,a typical crystal of magnetite4 ,the rhombohedron typical of siderite #cag ,plate #ae4--,pyrite crystals4 ,marcasite in concretionary form with radiate structure 7in color7 #bhh ,plate #af4--,the pyritohedron4 ,the pyritohedron with certain of its edges beveled by the cube faces1 to show the relationship of these two forms #cah ,plate #ag4--;,galena in crystals4 ,pyromorphite crystals 7,green7 7in color7 #bhi ,plate #ah4--,typical forms for cerrusite4 ,forms in which anglesite occurs #cai ,plate #ai4--,sphalerite1 some the normal yellow and some crystals with the reddish tinge4 7,white is dolomite47 ,zincite1 streak to the left 7in color7 #bij ,plate #bj4--;,a characteristic form in which sphalerite may occur4 ,characteristic form for zincite crystals4 ,typical form of crystal of willemite #cbj ,plate #ba4--,smithsonite in yellow crystals4 ,franklinite in octahedral crystals1 streak to left 7in color7 #bia ,plate #bb4--,moss agates1 showing the dendritic growth of manganitic minerals1 like manganite or pyrolusite4 ,crystal form of manganite #cba ,plate #bc4--;,crystals of green corundum in syenite1 from ,montana4 ,typical crystal forms of corundum #cbb ,plate #bd4--;,arsenopyrite1 showing crystals massed so as to be incompletely developed4 ,realgar as it usually occurs in powdery incrustations 7in color7 #bib ,plate #be4--,large crystals of stibnite2 the light colored face is the one parallel to which cleavage occurs4 ,niccolite is a vein in slate 7in color7 #bic ,plate #bf4--;,cobaltite1 silver color1 with pink tinge4 ,smaltite1 pink is cobalt bloom 7in color7 #bid ,plate #bg4--;,carnotite from ,southwest ,colorado4 ,cinnabar 7in color7 #bie ,plate #bh4--;,cassiterite1 twinned crystals4 ,the crystal form in which both cassiterite and rutile occur when in simple crystals4 ,multiple twinning characteristic of rutile #cbc ,plate #bi4--;,crystal of spinel4 ,crystal forms in which dolomite occurs #cbd ,plate #cj4--,two intergrowing or twinned quartz crystals4 ,diagram of the typical quartz crystal4 ,a quartz crystal on which the left hand rhombohedron is represented by small faces1 while the right hand rhombohedron has large faces #caf ,plate #ca4--;,amethyst1 not however deep enough colored for gems4 ,jasper1 with botryoidal surface 7in color7 #bif ,plate #cb4--;,banded agate from ,brazil 7in color7 #big ,plate #cc4--;,common opal from ,arizona4 ,siliceous sinter or geyserite from ,yellowstone ,park 7in color7 #bih ,plate #cd4--,orthoclase1 a cleavage piece4 ,crystal forms of orthoclase4 ,diagram of a multiple twin of a plagioclase feldspar #cbe ,plate #ce4--;,a group of microcline crystals from ,pike's ,peak1 ,colo4 ,labradorite1 showing multiple twinning 7the striation7 and the iridescent play of colors 7in color7 #bii ,plate #cf4--;,crystal form of a pyroxene4 ,cross sections of a pyroxene crystal showing the lines of intersection of two cleavage planes4 ,cross sections of pyroxenes1 showing typical forms taken by crystals4 ,augite crystals1 in crystalline limestone 7in color7 #cjj ,plate #cg4--;,diagrams of amphibole crystals4 ,tremolite in silky fibrous crystals1 asbestos4 ,hornblende crystals in quartzite #cbf ,plate #ch4--,the dodecahedron and the #bd-sided figure characteristic of garnets4 ,the garnet1 grossularite4 ,the garnet1 alamandite 7in color7 #cja ,plate #ci4--;,beryl of gem quality4 ,zircon in syenite 7in color7 #cjb ,plate #dj4--;,cyanite crystals in schist4 ,a crystal of mica1 showing basal cleavage 7in color7 #cjc ,plate #da4--;,crystal form typical of topaz4 ,a topaz crystal from ,brazil4 ,crystal form typical of staurolite when simple4 ,a typical twin of staurolite 7in color7 #cjd ,plate #db4--;,epidote crystals4 ,typical forms of epidote crystals4 ,typical forms of tourmaline #cbg ,plate #dc4--,serpentine4 ,chlorite 7in color7 #cje ,plate #dd4--,the typical form of analcite4 ,a typical natrolite crystal4 ,the typical crystal form of stilbite4 ,a sheaf-like bundle of fibrous crystals1 typical of stilbite #cbi ,plate #de4--;,a group of calcite crystals4 ,typical forms of calcite #ccj ,plate #df4--,typical forms of aragonite4 ,typical form of the anhydrite crystal #cca ,plate #dg4--;,a piece of gypsum looking on the surface of the perfect cleavage1 and showing the two other cleavages as lines1 intersecting at #ff4 ,twinning is also shown4 ,a simple crystal of gypsum4 ,twin crystals of gypsum4 #ccb ,plate #dh4--;,a group of barite crystals4 ,outline of the typical tabular barite crystal4 ,the six-sided double pyramid1 composed of three interpenetrating crystals1 typical of witherite and strontianite #cbh ,plate #di4--;,apatite crystals in crystalline calcite4 ,the ends of apatite crystals showing common modes of termination 7in color7 #cjf ,plate #ej4--;,a group of fluorite crystals4 ,a group of halite crystals 7in color7 #cjg ,plate #ea4--,sulphur crystals4 ,ice crystals1 the top one1 the end of a hexagonal prism2 the two lower figures multiple twins as in snow flakes #ccc ,plate #eb4--,the ,devil's ,tower1 ,wyoming1 an example of igneous rock with columnar structure1 and resting on sedimentary rocks #ccd ,courtesy of the ,u4 ,s4 ,geological ,survey ,plate #ec4--;,a coarse granite4 ,graphic granite #cce ,plate #ed4--,syenite4 ,gabbro #ccf ,plate #ee4--;,basalt-porphyry4 ,the large white crystals are phenocrysts of plagioclase feldspar4 ,basalt-obsidian #ccg ,plate #ef4--;,amgydoloid #cch ,plate #eg4--,the north face of ,scott's ,bluff1 ,neb41 showing sedimentary sandstones above and clays below4 ,the type of erosion is characteristic of arid regions #cci ,courtesy of the ,u4 ,s4 ,geological ,survey ,plate #eh4--;,breccia4 ,conglomerate #cdj ,plate #ei4--;,calcareous shale4 ,coquina #cda ,plate #fj4--;,foramenifera from chalk2 enlarged about #be diameters4 ,encrinal limestone2 fragments of the stems1 arms and body of crinoids #cdb ,plate #fa4--;,amber4 ,two bottles of petroleum1 the left hand one with a paraffin base1 the right hand one with an asphalt base 7in color7 #cjh ,plate #fb4--;,diatomaceous earth magnified #ej times4 ,two diatoms from the above enlarged #bej times #cdc ,after ,gravelle1 by the courtesy of ,natural ,history ,plate #fc4--;,a metamorphic rock1 showing the contortion of layers due to expansion under heat #cdd ,plate #fd4--;,a conglomerate partly metamorphosed to a gneiss4 ,a typical gneiss #cde ,plate #fe4--,mica schist1 with garnets4 ,chlorite schist 7in color7 #cji ,plate #ff4--,phyllite4 ,a white marble1 with black streaks due to graphite #cdf ,plate #fg4--,serpentine composed of serpentite1 hematite1 and some calcite 7in color7 #caj ,plate #fh4--;,claystones1 simple and compound4 ,a lime concretion1 which on splitting disclosed a fern leaf of the age of the coal measures #cdg ,plate #fi4--;,a septeria from ,seneca ,lake1 ,n4 ,y4 ,pisolite from ,nevada #cdh ,plate #gj4--;,a geode filled with quartz crystals #cdi ,plate #ga4--;,a quartz pebble from the bed of a ,new ,england brook4 ,a pebble of schist and granite from the foot of ,mt4 ,toby1 ,mass4 #cej ,plate #gb4--;,an iron-nickel meteorite1 of #bc lbs41 which fell in ,claiborne ,co41 ,tenn4 ,an etched slice of an iron meteorite which fell in ,reed ,city1 ,osceola1 ,co41 ,mich4 #cea ,plate #gc4--;,a stone meteor1 about natural size1 which fell in #ahge in ,iowa ,co41 ,iowa #ceb ,,field ,,book ,,of ,,common ,,rocks ,,and ,,minerals ,,chapter ,i ,,an ,,introduction ,why ,why should one be interested in rocks and minerals8 ,because the whole world is made of rocks and minerals4 ,they are the foundations on which we build4 ,from them we draw all our metals1 and the extent to which we utilize our minerals is a measure of the advance of our civilization4 ,fragments of rock are the soil from which1 by way of the plants1 we draw our food1 and ultimately our life4 ,the rocks make wild or gentle scenery1 one at least of the sources of pleasure4 ,knowledge of rocks and minerals is then knowledge of fundamentals1 of ultimate sources4 ,between finding the raw materials and their present uses there are usually many steps 7so many that we forget that the beginning and end are united71 as for instance in your watch4 ,it is made of gold1 brass1 steel1 agate1 glass1 and perhaps has luminous radium paint on the hands4 ,it is a long way from finding and mining gold1 chalcopyrite1 hematite1 carnotite1 etc41 through the raw materials1 gold1 copper1 iron1 etc41 to the finished watch1 but the minerals are the foundations of the watch2 and it took centuries to find them and learn one by one how to use them1 from the gold #aj1jjj years ago down to the radium within the last fifty years4 ,then too there is joy in going out into ,nature's wild and raw places1 joy in being on the foundations of the earth1 joy in the scenery1 in the beauty of the minerals themselves4 ,but why collect the rocks and minerals8 ,first because this is the way to know them4 ,both mineral and rocks require careful examination in order to see all those fine points by which they are distinguished4 ,it is often necessary to compare one with another to get in mind the differences of form1 color1 streak1 though with increasing familiarity these characteristics are recognized at first sight4 ,it is the repeated examination which makes a rock tell the story of the country from which it came4 ,our first attempts to read the story give us only the most general facts4 ,nature's book1 written in the rocks1 has to be read closely1 often between the lines4 ,until we are used to the characters in which the words are written1 we read slowly4 ,when they look at ,nature's book1 always open1 most people do not read2 for they do not know their letters4 ,every mineral is a letter1 every rock a word1 and we learn to read as we learn the minerals and rocks1 and every time we go over them we get more facts coming out4 ,the place where a rock or mineral occurs is of course the relation between them1 and is involved in reading the story4 ,no one today is a perfect reader4 ,we are all learning to see more in the rocks day by day4 ,so it is important to have the rocks and minerals where they can be handled and repeatedly examined1 where we can turn to them in our leisure moments4 ,don't stop when you have learned the name of a mineral or rock4 ,you need more4 ,see what it means4 ,secondly1 minerals have beauties of form1 color1 and structure1 and they do not fade4 ,they will be as perfect in ten years as when found4 ,we are all naturally crows1 and love to gather the objects which interest us4 ,it is not a bad habit1 and only needs directing4 ,cultivate it4 ,have a hobby1 and minerals and rocks are a good one2 for they are like treasures in ,heaven which 8neither moth nor rust doth corrupt40 ,not only will they give you pleasure1 but they will be a constructive education1 training the eye to see1 and the mind to think straight4 ,no one ever regretted the time and effort spent in collecting either minerals or rocks4 ,collecting ,in order to make a collection valuable two or three rules must be observed4 ,in the case of rocks1 collect large enough samples so that they will be characteristic1 and clear in their make-up4 ,the standard size for rocks is #c #d inches on top and one to two inches thick according to the nature of the rock4 ,tiny fragments do not give the character of the rock as well1 and they are all the time getting into confusion4 ,every specimen should be labeled1 with at least its name and the exact locality from which it came4 ,composition1 structural features1 associations1 and classification may be added1 the more the better2 for each item adds to the information and interest of the specimen4 ,one may make his own labels or have printed blanks1 and may put as much care and art into the labels as desired1 the more the better4 ,one thing is very important and that is to have a number on the label with a corresponding one on the specimen1 so that in case they should get separated1 they may be readily brought together1 even by one who is not familiar with the individual specimens4 ,lastly1 give your collection as good a place as possible1 either in drawers1 boxes or in a case4 ,the specimens are worth being kept in order and where they can be readily seen and compared4 ,nature is systematic1 and there is a reason for the order in which rocks and minerals are taken up4 ,it is desirable either that this order1 or some one of the orders of ,nature appear in the collection4 ,in this book the metals are the basis of classification1 all those minerals primarily related to one of the metals being grouped together4 ,in collecting minerals1 the size of the specimens can not be so regularly followed1 but it should be followed when collecting non-crystalline minerals1 and when possible4 ,crystals however are chosen from a variety of points of view1 as perfection of form1 color1 examples of cleavage1 twinning1 etc42 so that in many cases smaller or larger examples must appear in the collection4 ,it is always desirable that as many variations of a rock or mineral as possible should appear in the collection1 and in many cases examples of the matrix from which the crystals came4 ,when crystals are tiny1 it is well to place them in vials1 that they may not be lost4 ,where ,where shall we start in making a collection8 ,near home4 ,get the local minerals and rocks first1 and then range as widely as possible4 ,the best places are bare and exposed rocks1 especially where fresh and un-weathered surfaces are available4 ,quarries and where there has been blasting along roads offer fine opportunities4 ,fissures and cavities in the rocks are especially likely to have fine crystals1 and in all localities continued search will reveal a surprising number of different minerals4 ,the greatest variety occur in metamorphic rocks1 or where igneous rocks come in contact with other rocks1 but even the sedimentary rocks have a goodly range of minerals4 ,all through the glaciated regions of the northern ,united ,states lie scattered boulders brought from afar1 which will yield a surprising number of minerals and variety of rocks4 ,equipment ,one may start with a very simple equipment1 a geologist's or stone mason's hammer which can be obtained at any hardware store1 being sufficient for field work4 ,rocks should be broken1 so as to show fresh surfaces and to get below the disintegrating effects of weathering4 ,at home one should have a streak plate 7a piece of unglazed porcelain71 a set of hardness minerals 7see page #bj71 and a small bottle each of hydrochloric and nitric acid4 ,a pocket lens is useful in order to see more clearly the form of small minerals4 ,these things can be purchased of any ,naturalist's ,supply ,co41 like ,ward's ,natural ,science ,establishment1 ,p4,o4 #bd1 ,beachwood ,sta41 ,rochester1 ,n4 ,y41 or the ,kny-,scheerer ,corp41 #dhc ,first ,ave41 ,new ,york ,city4 ,success depends upon a quick eye1 and persistent hunting4 ,when traveling1 opportunities are offered at frequent intervals to see and get new specimens4 ,study ,your ,collection ,be sure and see the meaning in each rock and mineral4 ,the history of the country is revealed in its rocks and minerals4 ,note whether the rocks are horizontal or folded1 whether they change character from place to place1 or vertically4 ,in going over a piece of country you may locate an ancient mountain system now leveled1 by noting a series of metamorphic rocks1 with a central core of granite1 the roots of former mountains4 ,don't be afraid to draw conclusions from what you see4 ,later1 when the opportunity offers1 look up the region in the geological folio1 bulletin1 or map of that section1 and check up your findings4 ,these geological folios and bulletins1 of which there is one for nearly every region1 are a great help to collectors in suggesting where to look for various rocks and minerals4 ,write to the ,director of the ,u4 ,s4 ,geological ,survey1 ,washington1 ,d4 ,c41 for a catalogue of the publications of the ,united ,states ,survey1 or find out from him what are the maps or folios for the region in which you are interested4 ,these ,u4 ,s4 publications cost but little4 ,when opportunity presents itself1 visit other collections4 ,in them you will see some of the minerals or rocks which have puzzled you1 and there is nothing quite so satisfactory as seeing the rocks or minerals themselves4 ,no description can always be so convincing4 ,then too you will get suggestions as to localities that you can visit4 ,literature ,as your collection grows1 if you find you have special interest in one or another branch of the field1 you can get books giving more details in that line2 and at the back of this book will be found a list of such books4 ,,chapter ,,ii ,,on ,,the ,,forms ,,and ,,properties ,,of ,,minerals ,rocks ,all we know of the earth by direct observation is confined to less than four miles depth2 though by projecting downward the layers of rock that come to the surface1 we may fairly assume a knowledge of the structure down to six or eight miles depth4 ,this outer portion is often referred to as the 8crust of the earth10 but the idea that the deeper portions are molten is no longer held4 ,this outer portion is made of rocks1 and a rock may be defined as1 a mass of material1 loose or solid1 which makes up an integral part of the earth1 as granite1 limestone1 or sand4 ,the rocks 7except glassy igneous ones7 are aggregates of one or more minerals2 either in their original form like the quartz1 feldspar and mica of granite1 or in a secondary grouping1 resulting from the units having been dislodged from their primary position and regrouped a second time1 as in sandstone or clay4 ,minerals ,since the rocks are aggregates of minerals1 it is best to take up the minerals first4 ,a mineral may be defined as a natural inorganic substance of definite chemical composition4 ,it is usually solid1 generally has crystalline structure1 and may or may not be bounded by crystal faces4 ,a crystal is a mineral1 bounded by symmetrically grouped faces1 which have definite relationships to a set of imaginary lines called axes4 ,there are between #aajj and #abjj minerals1 of which #cj are so frequently present1 and so dominant in making up the rocks1 that they are termed rock-forming minerals4 ,about #aej more occur frequently enough so that they can be termed common minerals1 and one may expect to find a fairly large proportion of them4 ,some of these are abundant in one part of the country and rare in others1 but this book is written to cover the ,united ,states1 and so all those which have a fair abundance are included1 though some will only be found in the west and others mostly in the east4 ,then there are some more minerals which are really rare1 but which are cherished because of their beauty of color1 and are used as gems4 ,these are mentioned1 and many of the gems are simply clear and beautiful examples of minerals1 which in dark or cloudy forms are much more common4 ,if one finds any of these rare minerals which are not mentioned in this book1 he must turn to one of the larger mineralogies mentioned in the literature list to determine them4 ,crystal ,structure ,a crystal is a mass of molecules1 all of the same composition4 ,a molecule in its turn is made up of atoms1 and each atom is a unit mass of an element4 ,thus the calcite molecule is made up of one unit or atom of calcium1 one of carbon1 and three of oxygen 7,ca,c,o74 ,these atoms are held together by an attraction1 and make a molecule1 and for the study of minerals the molecule is the unit4 ,the mineral1 calcite1 is a mass of molecules all like the one above1 and each molecule so small as to be invisible even with the aid of the most powerful microscope4 ,when calcite is in crystal form1 the molecules1 like ranks of soldiers1 are arranged each in its place1 each at a definite distance from the other4 ,while each molecule may vibrate or wiggle within certain limits it does not leave its place4 7,the comparison with soldiers is a good one for the molecules of one layer1 but it must be remembered that in a crystal there are also like spacings and ranks up and down as well47 ,as long as the molecules remain in fixed ranks1 up and down1 forward and back1 and sideways1 the crystal is perfect4 ,calcite may be heated until it melts and becomes liquid4 ,then the molecules leave their definite arrangement and move about in all sorts of directions1 like the soldiers after ranks have broken4 ,so long as the molecules are thus free to move about but keep together1 the substance is a liquid4 ,there are cases when the molecules in this disorder take fixed positions without falling into ranks4 ,such minerals are non-crystalline and usually appear glassy4 ,if still greater heat is applied to the mineral in liquid form1 a point is reached 7the vapor point71 above which the molecules go flying away from each 7like soldiers in a panic71 each seeking to get as far from the other as possible1 so only a container will prevent their dissipation4 ,when in this condition a mineral is gaseous4 ,when cooled1 the reverse order obtains4 ,the molecules of gas gather into a miscellaneous mob or liquid3 and if this is further cooled 7but not too suddenly71 they fall into ranks and make a crystal4 ,this may be illustrated with water4 ,when above #bab ,f4 it is steam 7molecules wildly dissipated72 when between #bab and #cb it is water 7molecules close to each other1 but milling like a herd of cattle72 and when below #cb it is ice1 the molecules ranged in perfect order1 rank on rank4 ,crystal ,systems ,with all the possible forms that crystals can and do take1 there are six systems of arrangement4 ,first there is the case where ranks1 files1 and vertical rows are all equal1 and now to be scientific1 instead of talking about ranks1 files1 etc41 we use the term axes to express these ideas2 the files or arrangements from front to back1 being called the a axis1 the ranks1 or side to side arrangement the b axis1 and the vertical arrangement the c axis4 7,see ,plate #a47 ,these axes are imaginary lines1 but they represent real forces4 ,isometric system ,when the axes are all equal and at right angles to each other1 a crystal is said to be in the isometric system4 ,the cube is the basal form and each side is known as a face4 ,the ends of the axes come to the middle of the cube faces4 ,the essential feature of this system is that whatever happens to one axis must happen to all1 which is another way of saying that all the axes are equal4 ,if we think of the cube as having the corners cut off1 we would have a new face on each of the eight corners1 in addition to the six cube faces4 ,then if each of these new faces were enlarged until they met and obliterated the cube faces1 an eight-sided figure1 the octahedron1 would result4 ,in this the axes would ran to the corners4 ,another modification of the cube would be to bevel each of its twelve edges1 making twelve new faces in addition to the six cube faces4 ,if we think of these new faces being developed until they meet and obliterate the cube faces1 there will result a twelve-sided figure1 the dodecahedron4 ,and the #bd edges of the dodecahedron could be beveled to make a #bd-sided figure1 and so on4 ,of course in ,nature the corners are not cut1 nor the edges beveled1 but as a result of the interaction of the forces expressed by the axes and the distribution of the molecules1 the molecules arrange themselves in a cube1 octahedron1 dodecahedron or combination of these basal forms4 ,crystal formation ,crystals are formed in liquids as they cool or evaporate and can no longer hold the minerals in solution4 ,crystals start about a center or nucleus1 and molecule by molecule1 the orderly arrangement is increased and the crystal grows1 there being no size which is characteristic4 ,if free in the liquid the crystal grows perfectly on all sides1 but if crystals are growing side by side1 there comes a time when they interfere with each other4 ,then the free faces continue to grow and the orderly internal arrangement is maintained1 though externally there is interference4 ,tetragonal system ,in the second or tetragonal system one axis 7the c axis7 is different from the other two1 but all three are still at right angles with each other4 ,this is saying scientifically that the lines of force are greater or less in one direction than in the other two1 but they act at right angles to each other4 ,the a and the b axes are equal and anything that happens to one of these two must happen to the other1 but need not happen to the c axis4 ,thinking of the molecules that arrange themselves under this system of forces1 it is clear that the simplest form will be a square prism1 i4e41 front to back1 and from side to side the numbers of molecules will be equal1 but up and down there will be a greater or lesser number4 ,if the eight corners of this prism were cut1 and these corner faces increased in size until they met1 the resulting octahedron would be longer 7or shorter7 from top to bottom than from side to side or front to back1 but the measurement from front to back would be equal to the one from side to side4 ,in this system we may have the vertical edges of the prism beveled1 and not have to bevel the horizontal ones1 or we may bevel the horizontal edges and not the vertical ones4 ,there is no dodecahedron in this system or in any other system than the isometric4 ,the forms in this tetrahedral system are really a combination of the four sides of the square prism with such modifications as equally affect them all1 with two ends which may be flat1 or pyramidal1 or modified pyramidal faces4 ,orthorhombic system ,the third system has all three axes unequal1 but all three are still at right angles with each other4 ,this is saying that the lines of force in the crystals are all at right angles to each other but of unequal value4 ,the faces in this case are all in pairs4 ,what happens at one end of an axis must happen at the opposite end1 but does not need to happen at the ends of any of the other axes4 ,we are dealing with pairs of faces 7one at either end of an axis71 and if three such pairs are combined in the simplest manner1 the resulting figure will be a rectangular prism4 ,if we cut the eight corners of this prism and enlarge the faces until they meet1 the result is an octahedron1 in which the distance from top to bottom1 from side to side1 or from front to back is not the same in any two cases4 7,see ,plate #b47 ,in this system if a face is made by beveling one edge of the prism there must be a corresponding face on the edge diagonally opposite1 but there does not have to be one on any of the other edges4 ,however if a corner is cut1 that face affects all the axes and so all the corners must be cut4 ,a great many crystals occur in this system1 and some of them which are prismatic in shape may give trouble1 for it is not uncommon for the vertical edges of the prism to be so beveled1 that two of the original prism faces are obliterated1 and the two remaining faces added to the four new faces make a six-sided prism1 which at first glance seems to belong to the hexagonal system4 7,see ,plate #c1 fig4 #c47 ,close examination however will show that1 instead of all the prism faces being alike1 as would be necessary for the hexagonal system1 they are really in pairs1 and one pair at least will be distinguished in some way1 such as being striated1 pitted1 or duller4 ,monoclinic system ,the fourth system has all the axes unequal1 the a axis and the b axis at right angles to each other1 but the c axis is inclined to the a axis1 meeting it at some other than a right angle4 ,the monoclinic system is like the orthorhombic system except that it leans1 or is askew1 in one direction4 ,the result is that the faces at the ends of the b axis are rhombohedral1 while the others are rectangular4 ,as in the foregoing system1 the faces are in pairs at opposite ends of the axes2 and as in the orthorhombic system1 a face may occur on one edge and only have to be repeated on the edge diagonally opposite4 ,the simplest form in this system will be made by combining the three pairs of faces at the opposite ends of the axes1 which gives a prism1 which is rectangular in cross section1 but leans backward 7or forward7 if placed on end4 ,as in all the systems1 if a corner is cut1 all must be cut2 and if these corner faces are extended to meet each other1 an octahedron results1 in which1 as in the prism1 no two axes are equal4 ,if this octahedron is properly orientated 7i4e4 with the a and b axes horizontal71 it will lean forward or backward4 ,many minerals belong to this system2 and1 as in the orthorhombic system1 it is not uncommon to have the vertical edges so beveled that two of the prism faces are obliterated1 and the remaining two prism faces with the four new faces make a six-sided prism1 which seems hexagonal4 7,see plate #c1 figure #c47 ,however1 such a pseudo-hexagonal prism may be recognized by at least one pair of the faces having distinguishing marks 7stri1 pits1 or dullness71 instead of all being just alike4 ,triclinic system ,the fifth or triclinic system has all the axes unequal1 and no two of them intersect at right angles4 ,as in the two preceding systems the faces occur in pairs at the opposite ends of the axes4 ,this is the most difficult system in which to orientate a crystal1 but fortunately only a few crystals occur in this system1 such as the feldspars4 ,hexagonal system ,lastly there is a group of crystals which have four axes1 one vertical1 and three in the horizontal plane which intersect each other at angles of #fj1 all these three being equal to each other1 but different from the vertical axis4 ,the simplest form in this system is the six-sided prism4 ,if one corner of this prism is cut all must be1 and if these corner faces are extended to meet each other1 a double-six-sided pyramid results4 ,in this system if one of the vertical edges of the prism is beveled1 all must be1 but the horizontal edges need not be2 or the horizontal edges may be beveled and the vertical ones not4 ,the ends as they are related to the c axis may be developed independently of the prism1 and so the prism may be simply truncated by a flat end1 or have pyramids on either end4 ,hemihedral forms ,in this system it is quite common to have forms which result from the development of each alternate face of either the prism or the double pyramid4 ,in the case of the prism1 if every alternate face is developed 7and the others omitted7 a three-sided prism results1 as in tourmaline4 ,in the case of the double pyramid if the three alternate faces above are united with the three alternate faces below1 a six-sided figure is formed1 which is known as the rhombohedron1 as all the faces are rhombohedral in out-line and all equal4 ,these forms in which only half the faces are developed are known as hemihedral forms4 ,the same sort of thing may happen in the isometric system in the case of the octahedron1 and also in the case of the octahedron of other systems4 ,when half the faces of the octahedron are developed1 two above unite with two below and make a four-sided figure1 known as a tetrahedron4 7,see plate #aj47 ,while tetrahedrons may occur in any of the first five systems they are not common outside the isometric system4 ,twinning ,another modification of the simple forms which will be met occasionally is twinning4 ,by this is meant two crystals growing together as though placed side by side on some one of the faces1 and then revolved until the two axes which would normally be parallel are at some definite angle with each other1 #fj1 or #ahj which is commoner4 ,the surface of contact between the two crystals is called the composition face1 and as no more material can be added on that face the crystals continue to grow developing the other faces1 and we find faces in contact with each other which should be at the opposite end or other side of the crystals4 ,this contact of faces which should not come in contact1 and the presence of reentrant angles are indications of twinning4 ,in some minerals the twinning may be repeated time and again1 and if the twinning is on one of the end faces a branching structure results1 as in frost and snow crystals1 or the multiple twinning may be of crystals growing side by side when the final form will approximate a series of thin sheets placed side by side as in some feldspars4 ,the peculiar forms characteristic of individual minerals are taken up under the respective minerals4 ,other important properties of minerals are hardness1 cleavage1 specific gravity1 streak1 luster1 and color4 ,hardness ,hardness may be defined as the mineral's resistance to abrasion or scratching4 ,it is measured by comparing a mineral with ,moh's scale1 a set of ten minerals arranged in the order of increasing hardness1 as follows3 #a talc #b gypsum #c calcite #d fluorite #e apatite #f feldspar #g quartz #h topaz #i corundum #aj diamond ,a set for measuring hardness may be purchased from any dealer in mineral supplies4 ,for rough determination1 as in the field1 the following objects have the hardness indicated2 the finger nail #b1 a penny #c1 a knife blade about #e4e1 and glass not over #f4 ,in testing1 a mineral is harder than the one it will scratch1 and softer than the one by which it is scratched4 ,for instance1 if a mineral will scratch calcite and is scratched by fluorite1 it is between #c and #d in hardness1 say #c4e4 ,when two samples mutually scratch each other they are of equal hardness4 ,care must be used in determining hardness1 especially with the harder minerals2 for often1 when testing a mineral1 the softer one will leave a streak of powder on the harder one1 which is not a scratch4 ,one should always rub the mark to make sure it is really a groove made by scratching4 ,cleavage ,cleavage is the tendency1 characteristic of most minerals1 and due to the arrangement of their molecules1 to cleave or break along definite planes4 ,the cleavage of any mineral is not irregular or indefinite1 but characteristic for each mineral1 and always parallel to possible or actual faces on the crystal1 and always so described4 ,for instance galena has three cleavages1 all equally good1 and parallel to the cube faces2 so it is said to have cubic cleavage4 ,in the same way fluorite has octahedral cleavage1 and calcite rhombic cleavage4 ,in some minerals cleavage is well developed in one plane1 and less developed in other planes1 or it may be lacking altogether4 ,the varying degrees of perfection by which a mineral cleaves are expressed as1 perfect or imperfect1 distinct or indistinct1 good or poor1 etc4 ,specific gravity ,the specific gravity of a mineral is its weight compared with the weight of an equal volume of water1 and is therefore the expression of how many times as heavy as water the mineral is4 ,for instance the specific gravity of pyrite is #e4a1 which is saying it is #e4a times as heavy as water4 ,in a pure mineral the specific gravity is constant1 and an important factor in making final determinations4 ,as ordinarily obtained1 a piece of pure mineral is weighed in air1 which value may be called x4 ,it is then immersed in water and again weighed1 and this value is called y4 ,the difference between the weight in air and that in water is the weight of an equal volume of water4 ,then we have the following formula3 specific gravity 7x7_/7x-y74 ,various balances have been devised for making these measurements1 but any balance which will weigh small objects accurately1 may be adapted to specific gravity work1 by hanging a small pan under the regular weighing pan4 ,when using this balance1 care is taken to see that the lower pan is always submerged in water1 even while the mineral is being weighed in air1 so that when weighed in water in the lower pan1 the weight of this lower pan has already been considered4 ,streak ,by streak is meant the color of the mineral when powdered4 ,for some minerals1 especially metallic ores1 it is of great importance1 for it remains constant1 though the color of the surface of the mineral changes materially4 ,it is most readily determined by rubbing a corner of the mineral on a piece of unglazed porcelain4 ,small plates1 known as 8streak plates0 are made for this purpose4 ,luster ,the luster of a mineral is the appearance of its surface by reflected light1 and it is an important aid in determining many minerals4 ,two types of luster are recognized2 metallic1 the luster of metals1 most sulphides and some oxides1 all of which are opaque on their thin edges2 and non-metallic1 the luster of minerals which are more or less transparent on their thin edges1 and most of which are light colored4 ,the common non-metallic lusters are2 vitreous1 the luster of glass2 resinous1 the appearance of resin2 greasy1 oily appearance2 pearly1 the appearance of mother-of-pearl2 silky1 like silk due to the fibrous structure2 adamantine1 brilliant like a diamond2 and dull1 as is chalk4 ,color ,when used with caution color is of the utmost importance in determining minerals1 especially in making rapid determinations4 ,in metallic minerals it is constant and dependable2 but in the non-metallic minerals it may vary1 due to the presence of small amounts of impurities which act as pigments4 ,color depends on chemical composition1 and when not influenced by impurities is termed natural2 but when the color is due to some inclosed impurity it is termed exotic4 ,in this latter case caution must be used in making determinations4 ,many minerals are primarily colorless1 but take on exotic colors as a result of the presence of small quantities of impurities2 for instance1 pure corundum is colorless1 but with a trace of iron oxide present becomes red1 and is called the ruby1 or with a trace of cobalt becomes blue and is called sapphire4 ,,chapter ,,iii ,,the ,,minerals ,,key ,,to ,,the ,,minerals1 ,,based ,,on ,,hardness1 ,,color1 ,,etc4 ,,opaque ,,colors ,color ,hardness ,streak ,remarks ,mineral ,red scarlet #b4e scarlet surface tarnishes prousite black #b4e vermilion surface scarlet to cinnabar dark red ochre #g white non-crystalline jasper #f ochre red color red to hematite almost black rose #d white effervesces in rhodochrosite warm acid dark #d orange zincite #b4e purplish red surface tarnishes pyrargyrite black brownish #c4e brownish red cuprite ,orange #c4e white to pyromorphite yellowish #a-a orange realgar ,blue #e4e-f white in igneous rocks sodalite azure #d azure azurite sky #g #d4e white blade-like crystals cyanite turquoise #f blue non-crystalline turquois #b-d white chrysocolla ,green malachite #c4e lighter green malachite olive #f4e-g white in igneous rocks olivine #c4e white to yellow pyromorphite #b white mica-like cleavage chlorite #a white greasy feel1 color talc light to dark olive green yellowish #f4e white epidote #b4e-d white color yellow green serpentine to olive ,yellow golden #b4e shining non-crystalline gold brassy #f greenish-black usually crystalline pyrite #f greenish-gray color pale brassy marcasite yellow1 usually non-crystalline #e4e greenish-black colors nitric acid millerite green #d greenish-black color golden chalcopyrite similar to gold #c4e dark brown purplish tarnish tetrahedrite on surface bronze #e4e pale color with coppery niccolite brownish-black cast #d dark gray-black with speedy black pyrrhotite tarnish #c gray-black brownish with bornite bluish tarnish #b4e shining coppery red color copper sulphur #c4e white to compact masses pyromorphite yellowish #b yellow sulphur #a-c earthy masses carnotite ,brown violet #a shining tarnishes black cerargyrite yellowish #g4e white #d-sided prisms zircon #f4e gray cassiterite #e4e ochre yellow compact to earthy limonite masses #e brownish-yellow goethite #d4e black wolframite #c4e yellowish-brown sphalerite #c4e white siderite grayish #g4e white often twinned staurolite #f4e pale brown rutile #c4e white to earthy masses pyromorphite yellowish reddish #g white dodecahedrons garnet trapezohedrons ,black #f4e gray cassiterite #f reddish-brown franklinite #f black magnetic magnetite #e4e dark brown chromite #e4e black yellow precipitate wolframite in sulphuric acid #e-f black non-magnetic ilmenite #e-f brownish-black compact masses psilomelane #e brownish-yellow surface often goethite brownish #c4e dark brown tetrahedrons tetrahedrite #b4e silvery fresh surfaces silver silver color #b4e scarlet fresh surfaces prousite bright red #b4e purplish red fresh surfaces red pyrargyrite #b black earthy masses pyrolusite #a steel gray greasy feel graphite ,metallic #b4e black tarnishes black1 chalcocite ,gray bluish1 or green #b4e lead gray sectile argentite #b4e lead gray cubic cleavage galena #b lead gray long prismatic stibnite crystals #a4e bluish gray in scales molybdenite steel #e4e gray black rose color in smaltite nitric acid #d4e steel gray very heavy platinum #d reddish black often in striated manganite prisms #a gray with greasy feel graphite silvery #e4e black arsenopyrite #b4e silvery tarnishes black on silver exposure reddish #e4e gray black rose color in cobaltite nitric acid pearly #a-a shining exposed surfaces cerargyrite violet brown ,white1 with #d white porcelainous magnesite impurities masses1 effervesces in acid grayish #b white earthy masses1 kaolinite or greasy feel yellowish #a-c white earthy masses bauxite #a white greasy feel1 talc fibrous or scaly ,,transparent ,,or ,,translucent ,,colors ,color ,hardness ,remarks ,mineral ,colorless or with faint tinges of color due to impurities #aj in octahedrons diamond #i in hexagonal prisms corundum #h in hexagonal prisms topaz #g in three-sided prisms tourmaline #g in hexagonal prisms quartz #g non-crystalline chalcedony #g or #d4e cubes with beveled edges boracite #f non-crystalline1 pearly luster opal #e4e rhombohedrons willemite #e4e trapezohedrons analcite #e4e tufts of needle-like crystals natrolite #e4e sheaf-like bundles of crystals stilbite #e hexagonal prisms with basal cleavage apatite #e effervesces in acid smithsonite #e becomes jelly-like in acid calamine #d4e monoclinic prisms colemanite #d in cubes fluorite #c4e effervesces in acid1 but one cleavage aragonite #c4e effervesces in acid1 heavy cerrusite #c effervesces in acid1 rhomboidal calcite cleavage #c no effervescence1 but soluble in anglesite nitric acid #b4e in cubes tastes of salt halite #b soluble in water1 sweetish taste borax #b #a perfect cleavage1 and two imperfect gypsum cleaves at #ff with each other ,white or with faint tinges of color due to impurities1 such as pink1 bluish1 etc4 #g hexagonal prisms quartz #g non-crystalline chalcedony #g or #d4e cubes with beveled edges boracite #f non-crystalline1 pearly luster opal #f cleavage in #c directions1 good in #b feldspar and imperfect in the other #e4e short eight-sided prisms pyroxene #e4e long six-sided prisms amphibole #e4e trapezohedrons analcite #e4e tufts of needle-like crystals natrolite #e4e sheaf-like bundles of crystals stilbite #e4e rhombohedrons willemite #e effervesces in acid smithsonite #e becomes jelly-like in acid calamine #d4e #g cubes with beveled edges boracite #d4e monoclinic prisms colemanite #d effervesces in acid1 porcelainous magnesite #c4e-d effervesces in acid1 heavy1 red color strontianite in flame #c4e effervesces in acid1 heavy1 green witherite color in flame #c4e effervesces in warm acid1 rhomboidal dolomite cleavage #c4e effervesces in acid1 cleavage in one aragonite direction only #c4e effervesces in acid1 heavy1 does not cerrusite color flame #c-c4e no effervescence1 cleavage in three anhydrite directions at right angles #c effervesces in acid1 rhomboidal calcite cleavage #c tabular crystals1 heavy1 green color barite in flame #b-c cleaves in thin elastic sheets mica #b4e cleaves in cubes cryolite #b4e cubes1 soluble in water1 salty taste halite #b #a perfect cleavage1 and #b less perfect gypsum ones #b cleaves in thin non-elastic sheets chlorite #b soluble in water1 tastes sweet borax #a greasy feel talc ,green #i hexagonal prisms oriental emerald #h octahedrons spinel #g4e hexagonal prisms beryl #g three-sided prisms tourmaline #g dodecahedrons or trapezohedrons garnet #g non-crystalline prase or plasma #f4e-g non-crystalline1 olive color olivine #f4e yellow green color1 rather opaque epidote #f non-crystalline1 pearly luster opal #e4e short eight-sided prisms pyroxene #e4e long six-sided prisms amphibole #e hexagonal prisms apatite #d cubes fluorite #c4e effervesces in acid cerrusite #b4e-d somewhat greasy feel1 massive or serpentine fibrous #b in mica-like scales1 non-elastic chlorite #a greasy feel1 fibrous or scaly talc ,red #i hexagonal prisms ruby #h octahedrons spinel #g three-sided prisms tourmaline #g dodecahedrons or trapezohedrons garnet #g hexagonal rose quartz #g non-crystalline jasper or carnelian #f pearly luster fire opal #d cubes1 rose tints fluorite #b-c pink mica-like scales lepidolite ,blue #i hexagonal prisms sapphire #g #d4e blade-like crystals cyanite #f non-crystalline masses turquois #e4e-f in igneous rocks sodalite #d azure color azurite #c4e effervesces in acid1 heavy cerrusite #b-d earthy masses1 turquoise color chrysocolla ,violet #g hexagonal prisms amethyst #d cubes fluorite ,yellow #i hexagonal prisms oriental topaz #h octahedrons spinel #h hexagonal prisms topaz #d cubes fluorite ,brown #i hexagonal prisms corundum #h octahedrons spinel #g4e four-sided prisms zircon #g hexagonal prisms smoky quartz #g three-sided prisms tourmaline #g non-crystalline flint #f non-crystalline opal #e4e short eight-sided prisms pyroxene #e4e long six-sided prisms amphibole #b-c cleaves into thin sheets mica ,black #i hexagonal prisms corundum #h octahedrons spinel #g three-sided prisms tourmaline #e4e short eight-sided prisms pyroxene #e4e long six-sided prisms amphibole #b-c cleaves in thin sheets mica ,the ,gold ,group ,gold was undoubtedly the first metal to be used by primitive man2 for1 occurring as it did in the stream beds1 its bright color quickly attracted the eye1 and it was so soft1 that it was easily worked into various shapes1 which1 because they did not tarnish1 became permanent ornaments4 ,the metal is associated with the very earliest civilizations1 being found in such ancient tombs as those at ,kertsch in ,crimea and in northern ,africa and ,asia ,minor4 ,it was used in the cloisonn work of ,egypt #cjjj years ,b4,c4 ,in ,america the ,indians1 especially to the south1 were using it long before the continent was discovered4 ,of all the metals gold is the most malleable1 and its ductility is remarkable1 for a piece of a grain's weight 7less than the size of a pin head7 can be drawn out into a wire #ejj feet long2 and it can be beaten into a thin leaf as thin as _/ of an inch in thickness1 and thus a bit1 weighing only a grain1 can thus be spread over #ef square inches4 ,it forms very few compounds1 but has a considerable tendency to make alloys 7i4e41 mixtures with other metals without the resulting compound losing its metallic character74 ,in ,nature gold is never entirely pure1 but is an alloy1 usually with silver1 there being from a fraction of #a up to #cj of the silver with the gold1 the more silver in the alloy1 the paler the color of the gold4 ,australian gold is the purest1 having but about 4#c of silver in it1 while ,californian gold has around #aj and ,hungarian gold runs as high as #cj of silver4 ,another alloy fairly abundant in ,nature is that with tellurium1 such as calaverite 7,au,te7 which is a pale brassy yellow1 similar to pyrite1 but with the hardness of but #b4e4 ,another combination includes gold1 silver and tellurium1 sylvanite1 7,au,ag,te7 a silvery white mineral with a hardness of but #b4 ,such combinations are known as tellurides and the calaverite is mined as a source of gold at ,cripple ,creek1 ,colo41 while the sylvanite is one of the important ores of gold in ,south ,africa4 ,occasionally gold is also found alloyed with platinum1 copper1 iron1 etc4 ,jewelers make several alloys1 8red gold0 being #c parts gold and #a of copper1 8green gold0 being the same proportions of gold and silver1 and 8blue gold0 being the combination of gold and iron4 ,our gold coins are alloys1 nine parts gold and one of copper1 to give them greater durability4 ,most of the gold recovered from nature is found native1 i4e41 the pure metal1 or with some alloy4 ,gold ,au ,pl4 #e ,usually non-crystalline1 but occasionally showing cube or octahedral faces of the isometric system2 hardness #b4e2 specific gravity #ai4c2 color golden yellow2 luster metallic2 opaque4 ,gold is mostly found as the metal and is readily recognized by its color1 considerable weight1 hardness1 malleability1 and the fact that it does not tarnish4 ,it usually occurs in quartz veins in fine to thick threads1 scales or grains1 and occasionally in larger masses termed 8nuggets40 ,it is insoluble in most liquids so that when weathered from its original sites1 it was often washed down into stream beds1 to be found later in the sands or gravels1 or even in the sea beaches4 ,when thus found it is termed 8placer gold10 and its recovery is placer mining4 ,most of the original discoveries of gold have been in these placer deposits2 and from them it has been traced back to the ledges from which it originally weathered4 ,in the placer deposits the size of the particles varies from fine 8dust0 up to large nuggets1 the largest found in ,california weighing #afa pounds2 but the largest one found in the world was the 8,welcome ,nugget10 found in ,australia1 and weighing #bdh pounds4 ,when gold was discovered in ,california in #ahdh1 this became the chief source for the world1 but later this distinction went to ,australia1 and now belongs to ,south ,africa1 which today yields over half the annual supply4 ,the ultimate source of gold is from the lighter colored igneous rocks1 like granites1 syenites1 and diorites1 throughout which it is diffused in quantities too small to be either visible or worth while to extract4 ,it becomes available only when it has been dissolved out by percolating waters and segregated in fissures or veins1 either in or leading from these igneous rocks4 ,generally this transfer of gold has taken place when the rocks were at high temperatures1 and by the aid of water 7and perhaps other solvents7 which was also at high temperatures4 ,the presence of gold in sandstones1 limestones1 etc41 is secondary1 as is also its presence in sea water1 in which there is reported to be nearly a grain 7about five cents worth7 in every ton of water4 ,beside the direct recovery of gold from gold mining1 a great deal is obtained from its association with iron1 copper1 silver1 lead and zinc sulphides1 in which it is included in particles too fine to be visible1 but in quantities large enough to be separated from the other metals after they are smelted4 ,in the ,united ,states gold is found in the ,cordilleran region from ,california to ,alaska1 in ,colorado1 ,nevada1 ,arizona1 ,utah1 the ,black ,hills of ,south ,dakota1 and in small quantities in the metamorphosed slates of ,north and ,south ,carolina1 ,georgia1 and in ,nova ,scotia4 ,the ,silver ,group ,though much commoner than gold1 silver did not attract the eye of man as early1 probably because it tarnishes when exposed to air or any other agent having sulphur compounds in it1 and a black film of silver sulphide covers the surface4 ,its first use was for ornaments1 and some of these found in the ruins of ancient ,troy indicate its use as early as #bejj ,b4,c4 ,a thousand years later it was being used to make basins1 vases and other vessels4 ,silver is next to gold in malleability and ductility1 so that a grain of silver can be drawn out into a wire #djj feet long1 or beaten into leaves _/ of an inch in thickness4 ,as a conductor of electricity it is unsurpassed1 being rated at #ajj while copper rates #ic4 ,silver is also like gold in the freedom with which it alloys with other metals1 such as gold1 copper1 iron1 platinum1 etc4 ,all our silver coins1 tableware1 etc41 have some copper alloyed with the silver to give it greater hardness and durability4 ,unlike gold1 silver freely enters into compounds with the non-metals1 which is the reason that it is not found primarily in its native state1 but usually as a sulphide4 ,its ultimate source is in the igneous rocks1 few granites or lavas1 on analysis1 failing to show at least traces of silver4 ,before it is available as an ore1 or mineral1 it has been dissolved from the original magma1 and segregated in fissures or veins1 along with such minerals1 as quartz1 fluorite1 calcite1 etc4 ,this seems to have taken place while the igneous rocks were still hot1 and by the agency of vapors and liquids which were also hot4 ,the presence of silver in sedimentary and metamorphic rocks1 or even in sea water1 is secondary4 ,the primary deposition of silver is usually in the form of sulphides1 the commoner of which are1 argentite or silver sulphide1 pyrargyrite or silver and antimony sulphide1 and prousite1 or silver and arsenic sulphide4 ,its occurrence as native silver1 or the chloride1 cerargyrite1 is secondary and due to the reactions which have taken place when sulphide deposits have been subjected to weathering agents4 ,the ,united ,states produces about #be of the world's supply1 ,mexico some #ce4 ,it is especially found along the ,cordilleran ranges of both ,north and ,south ,america4 ,silver ,ag ,pl4 #f ,usually non-crystalline1 but occasionally showing cube or octahedron faces of the isometric system2 hardness #b4e2 specific gravity #aj4e2 color silvery white2 luster metallic2 opaque4 ,when found in its native state silver is usually in wirey1 flakey1 or mossy masses2 but sometimes masses of considerable size occur1 the most famous being an #hjj pound nugget found in ,peru1 and another of #ejj pounds weight found at ,konsberg1 ,norway1 and now preserved in ,copenhagen4 ,when exposed to the air the surface soon tarnishes and takes on a black color which must be scraped off to see the real color4 ,like gold1 silver is usually found associated with other metals1 like iron1 copper1 lead and zinc2 and much of the silver recovered is obtained in connection with the mining1 especially of copper and lead4 ,some lead ores have so much silver in them that they are better worth mining for the silver2 galena1 for instance1 under such circumstances being termed argentiferous galena4 ,native silver is a secondary mineral1 having been formed by the reduction of some one of its sulphides by water1 carrying various elements which had a greater affinity for the sulphur4 ,silver is found along with copper in the ,lake ,superior region1 and in ,idaho1 ,nevada1 and ,california4 ,argentite ,ag,s ,pl4 #f silver glance ,usually in irregular masses1 but sometimes in cubes2 hardness #b4e2 specific gravity #g4c2 color and streak lead gray2 luster metallic2 opaque on thin edges4 ,argentite1 the simple sulphide of silver1 is the chief source from which silver is obtained4 ,it looks like galena1 and has the same hardness1 streak and specific gravity1 but can be distinguished by the galena having a very perfect cubic cleavage while the argentite has no cleavage4 ,argentite is easily cut with a knife 7sectile74 ,it is usually found in irregular masses1 but sometimes in cubes which make very choice cabinet specimens2 and is associated with such other minerals as galena1 sphalerite1 chalcopyrite1 pyrite1 fluorite1 quartz1 and calcite4 ,it occurs in fissures and veins all through the ,cordilleran regions1 especially in ,california1 ,colorado1 ,nevada 7,comstock ,lode71 ,arizona 7,silver ,king ,mine7 and about the shores of ,lake ,superior4 ,pyrargyrite ,ag,sb,s ,pl4 #g ruby silver or dark red silver ,usually occurs in irregular masses2 hardness #b4e2 specific gravity #e4h2 color dark red to black2 streak purplish red2 luster metallic to adamantine2 translucent on thin edges4 ,pyrargyrite1 the sulphide of silver and antimony1 is distinguished by its dark red color and the purplish streak4 ,it may look like prousite1 but is easily distinguished from the latter which has a scarlet streak4 ,it also at times looks like hematite and cinnabar1 but the hematite has a hardness of #f1 and the latter has the bright red color throughout1 while pyrargyrite turns black when exposed to the light1 so that the characteristic red color will be seen only on fresh surfaces4 ,the characteristic red color can only be kept on the mineral if it is constantly protected from the light4 ,sometimes pyrargyrite occurs in crystals and these belong to the hexagonal system1 and are prisms with low faces on the ends1 as on plate #g1 and the mineral is peculiar in that the faces on the opposite ends are unlike4 ,pyrargyrite is found mostly in fissures and veins of quartz1 fluorite1 calcite1 etc41 and associated with pyrite1 chalcopyrite1 galena1 etc4 ,it is fairly common in ,colorado in ,gunnison and ,ouray counties1 in ,nevada1 ,new ,mexico1 ,arizona1 etc4 ,prousite ,ag ,as,s ,pl4 #g light red silver ,usually occurs in irregular masses2 hardness #b4e2 specific gravity #e4f2 color scarlet to vermilion2 streak the same2 luster adamantine2 transparent on thin edges4 ,in general this mineral is very like pyrargyrite1 but has the scarlet color and streak which are entirely characteristic4 ,it is likely to have the surface tarnished black1 which happens on exposure to light1 so that it is essential to be sure that fresh surfaces are being examined4 ,occasionally it is found in crystals1 of the same type as the preceding mineral4 ,it is generally found associated with pyrargyrite4 ,cerargyrite ,ag,cl horn silver ,usually found in irregular masses or incrustations2 hardness #a to #a2 specific gravity #e4e2 color pearly gray1 grayish green to colorless1 but turning violet brown on exposure to light2 luster resinous2 transparent on thin edges4 ,this mineral is usually found in thin seams or waxy incrustations1 but it may occur in crystals in which case they are cubes4 ,it is very soft and easily cut with a knife1 which with its tendency to turn violet-brown on exposure to light1 makes it easy to identify4 ,cerargyrite is a secondary mineral1 resulting from the action of chlorine-bearing water on some one of the sulphides of silver4 ,it is found in the upper portions of mines1 especially those in arid regions4 ,the ,copper ,group ,after gold the next metal to be utilized was copper4 ,about #djjj ,b4,c4 our early forefathers found that by heating certain rocks1 they obtained a metal which could be pounded1 ground and carved into useful shapes4 ,curiously enough the rocks which had the copper also had some tin in them1 so that this first-found copper was not pure1 but had from five to ten per cent of tin in it1 making the resulting metal harder1 and what we call bronze4 ,it was some thousands of years later before they distinguished the copper as a pure metal1 but it worked and made good tools4 ,the newly found metal was not as ornamental as gold2 but1 because it could be made into tools1 it had a tremendous influence on man's development4 ,as the bronze tools began to take the place of the stone implements1 the 8,age of ,bronze0 was ushered in4 ,in ,america the ,indians in the ,lake ,superior region found native copper weathered out of the rocks and later mined it1 and they too pounded it into knives1 axes1 needles1 and ornaments1 but probably never learned to melt it and mold their tools4 ,at any rate they were not as far advanced in using this metal when ,columbus landed as were the southern ,europeans #fejj years earlier4 ,since the use of iron became general1 copper has not held such a dominant place1 but it still is 8the red metal0 which holds the second most important place4 ,it is malleable and ductile1 though not equal to gold or silver in these respects4 ,it is a good conductor of electricity and a very large amount of copper is used in electrical manufacture1 roofing1 wire1 etc4 ,it alloys with other metals2 ten parts copper and one of tin being bronze1 ten of copper and one of zinc is brass1 and copper with aluminum is aluminum bronze4 ,like silver and gold1 copper is widely diffused through the igneous rocks1 but before it is available1 it must be leached out by solvents and concentrated in veins1 fissures1 or definite parts of the lavas or granites4 ,the primary ores are those which1 while the igneous rock was still hot1 were carried by hot vapors and liquids into the fissures and there deposited1 mostly as sulphides4 ,there is a long list of these1 but in this country1 the following are the commoner ones2 chalcocite the sulphide of copper1 chalcopyrite the sulphide of copper and iron1 bornite another combination of copper1 iron and sulphur1 and tetrahedrite copper and antimony sulphide4 ,when these primary ores are near enough to the surface to come in contact with waters carrying oxygen1 carbon dioxide or silica in solution1 they may give up their sulphur and take some one of these new elements and we have such forms as cuprite1 the oxide of copper1 malachite and azurite1 carbonates of copper1 or chrysocolla1 the silicate of copper4 ,native copper is also a secondary deposit laid down in its present state by a combination of circumstances which deprived it of its original sulphur4 ,in general copper mining can not be profitably carried on for ores with anything less than a half of one percent in them2 and the use of such low grade ores has only been possible for a few years1 as the result of inventing most delicate processes in the smelting4 ,the ,united ,states produces about a quarter of the world's supply of copper1 with ,chile ranking second with about #ag4 ,copper ,cu ,pl4 #h ,usually in irregular masses2 hardness #b4e2 specific gravity #h4i2 color copper red2 luster metallic2 opaque4 ,native copper1 easily determined by its color and hardness1 is generally found in irregular grains1 sheets1 or masses1 on which may sometimes be detected traces of a cube or an octahedral face1 showing that it belongs to the isometric system4 ,the most famous locality is the ,upper ,peninsula of ,michigan which may be taken as typical4 ,here1 long before it was known historically1 the ,indians found and dug out copper to make knives1 awls1 and ornaments4 ,in this region1 beds of lava alternate with sandstones and conglomerates4 ,the copper was originally in the lavas1 but has been dissolved out1 and now fills cracks and gas cavities in the lavas1 and also the spaces between the pebbles of the conglomerate4 ,this locality has been very famous both because of the quantity mined1 and also because of the strikingly large masses sometimes found4 ,today but little of the ore runs above #b percent copper1 and it is mined if it has as little as of one percent4 ,while nowhere near as abundant1 native copper occurs in the same way in cavities and cracks in the trap rocks of ,new ,jersey1 and along the south shore of the ,bay of ,fundy4 ,it is also known from ,oregon1 the ,white ,river region of ,alaska1 and in ,arctic ,canada4 ,chalcopyrite ,cu,fe,s ,pl4 #h copper pyrites or yellow copper ore ,occurs in crystals of irregular masses2 hardness #d2 specific gravity #d4b2 color bronze yellow2 streak greenish black2 luster metallic2 opaque on thin edges4 ,chalcopyrite resembles pyrite1 but its color is a more golden yellow1 and its surface tarnishes with iridescent colors4 ,then too the hardness of chalcopyrite is but #d as compared with #f for pyrite4 ,when in crystals this mineral belongs to the tetrahedral system as the c axis is but 4#ihe in length as compared with ,i for the two other axes4 ,this difference is so little that1 to the eye1 the octahedron appears to belong to the isometric system4 ,chalcopyrite occurs in octahedrons and tetrahedrons 7as on plate #h71 the latter being the form where but half of the octahedral faces are developed4 ,however by far the most frequent mode of occurrence is in irregular masses4 ,this is the most important primary ore of copper1 and is widely distributed1 being found either in lavas1 or in veins1 or in fissures connected with igneous rocks4 ,apparently the deposits were made1 either at the time of eruptive disturbances or shortly afterward1 from vapors or hot solutions carrying the copper sulphides 7and other sulphides7 from the molten igneous rocks4 ,chalcopyrite is usually associated with pyrite1 galena1 sphalerite and chalcocite1 as well as quartz1 fluorite and calcite4 ,it is found in all the ,new ,england ,states1 in ,new ,york1 ,new ,jersey1 ,pennsylvania1 ,maryland1 ,virginia1 ,north ,carolina1 ,tennessee1 ,missouri1 and all the ,rocky ,mountain and ,pacific ,coast ,states4 ,bornite ,cu,fe,s purple copper ore ,occurs in granular or compact masses2 hardness #c2 specific gravity1 #e2 color bronze-brown with a bluish tarnish2 streak gray-black2 luster metallic2 opaque on thin edges4 ,bornite is also known as erubescite1 blushing ore1 variegated copper1 peacock copper1 etc41 all of which names refer to the highly iridescent tarnish which fresh faces soon take on when exposed to the air4 ,though usually in masses1 it is sometimes found in rough cubes of the isometric system4 ,in this country it is not abundant enough to be used as an ore1 but is likely to be found with other ores like chalcopyrite or chalcocite4 ,in the east it has been found at ,bristol1 ,conn41 and near ,wilkesbarre1 ,penn41 while in the west it may be expected to occur wherever other sulphide minerals of copper are found4 ,chalcocite ,cu,s ,pl4 #i copper glance ,occurs in fine grained compact masses2 hardness #b4e2 specific gravity #e4g2 color dark leaden gray2 streak black2 luster metallic2 opaque on thin edges4 ,chalcocite is one of the important ores of copper1 especially in ,arizona and the ,butte ,district of ,montana4 ,it resembles argentite in color and general appearance1 but is readily distinguished by being brittle and having a tendency to tarnish to bluish or greenish colors on fresh surfaces4 ,occasionally it occurs in crystals which are in the orthorhombic system2 but the edges of the prism are so beveled that there are six sides and the prism resembles a hexagonal prism 7see page #af74 ,in the ,butte1 ,mont41 district1 the most important copper region in the ,united ,states1 fully #ej of the ore is chalcocite1 which is a derivative of the originally deposited chalcopyrite1 the latter having lost its iron4 ,in the veins of this district chalcopyrite1 bournite1 tetrahedrite1 and several other copper minerals not described in this book1 occur all together1 and with them also gold1 silver and arsenic minerals4 ,the gold amounts to about #b cents per pound of copper1 and the silver is in somewhat less quantity4 ,these veins were first opened to get the silver ores1 which were the more important ones down to a depth of #bjj to #djj feet4 ,below these depths the copper became much more important4 ,it was the weathering which had removed a large part of the copper minerals in the upper levels of the veins1 but had left a large part of the silver4 ,chalcocite is also important in most of the ,utah and ,arizona mines4 ,in the east it has been found at ,bristol1 ,simsbury and ,cheshire1 ,conn41 and in the west it is found in all the ,cordilleran ,states4 ,tetrahedrite ,cu,sb,s ,pl4 #i #aj gray copper ore ,occurs in irregular masses and in tetrahedrons of the isometric system2 hardness #c4e2 specific gravity #d4g2 streak dark brown2 luster metallic2 opaque on thin edges4 ,in its crystalline form the tetrahedrite occurs in tetrahedrons1 which generally have faces formed by beveling the edges and by cutting the corners1 as in the two figures of plate #aj4 ,chalcopyrite may also occur in tetrahedrons1 but its golden yellow color is entirely different from the gray-black of the tetrahedrite4 ,when in masses the hardness and the streak which is dark brown1 are very characteristic4 ,in ,england and ,bolivia tetrahedrite is an important ore of copper1 but in this country it is simply a copper mineral which is widely distributed1 and associated with most of the mining enterprises1 but is in no case the important ore4 ,it has been found sparingly through the ,new ,england ,states1 at the ,kellogg ,mines in ,arkansas1 and abundantly in ,colorado1 ,montana1 ,utah1 ,arizona1 ,nevada and ,new ,mexico4 ,cuprite ,cu,o ,pl4 #i #aj red copper ore ,occurs in isometric cubes1 octahedrons1 and dodecahedrons1 or in masses2 hardness #c4e2 specific gravity #f2 color dark brownish-red2 streak brownish-red2 luster metallic2 translucent on thin edges4 ,when in crystals cuprite is easily determined1 but when in masses its fresh surfaces may suggest prousite1 but the streak and hardness are quite different in the two cases4 ,sometimes its color suggests hematite1 but the latter has the hardness of #f4 ,when found it is often coated with a thin film of green1 which is malachite4 ,except when found as native copper1 the ore which contains the greatest percentage of copper is cuprite with #hh4h of copper4 ,it is likely to occur in any of the deposits of copper ore1 where they are in arid climates and above the level of the underground water1 and is very frequently associated with malachite and azurite4 ,in the ,bisbee1 ,arizona1 district cuprite is one of the important ores4 ,besides the normal occurrence described above1 cuprite may be found in two other varieties2 one where the crystals have grown side by side and so only the ends have been free for continuous additions of the mineral1 which has resulted in a fibrous mass known as 8plush copper ore0 or chalcotrichite2 the other an earthy mixture of limonite and cuprite1 which is brick red in color1 and termed 8tile ore40 ,cuprite is found sparingly in ,new ,england1 more abundantly at such places as ,summerville and ,flemington1 ,n4 ,j41 ,cornwall1 ,penn41 in the ,lake ,superior region1 and fairly abundantly in the ,cordilleran ,states4 ,malachite ,cu,c,o,cu7,,oh7 ,pl4 #aa ,usually occurs in nodular or incrusting masses2 hardness #c4e2 specific gravity #d2 color green2 streak a lighter green2 luster adamantine1 silky or dull2 translucent on thin edges4 ,the vivid green of malachite is usually enough to determine it at once1 but one may be sure by trying a drop of acid on it1 in which case it effervesces as is characteristic of so many carbonates1 but this is the only carbonate which is vivid green4 ,generally the malachite is in irregular masses1 but crystals are occasionally found4 ,these are extremely small and needle-like1 and belong to the monoclinic system4 ,in the ,ural ,mountains there is a locality where these crystals grow in fibrous masses1 usually radiating from the center4 ,malachite in such nodules has a silky luster4 ,these rare nodules have furnished the rulers of ,russia with a unique and much prized material for making royal gifts4 ,in ,european museums and palaces one finds many objects carved from this form of malachite1 and marked as gifts of the czars of ,russia4 ,in the ,united ,states malachite is widely distributed1 appearing as green streaks and stains where copper minerals have been exposed to the air4 ,it is the green tarnish which appears on bronze and copper when exposed to the weather4 ,it is found in large quantities in ,new ,jersey1 ,pennsylvania1 ,wisconsin1 ,nevada1 ,arizona1 ,utah1 ,new ,mexico1 etc4 ,the ,bisbee mine in ,arizona is the place that has furnished museums with so many of the handsome specimens of malachite associated with azurite4 ,these are the most striking specimens for the vividness of their colors that appear in any collections4 ,malachite has been known since about #djjj ,b4,c41 the ,egyptians having mines where they obtained it between the ,suez and ,mt4 ,sinai4 ,in those early days it was particularly a child's charm1 protecting the wearer from evil spirits4 ,it is still used as a stone of lesser value in making some sorts of jewelry4 ,azurite #b;,cu,c,o,cu7,,oh7 ,pl4 #aa ,occurs as short prismatic or tabular crystals of the monoclinic system2 hardness #d2 specific gravity #c4h2 color azure blue2 streak lighter blue2 luster vitreous2 translucent on thin edges4 ,azurite is another very striking mineral fully characterized by its color and streak4 ,like malachite it effervesces in acid4 ,it is very near to malachite in composition1 and by increasing its water content1 can and freely does change to the green mineral2 so that few specimens of azurite are without traces of malachite4 ,it is found in the same places as malachite1 but is not as abundant in the east4 ,azurite with the accompanying malachite is cut and polished to make semi-precious stones for some forms of jewelry4 ,chrysocolla ,cu,si,o#b;,h,o ,never occurs in crystals1 but in seams and incrustations2 hardness #b-d2 specific gravity #b4a2 color bluish-green2 streak white2 luster vitreous2 translucent on thin edges4 ,this rather rare mineral often appears in opal- or enamel-like incrustations1 and its color is variable ranging from the typical bluish-green to sky-blue or even turquoise blue4 ,this is a mineral resulting from the action of silica bearing waters1 coming in contact with most any of the copper minerals1 and is found accompanying cuprite1 malachite1 azurite1 etc4 ,it is never in large enough quantities to be used as an ore1 but its striking color attracts attention and it can be found fairly frequently1 especially in the west4 ,the ,iron ,group ,pure iron is a chemical curiosity which looks very much like silver4 ,as obtained from its ores1 or as it occurs in ,nature1 iron always has some impurities with it1 such as carbon1 silicon1 sulphur and phosphorus1 and these are highest in the crudest iron such as 8pig-iron40 ,its malleability and ductility are only a little less than for gold and silver1 and so it has a wide range of qualities for use by man4 ,it is only rarely found native in minute grains in some of the dark lavas4 ,there is however one remarkable exception to this statement1 in that on ,disco ,island1 ,greenland1 there is a basaltic rock1 from which are weathered great boulders of native iron up to #bj tons in weight4 ,this iron is very like that occurring in meteorites1 and probably came from great depths in the earth's interior4 ,the specific gravity of iron is #g4h4 ,it makes up around #e of the crust of the earth1 and probably occurs in much larger percentages in the interior of the earth4 ,iron was discovered by man later than gold or silver or copper1 about #ajjj ,b4,c42 but once found it was so much more abundant than any of these that it soon dominated over copper1 and from ,roman times to the present has been the basis of progress in civilization1 and these times are well called 8the iron age40 ,iron unites freely with the non-metals1 and occurs as sulphides1 oxides1 carbonates1 etc41 and is also present as a secondary metal in that great group of minerals known as the silicates 7see page #ig74 ,it alloys with a wide range of other metals1 every combination altering the properties of the iron1 and thus making it useful in a still greater range of manufacture4 ,the introduction of to #b of carbon into iron makes steel1 which is harder 7in proportion to the amount of carbon7 and stronger than the pure iron4 ,iron compounds are among the most numerous and important of the colors in ,nature's paint box1 limonite furnishing the browns which color the soil and so many of the rocks1 hematite giving the red color to other abundant rocks1 and magnetite often coloring igneous rocks black1 while the chlorophyll which gives the green color to plants is an iron compound1 as is also the hemoglobin which gives the red to our blood4 ,iron is present in all igneous rocks1 and secondarily in the sedimentary and metamorphic rocks4 ,it is soluble in water1 and so is being constantly transferred from place to place1 and changes from one compound to another1 according to the circumstances in which it is placed4 ,the primary forms are pyrite1 magnetite and the silicates4 ,when in weathered rocks the iron is changed to limonite1 siderite or hydrated silicates4 ,hematite is an intermediate oxide from which the water contained in limonite has been driven off by moderate heat or bacterial action4 ,limonite #b;,fe,o#c;,h,o ,pl4 #ab ,never crystalline1 occurs in mammillary1 botryoidal and stalactitic forms1 or in fibrous1 compact1 oolitic1 nodular or earthly masses2 hardness #e4e2 specific gravity #c4h2 color yellow-brown to black2 streak yellow-brown2 luster metallic to dull2 opaque4 ,limonite is a very common mineral1 the color1 streak and hardness identifying it readily4 ,iron rust is its most familiar form4 ,when powdered it is the ochre yellow used in paints4 ,being so universally distributed1 it is to be expected it will occur in a variety of ways4 ,first1 there is the fibrous type found lining cavities1 in geodes1 or hanging in stalactites in caves4 ,this has a silky luster1 an opalescent1 glazed or black surface1 and is in mammillated or botryoidal masses4 ,second1 it may occur in compact masses in veins1 where it was deposited by waters2 which1 circulating through the adjacent rocks1 gathered it from the rocks1 and1 on reaching the open seams1 gave it up again4 ,third1 it may occur in beds on the bottom of ponds1 where it was deposited by waters which gathered it as they flowed over the surface of the country rocks4 ,measurements in ,sweden show that it may accumulate in such places as much as six inches in the course of twenty years4 ,in ponds and swamps1 the decaying vegetation forms organic compounds1 which cause the precipitation of the iron from the water1 as it is brought in by the streams4 ,this sort of iron in the bottom of ponds or swamps is also known as 8bog iron40 ,another form in which limonite may occur in ponds1 lakes1 or even the sea1 is in oolitic masses4 ,in this case the iron forms in tiny balls1 with perhaps a grain of sand at the center1 and one coat of iron after another formed around it1 like the layers of an onion4 ,if the resulting balls are tiny this is called oolitic 7like fish eggs71 but if the balls are larger it is pisolitic 7like peas74 ,bacteria probably have a good deal to do with the precipitation of limonite in this manner4 ,fourth1 limonite occurs in earthy masses1 usually mixed with impurities like clay and sand1 which are the residue left behind1 where limestones have been dissolved by weathering4 ,the fifth mode of occurrence is known as gossan1 or 8the iron hat10 which is a mass of limonite capping a vein of some sulphide mineral1 like pyrite1 chalcopyrite or pyrrhotite1 which has been exposed to weathering2 and in these minerals the sulphur has been removed1 leaving a mass of limonite over the vein4 ,this is particularly common in the west4 ,limonite is quite easily fusible and so was probably the first ore from which early man extracted iron4 ,limonite is iron oxide1 with #c molecules of water of crystallization 7or constitution7 associated with every #b molecules of the oxide4 ,if limonite is moderately heated the water is driven out and the resulting compound is hematite1 the same oxide1 but without the water4 ,in this case and many other similar cases1 as gypsum1 opal1 etc41 we have two or more minerals resulting from the presence or absence of water in the mineral4 ,the water molecules have a definite place in the arrangement of molecules which determines the structure of the mineral4 ,sometimes the water is driven out at a temperature around #bab ,f41 in which case it is called1 water of crystallization1 but in other cases as gypsum1 a considerably higher temperature is required to drive out the water1 and then it is called1 water of constitution4 ,in all cases the removal of the water changes the arrangement of molecules and a new mineral results1 with characteristics of its own4 ,in this case limonite is only one of a series of minerals which have the ,fe,o molecule as a basis1 and that incorporate more or less water into their molecular construction as follows3 ,turgite #b;,fe,o,h,o ,goethite ,fe,o,h,o ,limonite #b;,fe,o#c;,h,o ,xanthosiderite ,fe,o#b;,h,o ,limonite ,fe,o#c;,h,o ,of these goethite is crystalline1 the others non-crystalline4 ,they may occur pure or in all sorts of mixtures1 the mixtures usually being lumped under limonite4 ,the limonite is far the commonest of the series1 goethite is fairly common1 but the others are rare as pure minerals4 ,limonite is found in all parts of all states and in every country4 ,though so common1 it is by no means an important source of iron today1 only about one percent of the iron mined in this country coming from this source1 though in ,germany1 ,sweden and ,scotland it is relatively much more important4 ,goethite ,fe,o,h,o ,pl4 #ab ,occurs in lustrous brown to black orthorhombic prisms1 usually terminated by low pyramids2 hardness #e2 specific gravity #d2 color brown to black2 streak brownish-yellow2 luster imperfect adamantine2 opaque4 ,goethite1 named for the poet ,goethe1 who was interested in mineralogy1 is much less abundant than limonite or hematite1 but occurs with them1 when they are in veins4 ,its usual form is an orthorhombic prism with the edges beveled1 and a low pyramid on either end4 ,the crystals usually grow in clusters1 making a fibrous mass1 often radiated1 in which case it is known as 8needle iron stone02 or the prisms may be so short as to be almost scales2 when1 because of the yellowish-red color1 it is called 8ruby mica04 ,it is found in many states1 including ,connecticut1 ,michigan1 ,colorado1 etc4 ,hematite ,fe,o ,pl4 #ac #ad specular iron ,occurs in compact1 mammillary1 botryoidal1 or stalactitic masses of dark red to black color1 or in earthy masses of bright to dark red2 hardness #f2 specific gravity #e4b2 color ochre red to black2 streak cherry red to dark red2 luster metallic1 vitreous1 or dull2 opaque on thin edges4 ,hematite is readily distinguished from other red minerals by its hardness and streak4 ,it may occur in crystals1 which belong to the hexagonal system1 and are usually hemihedral forms of the double pyramid1 or rhombohedrons4 ,these rhombohedrons usually have the edges beveled1 as in ,pl4 #ac1 ,a2 or are tabular in form as a result of the beveling of two of the opposite edges to such an extent that a form like ,pl4 #ac ,b results4 ,however the usual occurrence is in non-crystalline masses1 which represent transformations from limonite by the loss of water of crystallization on the part of the limonite4 ,in such cases we have fibrous1 oolitic or compact masses1 according to the form in which the limonite occurred4 ,the transformation from limonite into hematite involves some heat to drive out the water of crystallization1 but nothing like what is involved in metamorphism4 ,hematite is the source of #ij of the iron mined in this country4 ,part of it comes from the famous ,clinton iron ore1 a layer a foot or more in thickness2 starting in ,new ,york ,state1 and extending all down the ,appalachian ,mountains to ,alabama1 where it is ten or more feet thick and the basis of the ,birmingham iron industries4 ,then there are tremendous deposits of earthy to compact hematite1 probably derived from limonite1 around the west end of ,lake ,superior4 ,this latter region yields today around #ge of the iron for this country4 ,loose earthy masses of hematite are often known as 8ochre red10 and were used by the ,indians for war paint4 ,today the same sort of material is obtained by powdering hematite and using it for red paint4 ,the red color in great stretches of rock is due to the presence of small amounts of hematite1 acting as cementing material4 ,the red of the ruby1 garnet1 spinel1 and the pink of feldspars and calcite are due to traces of hematite4 ,this mineral is very common and found in every state4 ,magnetite ,fe,o ,pl4 #ad ,magnetic iron ore ,occurs in masses or in isometric octahedrons or dodecahedrons2 hardness #f2 specific gravity #e4h2 color black2 streak black2 luster metallic2 opaque on thin edges4 ,magnetite is another important ore of iron1 and is peculiar in being strongly magnetic2 its name being derived1 according to ,pliny1 from that of the shepherd ,magnes1 who found his iron pointed staff attracted by the mineral when he was wandering on ,mount ,ida4 ,this magnetic property has been repeatedly used to locate beds of magnetite1 and is very helpful in separating magnetite from the 8black sands10 of which it so often forms a part4 ,these sands however generally have magnetite with so much titanium in it that they are unfit for smelting4 ,magnetite is found in association with igneous or metamorphic rocks1 and often represents limonite or hematite which has been altered as the result of high temperatures4 ,some of it1 in the igneous rocks especially1 was undoubtedly in the molten magma and has crystallized out from the magma while it was still hot4 ,it is the form of iron always indicative of former high temperatures4 ,it is an ore mineral for about #c of the iron in this country1 but in ,scandinavia and some other countries1 it plays a leading role as the source of iron4 ,it is found in the ,adirondack ,mountains1 in ,new ,jersey1 ,pennsylvania1 ,arkansas1 ,north ,carolina1 ,new ,mexico1 and ,california4 ,siderite ,fe,c,o ,pl4 #ac #ad ,spathic iron ,occurs in fibrous botryoidal masses or rhombohedral crystals1 sometimes with curved faces2 hardness #c4e2 specific gravity #c4h2 color gray-brown2 streak white2 luster vitreous2 translucent on thin edges4 ,like hematite this mineral belongs to the hexagonal system1 and crystallizes in hemihedral form1 making the rhombohedron4 ,its faces are often curved1 which is rare in minerals1 only a few forms like this and dolomite having other than plane faces4 ,when siderite crystals grow in clusters1 the crowding often results in growth on one face only1 making a mass of fibrous character1 and in such cases the surface of the mass is botryoidal in contour4 ,the mineral is likely to oxidize1 losing its gray-brown color1 and becoming limonite4 ,in the ,united ,states it is scarcely ever used as an ore for iron1 but in ,germany and ,england a great deal of iron is smelted from this mineral4 ,it occurs in ,massachusetts1 ,connecticut1 ,new ,york1 throughout the ,appalachian ,mountains1 and also in ,ohio4 ,pyrite ,fe,s ,pl4 #ae #af iron pyrites ,occurs as cubes1 octahedrons and pyritohedrons1 or in compact masses1 scales or grains2 hardness #f2 specific gravity #e4a2 color brassy yellow2 streak greenish-black2 luster metallic2 opaque on thin edges4 ,this is one of the commonest of all minerals4 ,it is found in all kinds of rocks1 with all kinds of associations1 in all parts of the world4 ,its crystals are isometric1 and cubes and octahedrons are abundant4 ,the pyritohedron is also a common form1 and characteristic of this mineral4 ,it is a hemihedral form derived from a #bd-sided form1 i4e4 the cube with four faces on each side4 ,on this #bd-sided form each alternate face has developed and the others have disappeared1 resulting in a #ab-sided form1 known as the pyritohedron1 which differs from the dodecahedron in that each of its faces is five-sided instead of rhomboidal4 ,when in crystals pyrite can not be easily confused with any other mineral2 but when in masses it is often mistaken for gold1 chalcopyrite1 pyrrhotite or marcasite4 ,from the first two1 the color should be sufficient to distinguish it1 for they are golden yellow4 ,pyrrhotite is bronze yellow1 and marcasite is paler yellow4 ,then too in hardness pyrite is much harder than any of these minerals except marcasite4 ,this last is the one which is most likely to cause real difficulty4 ,its lighter color1 and the fact that it usually comes in fibrous masses are the best distinctions4 ,in spite of being so abundant pyrite is scarcely ever used as an ore for iron1 because the sulphur makes the metal 8short10 or brittle1 and the sulphur is not easily gotten entirely out of the iron2 but pyrite is used largely in the manufacture of sulphuric acid1 so important to many of our industries4 ,other sulphides are commonly mixed with pyrite1 such as chalcopyrite1 arsenopyrite1 argentite1 etc42 but the most important impurity is gold1 which is often scattered through the pyrite in invisible particles1 and sometimes in quantities enough to make it worth while to smelt it for the gold4 ,pyrite is particularly the form in which the sulphur compounds of iron appear in rocks which have been highly heated1 and is to be expected in metamorphic rocks and also igneous rocks1 especially in fissures and veins leading from the igneous rocks4 ,it may occur in sedimentary rocks1 but in these last it is usually marcasite4 ,marcasite ,fe,s ,pl4 #ae white pyrite ,occurs in orthorhombic crystals1 usually grouped to make fibrous or radiating masses1 or non-crystalline in masses2 hardness #f2 specific gravity #d4h2 color pale brassy-yellow2 streak greenish-gray2 luster metallic2 opaque on thin edges4 ,marcasite has the same chemical composition1 as pyrite1 and looks like it1 but is lighter colored and usually occurs in fibrous masses4 ,it is the commoner form in limestones and shales1 while pyrite is more likely to occur in igneous and metamorphic rocks4 ,it seems probable that marcasite is due to a more hasty precipitation from cold solutions1 while pyrite is deposited more slowly from hot solutions4 ,isolated crystals of marcasite are rare2 but1 if formed1 they belong to the orthorhombic system4 ,usually some form of twinning is present1 and because of the multiple character of the twinning1 marcasite crystals usually show a ragged outline1 with reentrant angles4 ,it is most abundant in radiated masses1 which appear fibrous on the broken surfaces4 ,it decomposes easily1 taking oxygen from the air and forming1 even in museum cases1 a white efflorescence or 8flower10 which is iron sulphate or melanterite4 ,in moist air it takes water and decomposes to sulphuric acid which may change the surrounding limestone to gypsum4 ,marcasite is found wherever limestones and shales are the country rock4 ,pyrrhotite ,fe,s ,magnetic pyrites ,occurs in masses2 hardness #d2 specific gravity #d4f2 color bronze2 streak grayish-black2 luster metallic2 opaque on thin edges4 ,tabular crystals are known1 but are very rare4 ,they belong to the hexagonal system4 ,this form is easily distinguished from the other yellow minerals by being magnetic4 ,it is by no means as abundant as the two preceding sulphides of iron1 but does occur fairly frequently in veins in igneous rocks1 and less frequently in limestones1 large quantities of sulphuric acid being made from a deposit in limestone at ,ducktown1 ,tenn4 ,it will be found in most states4 ,when associated with nickel it is an important source for the latter mineral1 as at ,sudbury1 ,canada4 ,pyrrhotite is very like a substance found in meteorites1 known as troilite4 ,the ,lead ,group ,after learning how to get iron from the rocks by rude smelting methods1 the early peoples tried heating various rocks1 and some time around #ejj ,b4,c4 stumbled upon lead1 which is rather easily separated from its ores4 ,this metal was used through ,roman times to make pipes1 gutters1 etc4 ,lead is a soft metal1 fairly malleable1 but with little ductility1 and still less tensile strength4 ,though one of the commoner metals1 it does not occur as pure metal in ,nature4 ,it is diffused in minute quantities through the igneous rocks1 and also is found in the sedimentary rocks and in the sea water4 ,its minerals are few1 galena1 the sulphide of lead1 being the commonest1 and at the same time the form in which lead is primarily deposited4 ,galena may also represent a secondary deposition4 ,the other minerals1 cerrusite1 anglesite1 and pyromorphite are results of modification of the galena when it lies near enough to the surface to be acted on by weathering agents1 like water and air4 ,lead minerals are usually associated with zinc minerals1 there being but few places where the minerals of the one group occur without the other4 ,most lead when first smelted from its ore1 contains a greater or less amount of silver in it1 sometimes enough so that the lead ore is better worth working for the silver than for the lead4 ,lead is used in making pipes1 gutters1 bullets1 etc41 and in its oxide forms in the manufacture of paints and glass4 ,eighty-three parts of lead with #ag parts of antimony make type metal4 ,lead and tin alloy to make solder4 ,lead and tin with small amounts of copper1 zinc and antimony make pewter4 ,the ,united ,states produce about #bj of the world's supply of this metal4 ,galena ,pb,s ,pl4 #ag lead glance ,occurs in cubes or cleavable masses2 hardness #b4e2 specific gravity #g4e2 color lead-gray2 streak lead-gray2 luster metallic2 opaque4 ,while there is quite a group of lead-gray minerals1 galena is easily identified by its cleavage1 which is perfect in three directions parallel to the cube faces4 ,even a moderate blow of the hammer will shatter a mass of galena into small cubic pieces4 ,the crystals often have the corners cut by octahedral faces1 and occasionally the edges are beveled by dodecahedral faces4 ,it is not uncommon to find crystals of large size1 several inches across4 ,if galena has #a to #b of bismuth as an impurity1 curiously enough1 the cleavage changes to octahedral1 but this is a rare occurrence4 ,galena may occur as a primary mineral in veins associated with igneous intrusions1 or in irregular masses in metamorphic rocks2 but it is more often found in irregular masses in limestones1 where the limestone has been dissolved1 and the cavities thus formed1 filled with secondary deposits of galena4 ,it also occurs at the contact between igneous rocks and the adjacent rock1 whatever this may be4 ,sometimes it is found in residual clays4 ,among the most important lead deposits are the ,cur d',alene district in ,idaho1 where galena with a high percentage of silver is mined2 the ,leadville1 ,colo41 district where lead1 silver and gold occur together in veins2 the ,joplin1 ,mo41 district1 where lead and zinc ores occur together in irregular masses in limestones2 and the ,wisconsin district of similar character4 ,when found galena is usually associated with sphalerite1 argentite chalcopyrite1 pyrite and calcite4 ,it will be found in every state4 ,cerrusite ,pb,c,o ,pl4 #ah ,white lead ore ,occurs in fibrous or compact masses1 or in orthorhombic crystals1 usually on galena2 hardness #c4e2 specific gravity #f4e2 colorless2 streak white2 luster adamantine2 transparent on thin edges4 ,while the crystals of this mineral simulate hexagonal1 they are actually orthorhombic1 the simple form being an octahedron with two of its edges beveled1 making double six-sided pyramids 7see ,pl4 #ah ,a47 ,usually prism faces are present4 ,twinning is common1 both the simple contact sort1 as shown on ,plate #ah ,b1 and also the sort in which three crystals have grown through each other1 so as to make a six-rayed crystal4 ,the considerable weight1 and the fact that it effervesces in acid serve to identify cerrusite4 ,when pure it is colorless1 but impurities cause it to appear white1 gray or grayish-black1 and sometimes it has a tinge of blue or green4 ,it is likely to occur wherever galena is found1 as a secondary mineral derived from the galena4 ,in this country it is not used as an ore1 for1 as in the ,leadville district1 veins which have cerrusite near the surface change at moderate depths1 and galena takes the place of the cerrusite4 ,it is found all down the ,appalachian ,mountains1 and in all the ,cordilleran ,states4 ,especially fine specimens have come from the ,cur d',alene district in ,idaho4 ,anglesite ,pb,s,o ,pl4 #ah ,occurs in grains and masses1 or in tabular and prismatic orthorhombic crystals2 hardness #c2 specific gravity #f4c2 colorless2 luster adamantine2 transparent on thin edges4 ,two modes of occurrence are characteristic1 one in cavities in galena1 the other in concentric layers around a nucleus of galena4 ,in the former case fine crystals are developed1 in the latter the mineral is in masses4 ,the crystals look like those of barite1 but are soluble in nitric acid while the barite is insoluble4 ,sometimes the crystals are prismatic with pyramidal faces instead of the tabular form4 ,it is found in the lead mines associated with galena1 and in this country is not used as an ore for lead1 but in ,mexico and ,australia it is abundant enough to be mined as an ore4 ,exposed to water which has carbon dioxide in it1 and most surface waters have some1 it readily changes to cerrusite4 ,it is found in ,missouri1 ,wisconsin1 ,kansas1 ,colorado1 and ,mexico4 ,pyromorphite ,pb,cl7,,po7 ,pl4 #ag ,green lead ore ,occurs in small barrel-shaped hexagonal crystals1 and in fibrous or earthly masses2 hardness #c4e2 specific gravity #g2 color green to brown2 luster resinous2 translucent on thin edges4 ,pyromorphite is found in the upper levels of lead mines1 and is formed by the decomposition of galena4 ,its green color 7sometimes shading off toward brown71 considerable weight and resinous luster1 serve to distinguish this mineral4 ,the crystal form is that of a simple hexagonal prism1 with the ends truncated4 ,it is found in ,phnixville1 ,penn41 ,missouri1 ,wisconsin1 ,colorado1 ,new ,mexico1 etc4 ,the ,zinc ,group ,zinc and copper made the brass of early ,roman times2 but even then1 zinc was not known as a separate metal1 the brass being made by smelting rocks in which both zinc and copper occurred1 the zinc never being isolated until much later4 ,some time in the later ,roman times it seems to have been obtained separately1 but then and all down through the ,middle ,ages zinc and bismuth were confused4 ,our earliest record of zinc being smelted1 as we know it today1 was about #agcj in ,england4 ,in those earlier days1 the product1 zinc1 or bismuth1 or both together1 were known as 8spelter10 and this name has clung to zinc in mining and commercial circles2 so that today1 if one looks for quotations in the newspaper1 he often finds zinc under the head of spelter4 ,zinc1 like lead1 is diffused in small quantities through all the igneous rocks4 ,in places it is segregated in fissures or veins leading from the igneous rocks1 along the contact between igneous rocks and either sedimentary or metamorphic rocks1 in limestones where solution cavities have been formed and later filled with zinc minerals1 and as a residue where limestones have been weathered away4 ,in all these places it is closely associated with lead4 ,the sulphide1 sphalerite1 is the primary mineral1 and the other minerals1 like zincite1 smithsonite1 calamine1 willemite1 franklinite1 etc41 are secondary1 resulting from modifications of the original sphalerite4 ,in connection with zinc minerals the region of ,franklin ,furnace1 ,n4 ,j41 is especially interesting1 for at that place are found two large metamorphosed deposits containing a wide range of zinc minerals1 several of which are not found anywhere else4 ,zinc is soft and malleable1 but is only slightly ductile1 and has little tensile strength4 ,it alloys with several metals1 and in this form is most useful today2 three parts of copper to one of zinc making brass2 four or more parts of copper and one of zinc1 making 8gold foil02 copper and zinc 7a little more zinc than copper7 making 8white metal02 three parts of copper to one of zinc and one of nickel making ,german silver2 etc4 ,zinc is also used in large quantities in galvanizing iron1 sheets of iron being dipped into melted zinc and thus thinly coated4 ,it is also used in batteries and a wide range of chemical industries4 ,sphalerite ,zn,s ,pl4 #ai #bj zinc blende1 black jack ,occurs in grains1 in fibrous or layered masses1 or in isometric crystals2 hardness #c4e2 specific gravity #d2 color yellow-brown to almost black2 streak light yellow to brownish2 luster resinous to adamantine2 translucent on thin edges4 ,when in crystals sphalerite occurs most commonly either in dodecahedrons or in tetrahedrons 7hemihedral forms of the isometric octahedron74 ,the cleavage is fairly good and parallel to the faces of the dodecahedron4 ,the difficulty usually is to get large enough crystalline masses to see this cleavage clearly1 but by examining the angles between the faces of cleavage pieces they will be found to be the same as those on a dodecahedron4 ,when the mineral is pure1 it has the color of resin1 but sometimes it is reddish to red-brown1 and then it is called 8ruby zinc10 more often it is dark brown due to the presence of iron as an impurity4 ,this is what the miners call 8black-jack40 ,the presence of iron also tends to make the streak darker4 ,the hardness1 streak and cleavage will usually determine this mineral readily4 ,sphalerite is the primary ore of zinc and is usually found in fissures and veins leading from masses of igneous rocks1 or along the surface of contact where igneous rocks like granite or lavas come against such metamorphic rocks as gneisses1 schists1 or crystalline limestones4 ,in the region of ,joplin1 ,mo41 however1 the sphalerite is of secondary character1 having been gathered by waters circulating through the limestones1 and deposited in them in irregular pockets4 ,this ,joplin district has produced more zinc than any other in the world4 ,the ,united ,states annually produces about #be of the world's supply of this metal4 ,sphalerite is always associated with galena1 and such other minerals as argentite1 pyrite1 chalcopyrite1 fluorite1 quartz1 calcite and barite1 are very apt to be present4 ,it will be found in almost every state1 especially in fissures and veins1 and less frequently in cavities in limestones4 ,zincite ,zn,o ,pl4 #ai #bj red zinc ore ,usually occurs massive1 but may be found in crystals2 hardness #d2 specific gravity #e4f2 color deep red2 streak orange2 luster subadamantine2 translucent on thin edges4 ,when in crystals zincite forms in hexagonal prisms with hexagonal pyramids on the ends4 ,this is rather rare1 most of the zincite being found in massive form4 ,the cleavage is parallel to the prism faces and perfect4 ,the deep red color and orange streak are wholly characteristic4 ,this mineral is so common at ,franklin ,furnace1 ,n4 ,j41 as to be an important ore1 but it is very seldom found elsewhere4 ,this district1 as mentioned before1 is a peculiar one for zinc minerals4 ,the zinc beds are in a metamorphosed limestone1 and into this are intruded numerous dikes of granite4 ,probably the zinc was originally present in the bed of limestone as smithsonite1 calamine and other secondary minerals of zinc4 ,when intruded by the hot granite the smithsonite 7carbonate7 may well have been altered to the oxide1 zincite2 while the calamine 7hydrous silicate7 became the simple silicate1 willemite4 ,willemite ,zn,si,o ,pl4 #bj ,occurs in masses or in crystals2 hardness #e4e2 specific gravity #d4a2 color pale yellow when pure2 luster resinous2 translucent on thin edges4 ,willemite is another of the minerals which are distinctively characteristic of ,franklin ,furnace1 and found elsewhere very rarely4 ,it is so common there as to be one of the principal ores1 and mostly occurs in irregular masses1 but is also found in crystals4 ,these are hexagonal prisms1 with a three-sided 7rhombohedral7 pyramid on the ends4 ,the color when pure is whitish or greenish-yellow1 but with small amounts of impurities it may be flesh-red1 grayish-white or yellowish-brown4 ,when in crystals it is easily determined2 but when massive it looks like calamine1 and can only be distinguished by placing a bit of the mineral in a closed tube and heating it1 in which case calamine will give off water vapor1 while willemite will not4 ,this mineral is one of those resulting from metamorphic alteration and is derived from calamine1 when the latter loses its water of crystallization4 ,it is common at ,franklin ,furnace1 ,n4 ,j41 and also found occasionally elsewhere1 as at ,salida1 ,colo41 and in ,socorro ,co41 ,new ,mexico4 ,calamine ,zn7,,oh7,si,o ,occurs as crystalline linings in cavities1 or as botryoidal or stalactitic masses2 hardness #e2 specific gravity #c4d2 colorless to white2 luster vitreous4 ,calamine resembles both smithsonite and willemite when in non-crystalline masses4 ,from the smithsonite it is easily separated by the fact that in nitric acid the smithsonite effervesces and the calamine does not4 ,from willemite it is harder to distinguish1 but a piece may be placed in a closed tube and heated4 ,if it is calamine water vapor will be given off1 if willemite nothing happens4 ,when calamine occurs in crystals these are orthorhombic and mostly tabular1 and the crystals are peculiar in that the two ends are terminated differently4 ,both this and smithsonite are secondary minerals and usually occur together when zinc is found in limestones4 ,it is abundant at ,franklin ,furnace and ,sterling ,hill1 ,n4 ,j41 and also found at ,phnixville1 ,penn41 in ,wythe ,co41 ,va41 and ,granby1 ,mo4 ,smithsonite ,zn,c,o ,pl4 #ba ,dry bone ,usually occurs as incrustations1 grains1 earthy or compact masses1 and as crystals2 hardness #e2 specific gravity #d4d2 color white1 yellow1 greenish or bluish2 streak white2 luster vitreous2 transparent on thin edges4 ,when pure this mineral is colorless1 but1 as it occurs1 it is usually white1 or tinged with some shade of yellow1 green1 or blue1 but in all cases its streak is white4 ,the crystals are rhombohedrons often with edges beveled or corners cut by other faces4 ,it resembles calamine and willemite1 but is readily separated from either of these by the acid test1 for smithsonite effervesces when acid is placed on it4 ,next to sphalerite1 smithsonite is the commonest of the zinc minerals4 ,it is a secondary mineral1 resulting from the action of lime-charged water acting on sphalerite1 and so is likely to be found wherever zinc minerals occur in a limestone region4 ,in the ,wisconsin-,illinois-,iowa district it serves as a minor ore of zinc1 and is termed here 8dry bone40 ,it is also found in the ,missouri and ,arkansas districts1 and in ,europe is an important ore for zinc4 ,franklinite 7,zn,mn7,fe,o ,pl4 #ba ,occurs in compact grains or masses1 and in isometric octahedrons2 hardness #f2 specific gravity #e2 color black2 streak reddish-brown2 luster metallic2 opaque on thin edges4 ,this is a mineral peculiar to the ,franklin ,furnace region1 from which it gets its name4 ,it looks like magnetite1 but its reddish-brown streak and lack of magnetism distinguish it4 ,when it occurs in octahedrons1 the edges are rounded1 while those of magnetite are sharp4 ,it is a complex and variable oxide of zinc1 iron and manganese1 which has resulted from the metamorphism of the beds in which it occurred probably being originally something quite different4 ,the ,manganese ,group ,though manganese was known in the mineral pyrolusite in early times1 it was then thought to be magnetite or magnetic iron ore4 ,it was not until #aggd that it was isolated and recognized as a distinct element4 ,manganese is one of the lesser elements in the crust of the earth1 making less than 4#jg of one percent1 but as an alloy with other metals1 especially iron1 it has attained a considerable importance to man4 ,it is used chiefly with iron1 #bj of manganese making the alloy1 spiegeleisen1 a combination which occurs in ,nature in ,germany1 and from #bj to #hj making ferromanganese4 ,these alloys are in great demand because they make an especially tough steel essential in the manufacture of munitions4 ,the sources for manganese are the oxide ores1 manganite1 pyrolusite and psilomelane1 which have been formed as secondary minerals1 as a result of the weathering of silicates which carry manganese4 ,they occur widely enough1 but throughout the ,united ,states the deposits are small1 and this is one of the elements in which this country is not self-sufficient4 ,the largest producer of manganese is ,russia2 however she consumes almost all of her output at home1 and our supply comes from the next largest producers1 ,india1 the ,union of ,south ,africa1 and the ,gold ,coast4 ,a shift in trade may be expected when ,brazil's recently discovered ore body in ,matto ,grosso is brought into full production4 ,besides being used as an alloy1 manganese is employed in making paints and dyes1 for clearing glass1 and for some types of electric batteries4 ,pyrolusite ,mn,o ,occurs in earthy or fibrous masses2 hardness #a-b2 specific gravity #d4h2 color black2 streak black2 luster dull2 opaque4 ,pyrolusite occurs in soft masses and incrustations1 usually leaving a sooty mark on the fingers4 ,sometimes it seems to be in crystals1 but these are pseudomorphs which have the form of manganite1 from which the pyrolusite has formed as a result of the water having been driven from the manganite4 ,frequently pyromorphite and manganite will be found together1 and in some cases the outer part of a mass or crystal will be pyrolusite1 while the center is still manganite4 ,psilomelane is another oxide of manganese with water and may appear very like pyrolusite1 but both manganite and psilomelane have much greater hardness than does pyrolusite4 ,if there is difficulty in deciding about pyrolusite1 it may be placed in a closed tube and heated4 ,it will not be affected by the heat1 while1 under the same circumstances1 both manganite and psilomelane will give off water vapor4 ,pyrolusite usually occurs in black streaks or pockets in residual clays which have formed as a result of the decomposition of limestones4 ,it may also occur in dendritic forms in seams and crevices 7see manganite74 ,it is found in ,vermont1 ,massachusetts1 ,virginia1 ,arkansas1 ,colorado1 ,california1 etc4 ,psilomelane ,mn,o,h,o ,occurs in compact botryoidal or stalactitic masses2 hardness #e-f2 specific gravity #d4b2 color black2 streak brownish-black2 luster metallic2 opaque on thin edges4 ,psilomelane is very like pyrolusite1 and often occurs with it4 ,it is distinguished by its greater hardness1 and the fact1 that when heated in a closed tube1 it gives off water vapor4 ,from manganite it is more easily distinguished1 for it never occurs in crystals1 while the manganite is usually crystalline4 ,this and pyrolusite are the principal ores of manganese4 ,wad is an impure form of psilomelane1 having some iron oxide mixed with the manganese oxide1 usually limonite2 or the impurity may take the form of a copper1 cobalt1 lithium or barium oxide4 ,psilomelane is found at ,brandon1 ,vt41 in ,arkansas1 ,colorado1 ,california1 etc4 ,manganite ,mn,o,h,o ,pl4 #bb ,occurs in prismatic crystals1 or in columnar or fibrous masses2 hardness #d2 specific gravity #d4d2 color steel gray2 streak reddish-black2 luster submetallic2 opaque on thin edges4 ,this is the form taken by manganese oxide when it crystallizes in the presence of moisture1 and pyrolusite frequently changes to manganite when exposed to moisture4 ,the crystals are orthorhombic prisms1 with striated sides and the ends truncated4 ,these prisms usually occur in bundles and give the mineral a fibrous appearance4 ,manganite is not hard to identify1 the striations on the crystals and the streak being very characteristic4 ,in seams and tiny crevices this mineral1 and often pyrolusite1 grows in a branching manner1 resembling tree-like or 8mossy0 masses4 ,this is termed dendritic1 and the growths of manganese minerals are called dendrites4 ,one of the most curious of these is when the 8mossy0 growth is inclosed in chalcedony1 making the so-called moss agate4 ,these moss agates are abundant through the ,rocky ,mountains and are frequently cut for semi-precious stones4 ,the finest ones however come from ,india and ,china4 ,manganite is found in the ,lake ,superior region1 ,colorado1 etc4 ,rhodochrosite ,mn,c,o ,occurs in compact cleavable masses2 hardness #d2 specific gravity #c4e2 color rose to dark red2 streak white2 luster vitreous2 translucent on thin edges4 ,this usually occurs in pink to red masses which cleave readily parallel to the faces of the rhombohedron4 ,when it is found in crystals1 which are rare1 these too are rhombohedrons4 ,it is usually found in veins as a gangue mineral with copper1 silver or zinc ores4 ,its beautiful color and the fact that it effervesces in acid serve to distinguish this mineral4 ,it is found at ,branchville1 ,conn41 at ,franklin ,furnace1 ,n4 ,j41 and in veins with silver in ,colorado1 ,nevada1 and ,montana4 ,the ,aluminum ,group ,though aluminum is one of the most abundant of all the metals1 making some #h of the crust of the earth1 its union with other elements is so firm1 that only recently have methods been found for getting the metal free4 ,it was first isolated in #ahdf1 but up to #ahij the extraction of aluminum was so expensive1 that it could not be widely used4 ,about that time electrical processes were applied to its extraction1 and since then the price has steadily dropped1 until now it is under 4#bj per pound4 ,it is very malleable1 and ductile1 and has high tensile strength4 ,exposed to the air1 water or ordinary gases1 it does not tarnish2 and it is very light1 an equal bulk weighing about a third as much as iron4 ,the combination of lightness and strength1 and the fact that it is a good conductor of electricity1 have made it available for a wide range of uses1 such as electrical apparatus1 delicate instruments1 boats1 aeroplanes1 and domestic utensils4 ,it is an essential component of all the important rocks1 except sandstone and limestone1 and combines to a greater or less degree in a host of minerals4 ,though present in clays1 shales1 argillites1 feldspars1 and micas1 it is only from bauxite that it has been successfully extracted4 ,aside from the small number of simple compounds of aluminum grouped here1 it also takes a part in the make-up of a large series of minerals termed silicates1 treated a little further on in this book4 ,it alloys with other metals1 especially copper4 ,the union of copper and a small amount of aluminum makes aluminum-bronze1 which looks like gold and is used for watch chains1 pencil-cases1 etc41 and also for the antifriction bearings of heavy machinery4 ,a small amount added to steel prevents air holes and cracks in casting4 ,corundum ,al,o ,pl4 #bc ,occurs in cleavable masses or in hexagonal crystals2 hardness #i2 specific gravity #d2 colorless1 red1 yellow1 blue1 or gray2 luster vitreous to adamantine2 translucent to transparent on thin edges4 ,corundum is readily recognized by its hardness1 second only to that of the diamond4 ,the crystals may be simple six-sided prisms1 hexagonal pyramids or combinations of the two4 ,the cleavage is usually described as parting1 for it is by no means perfect1 but when it is recognizable it is parallel to the faces of a rhombohedron1 and cleavage pieces may appear almost cubic4 ,when in clear and perfect crystals this mineral is one of the most highly prized of all the gems4 ,clear and colorless it is known as the 8,oriental white sapphire02 when tinged with blue it is the sapphire2 when colored yellow1 the 8,oriental topaz02 when green1 the 8,oriental emerald02 when purple1 the 8,oriental amethyst0 and when red1 the ruby4 ,sapphires range from colorless to deep blue1 the value depending on the shade of the blue1 and increasing as the color deepens4 ,the ,oriental topaz can easily be confused with the true topaz1 which is a much commoner and less valuable gem1 but can be distinguished by the hardness1 topaz having a hardness of but #h4 ,the name emerald is applied to several green gems1 mostly to beryl1 which is not so hard and is the true emerald4 ,the ,oriental emeralds have a value about the same as diamonds4 ,rubies of clear and deep color are the rarest of all gems1 ranging in value about three times as high as diamonds of equal size4 ,the most sought-for shade is the so-called 8pigeon-blood red10 and the value of a stone of this sort is almost dependent on the whim of the buyer4 ,the best of the rubies come from granites or metamorphosed limestones in ,burma2 the best sapphires from ,ceylon1 though both of these1 and some of the other corundums of gem quality1 have been found in ,north ,carolina and ,montana4 ,around these stones1 which have been used so long among the ,hindus1 ,persians1 ,jews1 ,egyptians1 and ,christians1 a wealth of lore has been woven4 ,the sapphire was ,saturn's stone1 and a talisman to attract ,divine favor4 ,where tradition makes the stone on which the ten commandments were written the sapphire1 it is probable that1 what was really meant1 is lapis lazuli1 as is also the case when sapphires are mentioned as building stones for the celestial gates4 ,the ruby in ancient lore is termed 8lord of stones10 8gem of gems0 etc41 and so protected its wearer that he was safe from injury in peace or war4 ,when corundum is colored brown by impurities of iron1 it is termed corundum1 when black by greater quantities of iron1 it is emery4 ,these varieties are far the commonest form in which corundum occurs1 and when ground to finer or coarser powder make the commercial emery4 ,emery is likely to be found in sands1 making so-called 8black sands10 where it has accumulated as a result of the weathering to bits corundum-bearing rocks4 ,in some one of its forms1 corundum is found in ,massachusetts1 ,connecticut1 ,new ,york1 ,new ,jersey1 and all down the ,appalachian ,mountains1 also in ,colorado1 ,montana1 ,california1 etc4 ,bauxite ,al,o#b;,h,o ,occurs in grains1 or oolitic or clay-like masses2 hardness #a-c2 specific gravity #b4e2 color white to yellowish-white or reddish-brown4 ,bauxite never comes in crystals1 but is usually in earthy masses1 which have resulted from the decomposition of granitic or volcanic rocks1 in circumstances where hot alkaline waters were present4 ,this explanation seems to apply especially to the deposits in ,france1 which were first the chief source of the bauxite1 and may be applicable to those in ,georgia and ,alabama4 ,some of the other deposits1 however1 do not seem to have had any hot water available1 and the deposit appears more like simple decomposition of the underlying rocks by alkaline waters4 ,in many cases bauxite resembles limonite in being a mixture of two or more aluminum oxides with water of crystallization1 such as ,al,o,h,o1 ,al,o#b;,h,o and ,al,o#c;,h,o4 ,this is particularly true of the bauxite which resulted from the decomposition of rocks by surface water4 ,bauxite is the ore from which aluminum is obtained4 ,the deposits are not large1 but the ,united ,states has its share of them4 ,it is found in ,alabama1 ,arkansas1 ,georgia1 ,missouri1 ,tennessee1 and ,california4 ,cryolite ,na,al,f ,ice stone ,occurs in pseudo-cubic crystals or massive2 hardness #b4e2 specific gravity #c2 color white2 luster vitreous2 transparent on thin edges4 ,cryolite is a relatively soft mineral1 colorless to white as snow2 for which reason1 and partly also because it comes mostly from ,greenland it is called 8ice stone40 ,it is really monoclinic but the inclination of the c axis is so slight1 that1 unless examined carefully1 the crystals appear to be cubic4 ,until about #aijj great quantities of this mineral were shipped from ,west ,greenland1 and from them the metal aluminum was extracted4 ,when bauxite was discovered1 it was found to be considerably cheaper to make the aluminum from that mineral1 and now cryolite is no longer sought4 ,aside from its occurrence in ,greenland some cryolite is found in ,colorado1 near ,pike's ,peak4 ,the ,arsenic ,group ,the metal1 arsenic1 is a dark steel gray in color1 when the surface is fresh1 but it soon tarnishes4 ,it is very brittle and easily powdered under the hammer1 and its only use as a metal1 is for an alloy with lead in making shot4 ,its compounds find a wider use4 ,the white powder called 8arsenic0 is arsenous acid1 and is used mostly in making poisons1 which fortunately are easily detected in animal tissues4 ,copper arsenate1 7,scheele's green7 is a pigment used in making green paint1 and formerly in the green colors of wall paper4 ,a combination of arsenous acid1 copper oxide and acetic acid is the well known ,paris ,green1 so much used for an insecticide4 ,beside these uses1 arsenic serves a large number of other purposes1 as in making glass and enamel1 embalming fluids1 and various medicines4 ,curiously arsenic plays a double part1 acting part of the time as a metal1 as in the two following minerals1 and part of the time as a non-metal1 as in cobaltite1 niccolite1 etc4 ,arsenopyrite ,fe,as,s ,pl4 #bd ,occurs in well formed crystals1 grains1 or masses2 hardness #e4e2 specific gravity #f2 color silver-white2 streak black2 luster metallic2 opaque on thin edges4 ,when in crystals1 they are usually short prisms of the orthorhombic system1 either end being terminated with a low roof4 ,though usually described as silver-white in color1 there is always a brassy cast to the color4 ,its appearance is much like cobaltite and smaltite1 but it can be easily distinguished from both these by putting a piece in nitric acid4 ,the arsenopyrite will not materially change the color of the fluid1 but the other two turn it rose-red1 and all give off the smell of sulphur4 ,it looks sometimes like marcasite1 but that is yellower1 and has the fibrous structure1 not found in arsenopyrite4 ,it is found in veins or in metamorphic rocks1 associated with argentite1 galena1 sphalerite1 chalcopyrite and pyrite4 ,it is distinctly a mineral formed by deposition from hot vapors or hot water rising from either lavas1 or in the course of metamorphism4 ,it is found in ,new ,hampshire1 ,vermont1 ,massachusetts1 ,connecticut1 ,new ,york1 ,new ,jersey1 ,california1 etc4 ,realgar ,as,s ,pl4 #bd ,occurs in incrustations or scattered grains2 hardness #a4e to #b2 specific gravity #c4e2 color orange2 streak orange2 luster resinous2 opaque on thin edges4 ,crystals are very rare1 but when found are short monoclinic prisms4 ,the color is aurora-red1 changing to orange as soon as it is exposed to the air4 ,this and the streak are entirely characteristic4 ,it is a mineral associated with hot vapors or hot waters1 and is found about volcanoes1 as deposits from the hot water of the geysers in ,norris ,basin1 ,yellowstone ,park1 and in veins1 associated with barite1 stibnite1 quartz1 etc41 as in ,massachusetts1 ,utah1 ,california1 etc4 ,orpiment ,as,s ,occurs as incrustations or powdery masses2 hardness #a to #b2 specific gravity #c4e2 color lemon yellow2 streak yellow2 luster resinous4 ,this mineral is very like realgar in its physical properties1 and likely to occur with it4 ,it gives the lemon yellow color to the basins about hot springs1 as in the ,yellowstone ,park1 and about volcanoes4 ,it also comes in veins with realgar4 ,molybdenum ,molybdenum is a rare metal1 silvery-white in color1 brittle and very difficult to fuse4 ,it is used mostly as an alloy of steel1 to make certain grades of tool steel4 ,the world's greatest supply is obtained from ,climax1 ,colorado1 where the principal ore mineral is molybdenite4 ,molybdenite ,mo,s ,occurs in scales or scaly masses1 occasionally in tabular hexagonal crystals2 hardness #a4e2 specific gravity #d4g2 color lead-gray2 streak bluish-gray2 luster metallic2 opaque4 ,this mineral is the chief source for the metal molybdenum4 ,its extreme softness and greasy feel will distinguish it at once from any other mineral except graphite1 which has much the same qualities1 but its scaly character and the more bluish tinge in streak and color will distinguish these two4 ,it occurs in granites1 gneisses1 and metamorphic rocks in ,colorado1 ,new ,mexico1 ,maine1 ,connecticut1 ,new ,hampshire1 ,new ,york1 ,pennsylvania1 etc4 ,antimony ,antimony is another hard1 brittle metal1 of bluish-white color4 ,exposed to the air at ordinary temperatures it does not tarnish2 and this combined with its hardness make it useful for such alloys as ,britannia metal1 type metal1 and pewter4 ,only one of its minerals1 stibnite1 is common enough for mention4 ,stibnite ,sb,s ,pl4 #be gray antimony ,occurs in prismatic or needle-like crystals2 hardness #b2 specific gravity #d4e2 color lead-gray2 streak lead-gray2 luster metallic2 opaque4 ,the crystals of stibnite are orthorhombic and usually elongated1 the sides striated and the ends with low pyramids on them4 ,sometimes the long crystals are curved or even twisted4 ,there is a well-developed cleavage parallel to face b in the figure4 ,while the color is similar to that of galena1 the form and cleavage are so different that stibnite is easily determined4 ,the ancients used stibnite to color their eyebrows1 now it is the source for the metal antimony4 ,hungary and ,japan are famous for the fine large crystals they produce2 but moderate sized crystals may be found in this country4 ,it occurs in veins along with pyrite1 galena1 cinnabar1 and realgar1 with quartz1 calcite or barite as gangue minerals4 ,stibnite has been found in ,arkansas1 ,california1 ,nevada1 and ,utah4 ,the ,nickel ,group ,nickel as a metal is silvery-white in color1 rather hard1 and does not tarnish when exposed to the air4 ,when pure it is malleable and fairly ductile4 ,it is highly useful for plating other metals to protect their surfaces4 ,alloyed with steel1 it makes a product of extreme hardness4 ,copper1 zinc1 and nickel make the well known ,german silver4 ,nickel has a fairly large range of minerals1 but they do not occur with any abundance in the ,united ,states1 so that we have to import most all of our nickel4 ,in the earlier days ,new ,caledonia produced most of the world's supply1 but recently since the finding of large nickel deposits near ,sudbury1 ,canada1 this locality has not only outstripped ,new ,caledonia1 but now produces four-fifths of the world's supply4 ,in this country but two nickel minerals will be found at all common4 ,niccolite ,ni,as ,pl4 #be copper nickel ,occurs in masses2 hardness #e4e2 specific gravity #g4d2 color pale coppery-yellow2 streak pale brownish-black2 luster metallic2 opaque on thin edges4 ,niccolite is very seldom in crystals1 but if they do occur they are hexagonal4 ,the mineral looks a little like smaltite1 but in case there is any question of the determination1 dissolve a piece in nitric acid1 and if niccolite1 it will color the solution green4 ,niccolite is usually associated with copper and silver ores1 and in this country has been found at ,chatham1 ,conn41 and ,silver ,cliff1 ,colo4 ,it may be associated with pentlandite1 a sulphide of iron and nickel1 which is similar in appearance1 but not so hard1 and occurs in small grains throughout dark lavas4 ,the particles of pentlandite are however so small1 that they are seldom noticeable1 but at ,sudbury1 ,canada1 this is the chief ore of nickel4 ,millerite ,ni,s capillary pyrites ,occurs in needle-like or fibrous crystals2 hardness #c4e2 specific gravity #e4e2 color brass-yellow2 streak greenish black2 luster metallic2 opaque on thin edges4 ,the fibrous crystals of millerite belong to the orthorhombic system4 ,the color and streak suggest pyrite1 but the crystals are long and slender1 while pyrite is in cubes1 octahedrons1 etc4 ,if there is any doubt of the identity of this form1 place a piece in nitric acid1 and if it is millerite1 it will color the acid green4 ,it may occur in veins associated with cobalt and silver minerals1 or as a secondary mineral as at ,gap ,mine1 ,penn41 or in cavities in sedimentary rocks4 ,in the last case it usually is in needle-like crystals growing through calcite crystals1 as at ,st4 ,louis1 ,mo41 ,keokuk1 ,iowa1 and ,antwerp1 ,n4 ,y4 ,the ,cobalt ,group ,as a metal1 cobalt is hard1 brittle1 and of a grayish color1 tinged with red4 ,it was not recognized as a separate element until #agce1 and even today is one of the minor metals4 ,cobalt1 chromium and a little tungsten make the alloy stellite1 which has come into large use in making high-speed tools4 ,the oxide of cobalt 7,co,o7 is 8smalt10 used to give the blue color to porcelain1 pottery1 glass1 tiles1 etc4 ,invisible ink is made by diluting cobalt chloride in a large quantity of water4 ,this solution is a faint pink color and practically invisible on paper1 but if heated it loses water and turns blue in color1 and is perfectly visible4 ,cobalt is another of the metals1 of which the ,united ,states does not have an adequate supply4 ,sweden1 ,norway and ,india were the chief sources of supply until cobalt was found near the town of ,cobalt in ,ontario1 ,canada1 and now this district furnishes #ij of the world's supply4 ,cobaltite ,co,as,s ,pl4 #bf cobalt glance ,usually crystalline in cubes1 pyritohedrons or octahedrons2 hardness #e4e2 specific gravity #f4a2 color reddish silver-white2 streak grayish-black2 luster metallic2 opaque on thin edges4 ,in color cobaltite may appear very like arsenopyrite1 especially if the reddish tinge is not strong1 in which case the mineral can be definitely determined by putting a piece in nitric acid4 ,if it is cobaltite the solution will be colored rose-red1 if arsenopyrite there will be no change of color4 ,the forms of the crystals are the same as those of pyrite1 but the color will easily distinguish cobaltite from pyrite4 ,this pink color is characteristically present either in or about cobalt minerals1 being sometimes called 8cobalt bloom40 ,it is a cobalt-arsenic-oxide with water of crystallization 7,co,as,o#h;,h,o71 which results from the exposure of cobalt and arsenic minerals to air and moisture4 ,it is the pink color on the figures of both cobaltite and smaltite4 ,in ,sweden1 ,norway and ,india1 this is the chief ore for cobalt1 but in the ,united ,states it is rather rare1 but is found in ,oregon1 and at ,cobalt1 ,canada4 ,smaltite 7,co,ni7,as ,pl4 #bf gray cobalt ore ,usually occurs in masses2 hardness #e4e2 specific gravity #f4b2 color tin-white to steel-gray2 streak grayish-black2 luster metallic2 opaque on thin edges4 ,while very like cobaltite1 smaltite is almost never found in crystals1 but when crystals are found1 they are cubes4 ,the color is tin-white but there is usually a pink tinge visible due to the presence of small amounts of 8cobalt bloom40 ,if in any doubt about the determination of this mineral1 put a piece in nitric acid4 ,if it colors the acid rose-pink1 and is non-crystalline it is pretty surely smaltite2 if the acid is not affected it is arsenopyrite4 ,smaltite is found in ,kentucky1 ,missouri1 ,colorado1 ,idaho1 ,california1 and at ,cobalt in ,canada4 ,chromium ,this metal gets its name in recognition of the many colors 7chroma 8color071 in which its compounds appear4 ,chromic oxide is a vivid green1 used to color porcelains1 pottery1 tiles1 etc41 and also as a substitute for the arsenical greens formerly used in wall-paper4 ,the chromate of lead is the pigment1 well known to artists as 8chrome yellow10 and the bichromate of potassium is bright red4 ,the metal is obtained in at least two different forms2 one hard1 brittle and so resistant to heat as to be infusible at temperatures which would volatilize platinum2 the other as a powder which burns brightly if heated in air4 ,while used in paints1 dyes1 etc41 its greatest importance is for the making of ferro-chrome steel1 which is used where resistance to sudden shock is required1 as in armor plate1 automobile springs1 ball bearings1 etc4 ,with tungsten and cobalt it makes the alloy1 stellite1 as noted above4 ,chromium was used in relatively small quantities before the first world war1 and we imported our supplies from ,turkey1 ,india1 ,new ,caledonia1 and ,rhodesia4 ,during the last war we started a large-scale development of low-grade ores in ,montana1 and can now supply all of our needs from this source4 ,chromite ,fe,cr,o chromic iron ,occurs in grains1 masses1 or isometric octahedrons2 hardness #e4e2 specific gravity #d4d2 color black2 streak dark-brown2 luster submetallic2 opaque on thin edges4 ,in form1 color and streak chromite resembles magnetite and franklinite4 ,from the magnetite it is distinguished by being non-magnetic2 from the franklinite1 by being insoluble in hydrochloric acid1 while the franklinite is soluble4 ,chromite furnishes practically all the chromium used in the arts and manufactures4 ,it is a mineral associated with high temperatures1 and therefore found in dark lavas1 serpentine1 and olivine4 ,it occurs in ,pennsylvania1 ,maryland1 ,new ,jersey1 ,montana1 ,oregon1 ,wyoming1 and ,california4 ,tungsten ,this element is obtained either as a heavy dark-gray metal1 which is very hard and difficult to fuse1 or as a dark-gray powder4 ,it is used as an alloy with iron1 one part of tungsten to nine of steel1 to make the ferrotungsten1 which has extraordinary hardness1 and is used mostly for high-speed tools4 ,tungsten is also one of the three metals 7cobalt1 chromium and tungsten7 which are alloyed together to make stellite4 ,some of the tungsten supply is also used to make the films in incandescent lamps1 and in some of the chemical industries4 ,it has but one important ore1 wolframite1 and this is found in the ,united ,states in but small quantities2 so that we ordinarily have to import the greater part of what we use4 ,during the last war1 under the stimulus of high prices and the urge of necessity1 we did find and produce substantial quantities of tungsten4 ,china is the world's largest producer of tungsten ore with ,burma second1 and the ,united ,states a poor third4 ,wolframite 7,fe,mn7,,wo ,occurs in monoclinic crystals or in crystalline masses2 hardness #e4e2 specific gravity #g4d2 color dark-brown to black2 streak nearly black2 luster submetallic2 opaque on thin edges4 ,if in crystals the form will serve to distinguish this mineral from cassiterite and ilmenite1 the two which it most resembles2 but if it is massive the only sure way to decide is to put a piece in strong sulphuric acid2 if it dissolves and throws down a yellow precipitate 7tungstic acid7 it is wolframite4 ,like the two other minerals mentioned above it occurs in veins in igneous rocks1 being associated with high temperatures4 ,as it is almost insoluble in water1 like cassiterite and ilmenite1 it is likely to occur with them in the sands which are the result of the disintegration of the rocks which carried the minerals2 and so a large part of the supply today comes from placer deposits4 ,it is found in ,connecticut1 ,north ,carolina1 ,missouri1 ,colorado1 and ,california4 ,radium1 ,uranium and ,vanadium ,these three metals are all rare and occur together4 ,radium1 discovered in #ahih1 is a heavy metal which has proved very useful because of its radio-activity1 that is1 its power of giving off or radiating tiny particles of matter known as ,x-rays1 part of which are charged with positive electricity1 and part of them with negative electricity4 ,the ability of these rays to pass through other substances has made possible photographing the denser substances within those less dense1 as the bones within the flesh1 or metal within leather or wood1 etc4 ,the rays have proved of great value medicinally1 and are also used to make objects luminous in the dark4 ,these ,x-rays are also used in the study of the ultimate structure of matter1 as it can be thus obtained in such small units4 ,uranium is another element which is radio-active and can be used for many of the same purposes as radium4 ,vanadium1 the third of these associated metals1 and the commonest of the group1 is not radio-active4 ,it is a silvery-white metal1 mostly used as an alloy with steel to give it great hardness4 ,carnotite ,k,o#b,u,o,v,o#c;,h,o ,pl4 #bg ,occurs in earthy masses2 color yellow4 ,this mineral is included here1 not because it is common1 but because it is of such great interest4 ,it is the chief source of supply in the ,united ,states of radium1 uranium and vanadium4 ,it is a lemon-yellow earth or powder1 which looks a little like orpiment4 ,it is however found in a sandstone1 instead of where hot waters have deposed minerals4 ,from a ton of this ore about #aj pounds of uranium oxide1 #ee pounds of vanadium and _/th of a gram of radium are obtained4 ,carnotite is found in south-west ,colorado and south-east ,utah1 and on ,carrizo ,mountain on the line between ,arizona and ,new ,mexico4 ,mercury ,mercury1 or quicksilver1 is the only metal which is liquid at ordinary temperatures4 ,it is silvery-white in color1 with a striking metallic luster1 and at the low temperature of #ffb ,f41 boils and changes to a colorless vapor4 ,mercury alloys with certain metals1 these alloys being known as amalgams4 ,in this way it is especially useful for the recovery of gold and silver1 the mercury being added to crushed ore1 the gold or silver uniting with the mercury in a liquid amalgam1 which is then drawn off and heated to a temperature above #ffb ,f41 at which temperature the mercury volatilizes and is recovered1 while the gold or silver remains behind4 ,mercury also forms a solid amalgam with tin which is used to coat glass1 the high metallic luster making the most effective looking glass4 ,it is also used in medicines 7calomel1 corrosive sublimate1 etc471 for scientific instruments 7thermometers1 barometers1 etc471 in cosmetics1 in paints for ship bottoms1 etc4 ,though there are some #be minerals of mercury1 only one is common or important as a source of the metal1 cinnabar4 ,the ,united ,states is self-sufficient as far as mercury is concerned1 producing just about as much as it uses4 ,the leading producers are ,spain1 ,austria1 ,italy1 and the ,united ,states4 ,commercially mercury is quoted as quicksilver1 and in flasks of #ge pounds each4 ,cinnabar ,hg,s ,pl4 #bg ,occurs in massive or earthy form1 or in minute crystals in cavities2 hardness #b4e2 specific gravity #h2 color scarlet to dark red2 streak vermilion2 luster adamantine2 translucent on thin edges4 ,the bright-red color and the streak are usually enough to identify this mineral at once1 but some of the darker varieties resemble hematite or zincite in appearance1 but both these have much greater hardness4 ,when in crystals they are tiny hexagonal prisms with pyramids on the end4 ,cinnabar is usually found in or near metamorphic or igneous rocks1 either in veins leading from the igneous rocks1 or in metamorphic rocks1 or it may occur disseminated through metamorphic rocks4 ,it is associated with quartz or calcite1 and may occur with other sulphides like pyrite1 galena1 argentite1 etc4 ,it is most abundant in ,california1 but is also found in ,oregon1 ,washington1 ,idaho1 ,arizona1 ,nevada1 ,utah1 ,texas1 and ,montana4 ,tin ,tin has been known since early ,roman times1 and the mines at ,cornwall1 ,england1 were worked from that time all through down to the present1 but now they are becoming of minor importance as they approach exhaustion4 ,the metal is silvery-white1 does not easily tarnish1 is malleable1 but has little ductility and little tensile strength4 ,tin is mostly used in making tin plate1 a thin sheet of steel covered with tin1 the tin being only #a to #b of the total weight4 ,this tin plate is mostly made into tin cans1 and used as containers for food4 ,some tin is used in making solder1 tin-foil1 tubes for paste1 vaseline1 etc41 and around #ajjj tons per year for weighting silk4 ,this 8weighting0 makes the silk heavier by about #be and gives it a 8rustle10 which1 while much in evidence1 is really indicative that the silk is not pure4 ,the ,united ,states produces very little tin1 most of the world's supply coming from the ,malay ,peninsula1 ,dutch ,east ,indies1 ,china1 and ,bolivia1 with small amounts from several other countries4 ,cassiterite ,sn,o ,pl4 #bh tin stone ,occurs in tetragonal crystals1 massive1 or in grains and pebbles2 hardness #f4e2 specific gravity #g2 color black or dark-brown2 streak gray2 luster adamantine2 translucent on thin edges4 ,the crystals are short prisms with pyramidal ends4 ,twinning is common4 ,cassiterite also occurs in fibrous masses1 and when it is weathered from its original location1 is so insoluble and hard1 that it remains as grains and pebbles1 making placer-deposits1 from which today three quarters of the supply is obtained4 ,if pure1 the crystals would be colorless1 but impurities of iron and titanium give it the dark-brown to black color4 ,cassiterite may appear very like rutile1 the crystalline forms being identical1 but the reddish tinge of color in the rutile will separate the two4 ,cassiterite is one of those minerals which result from deposition at very high temperatures1 probably from vapors1 and is found in the veins in igneous rocks1 such as light-colored granites1 gneisses1 syenites1 etc4 ,while not mined in this country it is found in small quantities in ,maine1 ,massachusetts1 ,new ,hampshire1 ,virginia1 ,alabama1 ,wyoming1 ,montana1 and ,california4 ,titanium ,titanium1 as a metal1 is a heavy1 gray1 iron-like powder1 which is chiefly useful as an alloy with iron1 giving it toughness1 and preventing bubbles and cracks in casting4 ,it is not as rare as some other metals which have found a wider use4 ,rutile ,ti,o ,pl4 #bh ,occurs in tetragonal crystals1 and in grains2 hardness #f4e2 specific gravity #d4b2 color red to reddish-brown2 streak yellowish-brown2 luster metallic to adamantine2 translucent on thin edges4 ,rutile usually occurs in crystals1 which are either short and stout1 or in needle-like crystals4 ,twinning is common4 ,in form and general appearance it resembles cassiterite1 but the reddish color1 and the yellowish-brown streak will distinguish the rutile4 ,it is found in similar rocks1 granites1 gneisses1 syenites1 and mica-schists1 the two minerals cassiterite and rutile often occurring together4 ,this is also true of the grains1 which have been weathered out and are found in sands and gravels of placer deposits4 ,it is found in small quantities in all the ,new ,england ,states1 ,new ,york1 and all down the ,appalachian ,mountains1 especially at ,graves ,mountain1 ,ga41 and in ,arkansas and ,alaska4 ,ilmenite ,fe,ti,o ,occurs in granular masses1 as black sand1 or as tabular hexagonal crystals2 hardness #e-f2 specific gravity #d4g2 color black2 streak brownish-red to black2 luster metallic2 opaque on thin edges4 ,when ilmenite occurs in crystals they are tabular and resemble hematite in its darker varieties1 but the streak readily distinguishes the two4 ,in masses it looks like magnetite1 but the lack of magnetism serves to distinguish these two minerals4 ,it is very likely to be associated with cassiterite1 rutile1 or magnetite in grains which have weathered out of the original rock1 and have resisted solution and wear4 ,sands with a large amount of the above mentioned minerals are termed 8black sands10 some of which are important for one or another of these minerals4 ,ilmenite is a mineral formed at high temperatures1 and probably often deposited from hot vapors4 ,it is found in granites1 syenites1 and gneisses4 ,among the better known localities are ,orange1 ,n4 ,y41 ,litchfield1 ,conn41 ,florida1 ,california1 etc4 ,platinum ,this metal is steel-gray in color1 very malleable and ductile1 almost infusible and resists the action of acids4 ,it is one of the 8noble0 metals1 much rarer than gold1 and so has become popular for jewelry4 ,it is also used in the manufacture of sulphuric-acid1 in nitrogen-fixation plants1 for chemical utensils1 in the electrical industries1 and in dentistry4 ,platinum in its occurrence is associated with the certain other equally rare elements1 like iridium1 palladium and osmium4 ,its use has increased rapidly of late1 but the supply has not kept up with the demand1 so that1 whereas in #aijf platinum and gold were about equally valuable1 now the platinum brings about five times as much as the gold4 ,platinum ,pt ,occurs in grains or nuggets2 hardness #d4e2 specific gravity #ai 7#ba if pure72 color steel-gray2 luster metallic2 opaque4 ,this rare metal is mostly found in placer-deposits1 often with gold4 ,it comes originally from dark igneous rocks1 like peridotite1 pyroxenite1 etc41 and platinum is found to be associated with the nickel ores of ,sudbury1 ,canada4 ,while formerly #ij of the world's supply of platinum came from placer mines in the ,ural ,mountains1 today more than half is produced in ,canada and about a fifth in ,russia4 ,in the ,united ,states it is found in ,california1 ,oregon1 ,nevada1 and ,alaska4 ,the ,magnesium ,group ,magnesium is a silvery-white metal1 easily tarnished by exposure to moist air4 ,because of its light weight1 less than twice the weight of water1 and strength1 it is being substituted for aluminum1 especially in airplanes1 where the question of weight is crucial4 ,it is also used in automobile and ship production and other machine industries1 and in the manufacture of flares and incendiary bombs4 ,magnesium is obtained chiefly from magnesite1 dolomite1 and in the ,united ,states as a result of a recently developed process1 from sea water4 ,magnesium has a considerable number of minerals1 of which three are taken up here and several more under the head of silicates1 where both magnesium and silicon are combined in a mineral4 ,spinel ,mg,al,o ,pl4 #bi ,occurs mostly as isometric octahedrons2 hardness #h2 specific gravity #c4e2 color1 red1 yellow1 green1 or black2 streak white2 luster vitreous2 transparent on thin edges4 ,this is a rather rare mineral1 but1 when in clear crystals is considered one of the gems4 ,it was early confused with corundum1 and the red variety called ruby1 as it was found in the same gem-bearing sands in ,ceylon1 ,burma1 and ,siam4 ,however the form of the isometric octahedron as compared with the hexagonal prism of the corundum1 together with the lesser hardness are sufficient to distinguish the two easily4 ,the crystals are usually octahedrons1 but may have the corners cut or the edges beveled4 ,twins are not uncommon4 ,the standard color is a clear deep-red1 and such a spinel is known in the gem trade as a spinel-ruby4 ,if the color is rose-red1 it is a ,balas ruby2 if orange1 it is rubicelle1 if of a violet tinge1 almandine4 ,when small quantities of other elements replace the magnesium1 the color is greatly changed4 ,for example a little iron present gives the crystals a dark-green to black color1 and the spinel is known as ceylonite4 ,if there is both iron and chromium present1 the color becomes yellowish or greenish-brown1 and this variety is picotite4 ,when the impurities are iron and copper1 the color becomes grass-green1 and it is called chlorospinel4 ,a form1 in which the magnesium is completely replaced by iron1 is black in color and termed hercynite1 and occurs fairly abundantly in ,westchester ,co41 ,n4 ,y4 ,from ,amity1 ,n4 ,y41 to ,andover1 ,n4 ,j41 there is a belt of granular limestone in which spinel of all colors is found4 ,st4 ,lawrence ,co41 ,n4 ,y41 is also a rich locality4 ,bolton1 ,mass41 ,newton1 ,sterling1 and ,sparta1 ,n4 ,j41 ,north ,carolina1 ,alabama1 and ,california all yield spinel4 ,magnesite ,mg,c,o ,occurs in cleavable or compact porcelain-like masses2 hardness #d2 specific gravity #c4a2 color white to gray2 luster vitreous2 translucent on thin edges4 ,magnesite is white and brittle1 and cleaves perfectly parallel to the faces of the rhombohedron1 but it seldom occurs in crystals4 ,it will effervesce in warm hydrochloric acid and has some resemblance to calcite1 but can be distinguished by the greater hardness4 ,it is still more like dolomite1 both having the same color and cleavage1 both effervescing in warm hydrochloric acid2 but the magnesite has half a point greater hardness and the porcelainous appearance4 ,magnesite is used in toilet preparations1 paper making1 and mixed with asbestos1 as a covering for heating pipes4 ,magnesite is found in ,massachusetts1 ,pennsylvania1 ,texas1 and in large deposits in ,california and ,washington4 ,dolomite 7,mg,ca7,,co ,pl4 #ai #bi ,occurs in crystals1 or in cleavable or granular masses2 hardness #c4e2 specific gravity #b4h2 color white to pink or gray2 streak white2 luster vitreous2 transparent on thin edges4 ,dolomite crystallizes in the hexagonal system1 in rhombohedrons 7hemihedral form71 which are more or less modified by faces on the corners or edges4 ,the cleavage is parallel to the rhombohedron1 and it will effervesce in warm hydrochloric acid4 ,sometimes the crystal faces are curved1 and when this is the case1 dolomite is easily determined4 ,usually however dolomite resembles both calcite and magnesite4 ,from the calcite it is distinguished by the greater hardness1 and from magnesite by lesser hardness and not being porcelainous in appearance4 ,some of the commoner forms are shown on ,plate #bi1 crystals like ,c being found embedded in anhydrite and gypsum4 ,magnesium is a common element and is likely to be present wherever lime is being deposited1 so dolomite crystals are common1 and much of the limestone is dolomitic4 ,it may be found in almost any limestone section of the country4 ,some of the finest crystals of dolomite however come from ,roxbury1 ,vt41 ,smithfield1 ,r4 ,i41 ,hoboken1 ,n4 ,j41 ,lockport1 ,rochester1 and ,niagara ,falls1 ,n4 ,y41 etc4 ,silicon1 ,silica and the ,silicates ,silicon is one of the non-metallic elements1 and does not occur as such in ,nature4 ,when isolated it is either a dark-brown powder1 or steel-gray crystals4 ,however silicon is next to oxygen in its importance in making the crust of the earth4 ,forty-seven per cent of the surface rocks are composed of oxygen1 and #bh of silicon1 the latter appearing in a host of minerals4 ,the oxide of silicon is termed silica 7,si,o71 its crystal form being quartz1 the commonest of all minerals4 ,in non-crystalline form silica is also widely distributed1 as chalcedony and opal1 even appearing in the tissues of animals and plants1 as in the feathers of birds1 the shells of certain ,protozoa 7,radiolaria71 the spicules of sponges2 and in plants1 as the shells of diatoms1 and in the stalks of grasses1 especially cereals and bamboo4 ,silica in the form of sand is widely used in making glass1 porcelain1 china1 etc41 and in the various cements4 ,then there are a considerable number of acids of silicon1 which do not occur in ,nature1 but their salts do1 and make a host of minerals1 which are known as the silicates1 such as mica1 feldspar1 hornblende1 etc4 ,either as quartz1 or as silicates1 silicon is represented in most all the igneous and metamorphic rocks and in many of the sedimentary rocks4 ,quartz ,si,o ,pl4 #cj ,occurs as hexagonal crystals1 or in grains or masses2 hardness #g2 specific gravity #b4fe2 colorless when pure2 luster vitreous2 transparent on thin edges4 ,quartz is not hard to identify4 ,its hardness and the crystal-form separate it from most all other minerals4 ,it is the most common mineral1 making #ab of the earth's crust4 ,the usual crystal form is a hexagonal prism with the sides horizontally striated1 and a six-sided pyramid on one or both ends4 ,this six-sided pyramid is really two rhombohedrons1 a right-handed one and a left-handed one1 so that the alternate faces of the pyramid may show peculiarities1 for instance three may be large and three small1 as in ,fig4 ,b1 ,plate #cj1 or the alternate ones may be duller or etched in some manner4 ,the crystals are clear and when pure colorless1 but there is a tendency for some slight impurity to color them almost any hue4 ,the most perfect double-ended crystals form only where growth is possible in all directions1 as in clay4 ,in cavities and caves there is an opportunity for the crystals to grow in toward the open spaces1 and in such places1 one finds fine large crystals2 the ,alps1 ,brazil1 ,japan1 and ,madagascar being especially famous localities4 ,the largest quartz crystal on record is one #be feet in circumference which came from ,madagascar4 ,in this country the caves at ,little ,rock1 ,ark41 have furnished some very fine large crystals4 ,smaller1 but very clear crystals1 come from about ,herkimer1 ,n4 ,y4 ,some of these have been used as 8,rhine-stones0 and as cheap imitations of diamonds4 ,clear quartz is beautiful enough to be a gem1 but it is too common to interest people as jewelry1 however many objects of art have been carved from it4 ,one of these took the form of crystal balls1 which1 through the ,middle ,ages particularly1 developed into a form of mysticism4 ,the gazing into the crystal ball was supposed to give some people supernatural vision4 ,it seems to be a form of hypnotism1 gazing at the bright reflecting surface tiring the eye1 and making possible visions1 which are subjective rather than anything external4 ,silica is slightly soluble in water1 especially when it is alkaline2 so that most river-1 lake-1 and sea-waters have some silica in solution1 and are carrying it from one place to another4 ,the waters1 which percolate through the rocks1 carry even more1 and when they come out into open spaces1 they give up some of the silica1 making crystals lining these openings1 whether fissures or cavities4 ,not infrequently these silica-bearing waters dissolve out some other crystal1 and then deposit in its place silica1 thus making a crystal which has the form of what was dissolved1 rather than that of quartz4 ,such a form is known as a pseudomorph4 ,when molten masses of igneous rock were cooling the quartz crystals had their faces interfered with as they grew1 and we have resulting crystalline quartz1 simply filling in the spaces between the other crystals1 such as feldspar and mica1 in the granite4 ,quartz is a large component in many igneous rocks1 also in metamorphic rocks1 and certain sedimentary rocks like sandstone are almost wholly made up of quartz grains4 ,quartz is also the gangue mineral in many veins4 ,in this case it seems to have been deposited from hot water or vapors1 as they rose from cooling magmas4 ,with it are associated all sorts of metallic ores as has been suggested4 ,quartz has been largely used to make imitations of other much rarer minerals1 sometimes in its crystalline form to imitate the diamond1 at other times ground and made into a 8paste10 which is colored to imitate other gems4 ,this paste is a mixture of about #d parts of quartz1 #e parts of red lead and #a part of potassium carbonate1 melted and cooled slowly4 ,it is clear and has a brilliant luster like the diamond4 ,if some coloring matter is put into it it can be used for rubies1 sapphires1 etc4 ,when there is any reason to think that this is being used1 it is easily detected by being so much softer than any of the true gems1 and even than true quartz4 ,quartz will scratch glass readily1 but this imitation has only the hardness of very soft glass1 or about #e4 ,varieties of ,quartz ,rock crystal is the term applied to quartz when it is clear and colorless4 ,milky quartz is the milky variety1 the whiteness being due to imperfections in the crystallization1 such as cracks1 bubbles1 etc4 ,smoky quartz is the cloudy brown-colored variety1 which results from the presence of small quantities of organic matter 7hydrocarbons7 in the quartz4 ,if the color is so dark as to be almost black it is termed morion4 ,in the above cases the color will disappear if the stone is heated4 ,pebbles of smoky quartz from ,cairngorm1 ,scotland1 have been so widely used as semiprecious stones that they have come to be known as cairngorms4 ,citrine1 or false topaz1 is a clear yellow variety1 the color again due to the presence of organic matter4 ,it is distinguished from true topaz by the lesser hardness1 this having the hardness of #g1 while true topaz has a hardness of #h4 ,amethyst is quartz with a violet color1 due to the presence of small quantities of manganese4 ,to be suitable for cutting into gems1 the color must be deep or the small pieces will appear almost colorless4 ,it is widely used today as a semiprecious stone in jewelry2 and in the fifteenth century it had the traditional virtue of making the wearer sober-minded1 whether he had taken too freely of wine1 or was over excited by love-passion4 ,rose quartz gets its pale-red color from the presence of a small amount of titanium4 ,it is widely distributed1 but is more abundant in the ,black ,hills of ,south ,dakota4 ,aventurine is quartz which has inclosed tiny scales of mica or hematite giving it a spangled appearance4 ,prase is a green quartz1 the color being due to the inclusion of fibrous crystals of green actinolite4 ,cat's ,eye is a quartz which has inclosed silky fibers of asbestos4 ,when this is cut parallel to the fibers1 the effect is opalescent4 ,the colors are greenish1 yellowish-gray1 and brown4 ,this form1 however1 is not to be confused with the true or ,oriental ,cat's ,eye1 which is chrysoberyl and has the hardness of #h4 ,chalcedony ,si,o ,non-crystalline1 occurring in botryoidal1 stalactitic or concretionary masses2 hardness1 #g2 specific gravity1 #b4fe2 color white when pure2 luster waxy2 translucent to transparent on thin edges4 ,in addition to the crystalline form1 silica is freely deposited in an amorphous or cryptocrystalline form which has the same properties as quartz1 except the crystal faces4 ,this is called chalcedony1 and it occurs in seams1 cavities and free surfaces4 ,when the surface of a chalcedony deposit is free it has a waxy luster4 ,it is generally very brittle and breaks in a peculiar splintery manner4 ,like quartz it also has a great many varieties1 according to the impurities present4 ,its wide distribution1 hardness1 and the manner in which it can be chipped have made this a most important stone in the history of the development of civilization4 ,the early men first broke it into rough tools1 such as knives1 axes1 spear points1 etc41 and used these as cutting tools1 of one sort or another1 because they held their edge better than most stones4 ,we apply1 to the people who used only these chipped stones as tools1 the term 8,men of the ,old ,stone ,age10 or the period is termed the ,palolithic ,age4 ,later men learned how to grind the edge to a smoother outline1 and this much shorter period is termed the ,neolithic ,age4 ,the use of flints for the first tools is world-wide1 and the ,american ,indian when discovered was still using chalcedony in its rough-hewn state4 8,there the ancient ,arrow-maker ,made his arrow heads of sandstone1 ,arrow heads of chalcedony1 ,arrow heads of flint and jasper1 ,smoothed and sharpened at the edges1 ,hard and polished1 keen and costly40 ,chalcedony is the proper term to use when the color is white to translucent1 in which case the surfaces are usually botryoidal and waxy4 ,carnelian is chalcedony which is clear red in color and translucent4 ,this is one of the first stones used for ornamental purposes and for engraving4 ,carnelians with figures engraved on them were used by the ,egyptians1 ,assyrians and ,the ,children of ,israel1 at least #bjjj ,b4,c42 and the ,egyptian scarabs of the fifth or sixth century ,b4,c41 were often carved from this variety of chalcedony1 as well as from jasper and agates4 ,the brownish varieties are termed sard4 ,chrysoprase is an apple-green variety of chalcedony the color being due to the presence of nickel oxide4 ,this is by no means as common as most of the varieties of chalcedony1 and was long prized as a gem4 ,plasma is chalcedony with a leek- to emerald-green color1 and the same stone when it has small red spots of jasper in it is termed blood-stone1 or heliotrope4 ,these red spots are said by tradition to be drops of the blood of ,christ4 ,jasper is a deep red chalcedony1 the color being due to hematite1 which is so abundant as to make it opaque4 ,a brown variety colored by limonite is also called jasper1 and even green jaspers are found4 ,in all cases the opaque character is common4 ,flint is an impure brown chalcedony1 usually forming concretions4 ,the color is due to organic matter4 ,flint is mostly found in limestone or chalk1 and the concretions are the result of the small particles of silica scattered through the rock being dissolved1 and then reprecipitated about some organic center4 ,generally the silica was obtained by the dissolution of small fossils1 like the shells of diatoms or sponge spicules4 ,hornstone and ,chert are simply impure varieties of flint1 brown in color1 and with a splintery fracture4 ,agate1 ,plate #cb1 is a banded or cloudy chalcedony which has formed in a cavity1 the layers of different color representing deposition from water1 carrying first silica with one impurity1 then later1 silica with another impurity4 ,gradually the cavity has been thus filled with silica2 and when the mass is freed by the weathering away of the surrounding rock1 these banded masses are found4 ,sometimes the manner of deposition has changed1 and while the outer part of the cavity was filled with chalcedony1 the central part will contain quartz crystals4 ,on account of the beauty of the colors1 and the unusual way in which they may be developed1 agates are widely used for semiprecious jewelry and objects of art1 and this has been true since ancient times1 the name itself coming from the ,river ,achates in ,sicily4 ,the center for cutting and polishing agates is at ,oberstein1 ,germany1 where this work has been carried on since the middle of the fifteenth century4 ,in spite of the many fine natural colors in agates1 they are sometimes artificially colored1 in many cases by methods which are kept as 8trade secrets40 ,the color seldom penetrates far2 so that even slight chipping reveals whether an inferior agate has been taken and colored up1 or whether the stone is natural4 ,moss agates are chalcedony which has inclosed dendritic masses of some one of the manganese compounds as shown under manganite1 p4 #gc4 ,onyx is a variety of agate where the bands are alternately black and white2 while sardonyx is agate with red or brown bands alternating with the white4 ,such agates as these are especially desirable for cameo work1 where the figure is carved in the chalcedony of one color1 and the other color makes the background4 ,silicified or agatized wood is a form of chalcedony1 where silica has replaced wood1 molecule by molecule2 so that in good specimens1 all the structure of the wood is still retained1 and when thin sections are made it can be studied under the microscope almost as well as modern wood4 ,this takes place under water1 usually1 if not always1 in fresh water4 ,such fossilized wood is widely distributed in the western ,united ,states1 the most famous cases being the ,fossil ,forest of ,arizona1 now a ,national ,reservation1 and the fossil trees in the ,yellowstone ,national ,park4 ,opal ,si,o,h,o ,pl4 #cc ,non-crystalline1 massive1 stalactitic or nodular2 hardness1 #f2 specific gravity #b2 all colors2 luster vitreous1 resinous1 or pearly2 transparent on thin edges4 ,opal differs from chalcedony in having water1 usually about #aj1 incorporated in its structure4 ,this is water of crystallization1 and not firmly held2 so that1 if opal is heated in a closed tube to above #ajj ,c41 it is given off as a vapor4 ,opal is distinguished from chalcedony by its lesser hardness1 and the resinous to pearly luster4 ,it forms in cavities1 in layers often of extreme thinness4 ,opal is originally the product of the dissolution of silicate minerals in hot acid waters1 the resulting gelatinous silica1 when it is deposited and hardened1 becoming the opal4 ,there are many varieties1 some of them highly prized as gems in spite of the moderate hardness and opacity of the mineral4 ,gem-quality opal gets its opalescent character from the successive deposition of thin films of opal1 the light penetrating and being reflected from different films4 ,this breaks up the white light and causes the play of colors which is the charm of this gem4 ,precious opal1 in which the play of colors is finest1 comes mostly from ,hungary1 ,mexico1 and ,queensland4 ,the opal was a favorite stone from before ,roman times1 and in its early history was a charm against the 8evil eye40 ,during the nineteenth century for some reason it came to be considered an unlucky stone4 ,fire opal is a hyacinth-red to honey-yellow variety1 which has a fire-like play of color1 and is found in ,mexico and ,honduras4 ,common opal does not have the play of color1 but comes in a variety of colors2 is waxy or greasy in luster2 and occurs mostly as fillings of seams or cavities1 especially those in igneous rocks1 like the steam holes in lavas1 etc4 ,it is found in ,cornwall1 ,penn41 in ,colorado1 ,california1 etc4 ,opal-agate is a variety in which there are color bands1 and it is widely distributed4 ,opalized wood is formed in exactly the same manner as agatized wood1 much of the fossil wood called silicified being really opalized4 ,siliceous sinter is the porous mass of opal which is so frequently deposited about hot springs and geysers4 ,it is readily recognized by its porous character4 ,the shells of the diatoms1 which are microscopic plants1 are made of opal2 and while they are so small1 there is certainly no other plant so abundant or omnipresent1 living as it does in every pool1 lake1 or sea by the millions4 ,these shells are very indestructible so that they accumulate at the bottom of ponds1 bogs1 and sea-bottoms1 making at times extensive deposits4 ,this material in quantities is termed diatomaceous earth1 or tripolite 7from ,tripoli where it was first used commercially74 ,it is used as a polishing powder for metals1 marble1 glasses1 etc4 ,the ,feldspars ,the term feldspar is a family name for a large variety of very common minerals1 which altogether make up nearly #fj of the crust of the earth1 being the predominant part of granites1 gneisses1 and lavas4 ,in composition they are silicates of aluminum1 together with potassium1 sodium and calcium1 and their mixtures4 ,they may be tabulated as follows3 #a4 ,k,al,si,o1 orthoclase1 the silicate of aluminum and potassium4 #b4 ,na,al,si,o1 albite1 the silicate of aluminum and sodium4 #c4 ,ca,al,si,o1 anorthite1 the silicate of aluminum and calcium4 #d4 ,mixtures of #a and #b are alkalic feldspar4 #e4 ,mixtures of #b and #c are plagioclase feldspar4 ,orthoclase is monoclinic1 but the rest of the feldspars are triclinic4 ,if crystals are available they may be short and stout1 or tabular and thin1 but as the feldspars are mostly components of the igneous rocks1 where perfect crystals have not had a chance to grow1 they are mostly determined by their hardness and cleavage4 ,the hardness of all the feldspars is #f or very close to it4 ,they all have three planes of cleavage1 two of which are good and intersect either at #ij as in orthoclase1 or at about #hf as in the plagioclase series2 while the third cleavage plane is imperfect4 ,in figure #a1 ,plate #cd1 a and b are the two perfect cleavages1 while c is the imperfect one4 ,breaking into such cleavage masses as the one illustrated is characteristic of feldspar4 ,the specific gravity ranges from #b4ee to #b4ge4 ,the luster is vitreous1 and the color white1 ranging to various shades of gray and pink1 and1 sometimes in recent lavas1 colorless4 ,twinning is very common and helps to distinguish orthoclase from the plagioclase feldspars4 ,in orthoclase the twins are simple1 that is1 only two crystals growing together1 and are united on one of the faces1 as if one of them had been revolved #ahj with the other2 or1 while related to each other as in the preceding case1 they may seem to grow through each other4 ,on plate #cd are three orthoclase crystals showing this simple type of twinning4 ,the first 7,a7 is a simple crystal2 the second 7,b7 shows the simplest type of twinning where the left-hand crystal has revolved #ahj on the p face1 and the end is composed1 half of the upper end of one crystal1 and half of the lower end of the adjacent crystal4 ,the presence of rentrant angles calls attention to the twinning4 ,the third figure 7,c7 is a case of intergrowing crystals4 ,in the plagioclase feldspars twinning is multiple1 a large number of crystals1 each thin1 sometimes as thin as paper1 growing side by side1 the first one in normal position1 the next at #ahj with it1 the third revolved #ahj to the second and thus parallel to the first1 and so on4 ,the result is first of all a striated appearance1 and second that1 as plagioclase crystals have their prism faces intersecting at #hf1 there is a series of low roofs and valleys1 which are best seen by holding the piece of feldspar so the light reflects from a cleavage face1 when it will appear striated2 then by tilting it about #h degrees a second set of reflections1 also appearing striated1 will appear4 ,the light was first reflected from one side of the roofs1 and in the second case from the other side4 ,figure ,d1 ,pl4 #cd1 is a diagram showing the relation of the individual crystals in a multiple twinned piece of plagioclase1 in which the crystals are represented as rather large4 ,plate #ce1 under labradorite1 shows a photograph of a cleavage piece1 on which is readily seen the striation which is characteristic of the plagioclase feldspars4 ,mixtures of albite and anorthite occur in bewildering numbers1 one or the other predominating1 and each mixture being uniform throughout the crystal and in the whole mass2 so each combination is a mineral1 each with its special properties2 but the different plagioclase feldspars are so similar in appearance1 that by the naked eye it is impossible to separate the closely related ones4 ,this can be done under the microscope by studying the angles at which light is cut off1 and also by chemical analyses4 ,for our purposes six types will suffice to illustrate the group1 and their composition may be indicated as follows4 ,albite is albite with up to #ae of anorthite mixed with it4 ,oligoclase is albite with from #ae-be of anorthite mixed with it4 ,andesite is albite with from #be-ej of anorthite mixed with it4 ,labradorite is anorthite with from #be-ej of albite mixed with it4 ,bytownite is anorthite with from #ae-be of albite mixed with it4 ,anorthite is anorthite with up to #ae of albite mixed with it4 ,the best method for distinguishing these feldspars of the plagioclase group is to measure the angle between the two perfect cleavage faces1 and even this requires careful measurement4 ,the angles between these faces are as follows3 ,orthoclase #ij ,microcline #hi #cj ,oligoclase #hf #cb ,andesite #hf #ad ,labradorite #hf #ad ,bytownite #hf #ad ,anorthite #hf #ej ,orthoclase ,k,al,si,o ,occurs in granites1 syenites1 gneisses and light-colored lavas2 hardness1 #f2 specific gravity1 #b4eg2 color white to gray or pink2 cleavage in two directions perfect and at #ij1 in the third direction imperfect2 luster vitreous2 translucent on thin edges4 ,orthoclase is monoclinic1 and when formed in cavities develops as crystals1 but it is usually a constituent of igneous rocks1 in which case the crystals have not had the opportunity to develop the crystal faces1 and the orthoclase is in grains or irregular masses2 and the best way of determining the mineral is the cleavage1 the two perfect cleavage planes intersecting at right angles4 ,twinning is frequent but of the simple type1 only two crystals being united1 similar to either ,b or ,c on plate #cd4 ,it is found in granites1 gneisses or lavas1 wherever they occur1 being especially characteristic of the granites of the ,rocky ,mountains4 ,microcline ,k,al,si,o ,pl4 #ce ,occurs in granites and gneisses as crystals or irregular masses2 hardness1 #f2 specific gravity1 #b4ef2 color white to gray1 pink1 or greenish2 luster vitreous2 translucent on thin edges4 ,microcline has the same composition as orthoclase1 but is in the triclinic system1 the c axis being inclined a half degree away from a right angle with the b axis4 ,this is best seen in the cleavage pieces1 the two perfect cleavage planes meeting at #hi #cj1 and this is the only test for determining this mineral by the unaided eye4 ,pike's ,peak is the best known locality for microcline1 and there it occurs in fine large crystals of greenish color1 which are known as ,amazon stone4 ,albite ,na,al,si,o ,occurs in small crystals1 or more often in lamellar masses in granites or in seams in metamorphic rocks2 hardness1 #f2 specific gravity1 #b4fb2 color white to gray2 luster vitreous4 ,albite may occur in simple crystals1 in which case the two perfect cleavage planes meet at an angle of #hf #bd4 ,however1 it is much more frequently found twinned in the multiple manner1 the individual crystals often being as thin as paper4 ,this gives rise to a fine striation on the end of a crystal1 or on the surface made by the imperfect cleavage plane4 ,where the crystals are extremely thin1 the surface may have a pearly luster4 ,albite types of granite often inclose secondary minerals1 that are prized as gems1 such as topaz1 tourmaline1 and beryl4 ,it is found at ,paris1 ,me41 ,chesterfield1 ,mass41 ,acworth1 ,n4 ,h41 ,essex ,co41 ,n4 ,y41 ,unionville1 ,penn41 and in ,virginia1 and throughout the ,rocky ,mountains4 ,oligoclase 7,na,ca7,al,si,o ,generally found in cleavable masses in granites and lavas1 rarely in crystals2 hardness1 #f2 specific gravity1 #b4fe2 color white1 greenish or pink2 luster vitreous2 translucent on thin edges4 ,oligoclase is a plagioclase feldspar and is distinguished by its two perfect cleavage planes meeting at an angle of #hf #cb1 but otherwise it is very like albite4 ,crystals are not common1 and it occurs mostly in masses1 making one of the components of granite or lava4 ,it is found in ,st4 ,lawrence ,co41 ,n4 ,y41 ,danbury and ,haddam1 ,conn41 ,chester1 ,mass41 ,unionville1 ,penn41 ,bakersville1 ,n4 ,c41 etc4 ,labradorite 7,na,ca7,al,si,o ,pl4 #ce ,usually found in cleavable masses in granites and lavas2 hardness1 #f2 specific gravity1 #b4ga2 color gray or white1 often with a play of colors2 luster vitreous2 translucent on thin edges4 ,labradorite is distinguished by having the two perfect cleavage planes meet at #hf #ad4 ,the iridescent play of color is also very characteristic and is generally present4 ,it is due to the inclusion of minute impurities4 ,this feldspar is usually associated with granites or lavas in which the dark minerals predominate4 ,it gets its name from being the feldspar of the granites of ,labrador1 and is also found in the granites of the central part of the ,adirondack ,mountains and the ,wichita ,mountains of ,arkansas4 ,the ,pyroxene ,group ,the minerals of this group are generally associated with feldspars1 and make the dark-colored component of granites1 gneisses and lavas4 ,this is especially true of those which have some iron in the crystal4 ,pyroxenes are salts of metasilicic acid 7,h,si,o71 in which the hydrogen 7,h7 has been replaced by calcium1 magnesium1 iron1 etc4 ,the commoner minerals are orthorhombic or monoclinic1 and all agree in their crystal habit1 being short stout prisms1 with the vertical edges so beveled that a cross section is eight-sided4 ,the cleavage is good in two directions1 parallel to the beveling faces 7m in figure b1 ,plate #cf71 and they intersect at an angle of #hg4 ,this is very characteristic1 and if one has a crystal broken across1 it is easy to see and measure this angle of intersection4 ,these pyroxenes have the same chemical composition as the corresponding series of amphiboles1 but the two are distinguished by several features4 ,pyroxenes are short and stout crystals1 while amphiboles are long and either blade- or needle-like2 pyroxenes are eight-sided in cross section1 while amphiboles are six-sided2 in pyroxenes the cleavage planes intersect at #hg1 while in amphiboles they intersect at #ee4 ,the minerals of this group are most frequently one of the components of a lava or granite1 and are less frequently associated with metamorphic rocks4 ,three are common2 enstatite1 hypersthene1 and augite4 ,enstatite ,mg,si,o ,usually occurs in lamellar or fibrous-lamellar masses in dark lavas2 hardness1 #e4e2 specific gravity1 #c4c2 color gray1 bronze or brown2 luster vitreous1 translucent on thin edges4 ,enstatite rarely occurs in crystals1 but when it does they are orthorhombic4 ,usually it is in irregular masses with the cleavage angles1 typical of pyroxene4 ,the color is light1 that is gray or brownish1 and the streak white or nearly so4 ,in most respects it is similar to hypersthene1 which has the same composition1 except that a large part of the magnesium is replaced by iron1 and there are all sorts of gradations between the two minerals4 ,when some iron takes the place of magnesium1 the color darkens to1 or towards bronze1 until when about a third of the magnesium is so replaced1 and the color is fully bronze1 this variety is called bronzite4 ,bronzite is present in some of the dark lavas like gabbro and peridotite4 ,enstatite is found in the ,adirondack ,mountains1 at ,brewster and ,edwards1 ,n4 ,y41 etc4 ,hypersthene 7,mg,fe7,si,o ,occurs in cleavable masses in dark lavas2 hardness1 #e4e2 specific gravity1 #c4d2 color dark-brown or greenish-brown2 luster vitreous2 translucent on thin edges4 ,hypersthene is a pyroxene in which magnesium and iron are present in about equal quantities4 ,it is similar to enstatite1 except that the color is darker1 and the streak gray or brownish-gray in color4 ,these two minerals grade into each other1 so that there are cases where it is simply a matter of preference as to which name should be given to the mineral4 ,this form is associated with dark lavas1 of the gabbro or peridotite type1 in such places as the ,adirondack ,mountains1 ,mount ,shasta in ,california1 ,buffalo ,peaks1 ,colo41 etc4 ,augite ,ca,mg7,si,o71 ,mg,al,si,o ,fe,o ,pl4 #cf ,usually occurs in short stout monoclinic crystals2 hardness1 #e4e2 specific gravity1 #c4c2 color dark-green to black2 luster vitreous2 translucent on thin edges4 ,augite is a complex pyroxene having some iron and aluminum always present in it1 but the amount not a fixed quantity4 ,it is by far the commonest of the pyroxenes and has a wide distribution1 both in the sorts of lavas in which it appears1 and in the world4 ,it is commonly the dark component of such lavas1 as gabbros and peridotites1 and also is common in metamorphic rocks1 especially impure crystalline limestones4 ,it is found at ,raymond and ,mumford1 ,me41 ,thetford1 ,vt41 ,canaan1 ,conn41 in ,westchester1 ,orange1 ,lewis and ,st4 ,lawrence ,counties of ,n4 ,y41 in ,chester ,co41 ,penn41 at ,ducktown1 ,tenn41 ,templeton1 ,canada1 etc4 ,the ,amphibole ,group ,the amphiboles are a group of minerals made up of the same chemical elements as the pyroxenes1 but with the molecular arrangement different1 which appears in the forms of the crystals4 ,the commoner ones are all monoclinic but contrast with the pyroxenes as follows4 ,amphiboles are long and slender crystals1 while pyroxenes are short and stout2 amphiboles are six-sided1 while pyroxenes are eight-sided2 amphiboles have the two perfect cleavages intersecting at #ee and #abe1 while those of pyroxene intersect at #hg and #ic4 ,with the above in mind it is easy to place the minerals in their proper group1 but inside the group it is not always so easy to distinguish one from another4 ,this group is associated rather with metamorphic rocks than with igneous rocks1 with which the pyroxenes are mostly associated4 ,the three commoner minerals of the group are tremolite1 actinolite1 and hornblende4 ,tremolite 7,ca,mg77,si,o7 ,pl4 #cg ,occurs in long prismatic crystals or in columnar or fibrous masses2 hardness #e4e2 specific gravity1 #c2 color white to gray2 luster vitreous2 transparent on thin edges4 ,the long prismatic crystals of tremolite occur especially where dolomitic limestones have been altered by metamorphism4 ,sometimes these crystals grow side by side1 making fibrous masses1 where the long slender crystals can be picked apart with the fingers1 and yet are flexible1 and tough enough so that they can be felted together4 ,this is termed asbestos1 which1 because it is infusible and a poor conductor of heat1 is much used to make insulators1 fire-proof shingles1 and all sorts of fireproof materials4 ,the varieties in which the crystals are finer and silky in appearance1 like the one illustrated on ,plate #ch are termed amianthus4 ,there are other minerals1 such as actinolite and serpentine1 which occur in the same manner1 and are also called asbestos1 the serpentine variety being just now the most important commercially4 ,tremolite is found at ,lee1 ,mass41 ,canaan1 ,conn41 ,byram1 ,n4 ,j41 in ,georgia1 etc4 ,actinolite 7,ca,mg,fe77,si,o7 ,occurs in radiating crystals1 or in fibrous masses2 hardness1 #e4e2 specific gravity #c2 color pale- to dark-green2 luster vitreous2 translucent on thin edges4 ,except for its green color1 this mineral is very like tremolite4 ,the difference between the two is due to the small amount of iron in the actinolite4 ,it is usually found in schists1 and the radiating character of the crystal groups is enough to determine the mineral1 if it is already clear that it is one of the amphiboles4 ,occasionally it occurs with the crystals parallel to each other1 making one of the forms of asbestos4 ,actinolite is found at ,warwick1 ,edenville1 and ,amity in ,orange ,co41 ,n4 ,y41 at ,franklin and ,newton1 ,n4 ,j41 ,mineral ,hill and ,unionville1 ,penn41 ,bare ,hills1 ,md41 ,willis ,mt41 ,va41 etc4 ,hornblende 7,ca,mg,fe77,si,o7,ca,mg,al7,si,o7 ,pl4 #cg ,occurs in well-defined crystals1 in grains and in masses2 hardness1 #e4e2 specific gravity #c4b2 color black1 dark-green1 or dark-brown2 luster vitreous2 translucent on thin edges4 ,in composition hornblende corresponds to augite1 but occurs in long slender1 six-sided crystals with cleavage planes intersecting at #ee1 so that it is a typical amphibole4 ,it occurs in a very wide range of rocks1 such as granite1 syenite1 diabase1 and gabbro2 and in such metamorphic rocks as schists and gneisses2 and sometimes igneous rocks are made up almost entirely of hornblende1 when they are known as amphibolites or hornblendite4 ,it is found all through the ,new ,england ,states1 down along the ,piedmont ,plateau1 through the ,blue ,ridge ,mountains1 and in many of the western mountainous areas4 ,the ,garnet ,group ,the garnets are a series of double silicates1 which occur with surprisingly uniform characters4 ,they are all isometric1 and occur either as dodecahedrons1 or as the #bd-sided figure 7the trapezohedron71 which is formed by the beveling of the edges of the dodecahedron1 and developing these new faces to the exclusion of the dodecahedron faces4 ,combinations of the dodecahedron and trapezohedron 7#cf faces7 may occur4 ,all the garnets have a hardness of #g to #g4e1 and the specific gravity runs from #c4b to #d4c1 according to the composition4 ,in size they run from as small as a grain of sand up to as large as a boy's marble1 and occasionally even to four inches in diameter4 ,the color varies with the composition1 from colorless to yellow1 red1 violet1 or green4 ,there is no cleavage1 and the luster is always vitreous4 ,garnets are usually accessory minerals1 found in metamorphic rocks1 though they are sometimes also present in granites and lavas4 ,they are always segregations which have taken place in the presence of high temperatures4 ,when clear and perfect several of the garnets are used as gems4 ,on the other hand some of the common garnets occur in such quantities that they are crushed and used as abrasives1 for such work as dental polishes1 or for leather and wood polishing4 ,the following is the composition of some of the commoner garnets4 ,ca,al7,si,o7 grossularite ,mg,al7,si,o7 pyrope ,fe,al7,si,o7 almandite ,mn,al7,si,o7 spessartite ,ca,fe7,si,o7 andradite ,ca,cr7,si,o7 uvarovite ,grossularite is chiefly found in crystalline limestones1 which have resulted either from contact with lavas1 or from general metamorphism of impure limestones4 ,these garnets are colorless to white1 or more often shades of yellow1 orange1 pink1 green or brown1 according to traces of impurity which they may contain4 ,the cinnamon-colored variety from ,ceylon is termed cinnamon stone1 and is a fairly popular gem4 ,pyrope is a deep-red color and when perfect is highly prized as a gem4 ,it is found in dark-colored igneous rocks1 like lavas1 or serpentines4 ,some of the finest come from ,south ,africa1 where they are found in company with the diamond4 ,almandite is dark-red to brown in color1 the brownish-cast distinguishing it from pyrope4 ,it is one of the garnets known as 8common garnet40 ,in some cases it is clear and deep colored enough to be used as a gem1 but mostly it is muddy in appearance4 ,the name almandite comes from ,alabanda1 a city of the ancient district of ,caria1 ,asia ,minor1 whence garnets were traded to ancient ,rome4 ,the finest garnets 8,sirian garnets0 came from the city of 8,sirian0 in ,lower ,burma1 and were supposed to have been found near there1 but careful investigation shows that no garnets occurred near there1 and this town was therefore1 even at that early time1 a distributing point for garnets1 found probably further to the east4 ,the 8,sirian0 garnet had a violet cast and now the term is used to indicate a type of garnet1 rather than a locality4 ,spessartite is dark-hyacinth-red1 or red with a violet-tinge1 and is one of the less-common garnets4 ,it is usually found in granites4 ,the finest garnets of the type come from ,amelia ,court ,house1 ,va41 which has yielded some ranging from one up to a hundred carats4 ,andradite is another garnet which is termed 8common garnet40 ,it is red in color1 but with a yellowish-cast which distinguishes it from almandite1 but these two are not easy to separate4 ,it is found mostly in metamorphosed limestones4 ,one variety is black in color and called malanite4 ,it is found in lavas4 ,the common yellowish-red garnets are found through ,new ,england and the ,piedmont ,plateau4 ,uvarovite is a rare garnet of emerald-green color1 found in association with chromium ores4 ,the number of localities for garnets is so great that a list would suggest most of the regions where metamorphic rocks occur1 as all over ,new ,england1 throughout the ,piedmont ,plateau1 the ,rocky ,mountains1 etc4 ,certain fine clear garnets1 found in ,montana1 northeastern ,arizona1 and northwestern ,new ,mexico are sold under the trade name of 8,montana1 ,arizona or ,new ,mexico rubies40 ,these are of fine quality and are mostly collected by the ,indians from the ant hills and scorpion's nests of those regions4 ,garnets are among the earliest stones mentioned in ancient languages1 as would be expected from the way these hard and beautiful crystals weather out of the much softer metamorphic rocks1 like schists4 ,in the past they1 with most any other translucent red stone1 were included under the name carbuncle4 ,this1 however1 is not the name of any mineral1 but refers rather to a mode of cutting1 en cabochon or with a convex surface4 ,glucinum ,glucinum is a rare metal1 silvery-white in color1 malleable1 and melting at a fairly low temperature4 ,it is found in the mineral beryl1 from which has come the alternative name beryllium4 ,the name comes from the sweet taste of its salts4 ,except for beryl its minerals are rare1 and the metal has found but few uses for man4 ,beryl ,gl,al7,si,o7 ,pl4 #ci ,occurs in hexagonal crystals in granites1 gneisses and mica schists2 hardness1 #g4e2 specific gravity1 #b4g2 color usually some tint of green2 luster vitreous2 transparent on thin edges4 ,when this mineral occurs in coarse hexagonal prisms1 with or without faces on the ends1 it is known as beryl2 when the crystals are clear and perfect and of a dark-green color1 they are of gem value and are termed emerald2 when of a light-green color1 they are aquamarine2 and when bright-yellow in color1 they are the golden beryl4 ,there is little difficulty in determining beryl1 for only apatite occurs in such crystals1 and is green1 and this latter mineral has a hardness of only #e4 ,there is an imperfect basal cleavage4 ,ordinary beryl is fairly common in granites of the pegmatite sort1 and less common in gneisses and mica-schists4 ,this type often furnishes crystals of large size1 up to two and three feet in diameter4 ,beryl which is free from cracks and inclosures1 so it can be used as a gem1 is so rare1 that the emerald has a value above that of the diamond1 and second only to the ruby4 ,it is one of the gems with a long history1 having been quarried on the west coast of the ,red ,sea at least #afej ,b4,c4 by the ,egyptians4 ,to early people it had a power to quicken the prophet instinct and made the wearer see more clearly4 ,the ,spanish conquistadores found fine emeralds among the treasures of both ,mexico and ,peru4 ,in the ,united ,states1 ,stony ,point1 ,n4 ,c41 was a notable locality for these gems1 but now seems to have been exhausted4 ,the name emerald has been applied to many other green stones1 usually with some geographical modification1 as 8,oriental emerald0 which is green corundum1 8,brazilian emerald0 which is tourmaline1 etc4 ,giant beryls have been found at ,acworth and ,grafton1 ,n4 ,h41 and at ,royalston1 ,mass4 ,localities for ordinary beryl are ,albany1 ,norway1 ,bethel1 ,hebron1 ,paris1 and ,topsham1 ,me41 ,barre1 ,goshen and ,chesterfield1 ,mass41 ,new ,milford and ,branchville1 ,conn41 ,chester and ,mineral ,hill1 ,penn41 ,stony ,point1 ,n4 ,c41 and many other localities in the ,appalachians2 also ,mount ,antero1 ,colo41 and in the ,black ,hills of ,south ,dakota4 ,sodalite ,na,al,cl7,si,o7 ,occurs in irregular masses1 sometimes in dodecahedrons2 hardness1 #e4e-f2 specific gravity1 #b4c2 color deep-blue to colorless2 streak white2 luster vitreous2 translucent on thin edges4 ,this striking mineral1 with its deep-blue to azure color1 is not easily confused with any other4 ,it is characteristic of soda-rich igneous rocks such as syenite and some lavas4 ,in this country it is found at ,litchfield1 ,me41 and ,salem1 ,mass4 ,zircon ,zr,si,o ,pl4 #ci ,usually occurs in tetrahedral crystals in igneous rocks2 hardness1 #g4e2 specific gravity1 #d4g2 color brown2 luster vitreous2 translucent on thin edges4 ,zircon1 the mineral of the rare earth element zirconium1 nearly always occurs in light-colored igneous rocks1 like syenite4 ,it may occur in schists or gneisses1 but in these rocks the crystals are of microscopic size4 ,because of their great hardness and insolubility1 zircon crystals resist weathering and are often found1 along with gold1 cassiterite1 or magnetite1 in sands which have resulted from the disintegration of syenite rocks4 ,zircon refracts and disperses light to a degree second only to the diamond1 so that clear crystals are sought as gems4 ,they are often called 8,matura diamonds0 because of their abundance at ,matura1 ,ceylon4 ,when the crystals are colorless or smoky they are termed jargons or jargoons2 when of a red-orange hue1 they are hyacinth or jacinth4 ,most of the zircon of gem-quality comes from ,ceylon1 where it is picked up as rolled-pebbles from the beds of brooks4 ,the most remarkable ,american locality for zircon is near ,green ,river1 in ,henderson ,co41 ,n4 ,c41 where it is found abundantly in a decomposed pegmatite dike1 from which many tons have been obtained4 ,it is also found at ,moriah1 ,warwick1 ,amity and ,diana1 ,n4 ,y41 at ,franklin ,furnace1 and ,trenton1 ,n4 ,j41 in the gold-bearing sands of ,california1 etc4 ,cyanite ,al,si,o ,pl4 #dj ,occurs in long blade-like crystals in gneisses and schists2 hardness1 #g at right angles to the length1 and #d4e parallel to the length2 specific gravity1 #c4f2 color blue2 luster vitreous2 translucent on thin edges4 ,there are only a few blue minerals1 and the way in which cyanite occurs in long thin blade-like crystals is entirely characteristic4 ,if more is still wanted to determine this mineral1 its unique character in having the great hardness #g when scratched parallel to the length1 and only #d4e when scratched crossways1 will settle any doubts4 ,the mineral sillimanite has the same composition as cyanite1 but is fibrous in habit and has the hardness #f4e4 ,if cyanite is heated to #acej ,c4 it changes its character and becomes sillimanite4 ,cyanite is found as an accessory mineral in metamorphic rocks1 such as gneiss and schist1 at ,chesterfield1 ,mass41 ,litchfield and ,oxford1 ,conn41 in ,chester ,co41 ,penn41 in ,north ,carolina1 etc4 ,the ,mica ,group ,the micas are very common minerals1 easily recognized by their very perfect basal cleavage1 as a result of which thin sheets1 often less than a thousandth of an inch in thickness1 readily split off4 ,these are tough and elastic1 which distinguishes mica from the chlorite group in which there is similar basal cleavage1 but the sheets are not elastic4 ,micas are complex silicates of aluminum1 with potassium1 iron1 lithium1 magnesium and hydrogen4 ,they are one of the principle components of many granites1 gneisses1 and schists4 ,this mineral is always crystalline1 being in the monoclinic system1 but occurring in six-sided prisms4 ,the cleavage is so dominant a character that the crystal form is usually overlooked1 as it is seldom requisite in determining this mineral4 ,the size of the sheets of mica depend on the size of the crystals1 the larger sheets expressing great slowness in cooling from the original magmas4 ,sometimes the crystals may be two or even three feet in diameter4 ,the hardness is not great1 ranging between #b and #c4 ,the specific gravity lies between #b4g and #c4b4 ,the color varies according to the composition1 from silvery-white1 through gray1 pink1 and green to black4 ,the luster is vitreous to pearly1 sometimes gleaming in the darker-colored varieties4 ,the commoner types of mica are as follows3 ,muscovite1 ,h,k,al7,si,o7 or potash mica4 ,lepidolite1 ,li,k7,al,,oh,f7,al7,si,o7 or lithia mica4 ,biotite1 7,,hk77,mg,fe7,al7,si,o7 or iron mica4 ,phlogopite1 ,h,k,mg,al7,si,o7 or magnesia mica4 ,muscovite is colorless1 silvery-white1 gray or sometimes pale-green or brown4 ,it gets its name from ,moscow where it was early used for window panes1 and it is still used for stove and furnace doors1 as well as in electric work1 for a lubricant1 etc4 ,the best crystals occur in granites1 in the coarse varieties of which large crystals may be obtained4 ,it is found also as small scales in gneisses and schists1 and when weathered from its original rocks it may be present in sandstones and shales4 ,muscovite is always in its origin an elementary component of deep-seated igneous rocks1 like granite2 but is never a component of extruded lavas4 ,sericite is muscovite which has been secondarily produced by the alteration of other minerals into muscovite1 as when feldspar1 cyanite1 topaz1 etc41 have been modified by the presence of heat and hot vapors1 when near lavas that have come in contact with other rocks4 ,muscovite is very resistant to alteration by weathering1 but when it does change1 the greater part of it becomes kaolin4 ,it is found at ,acworth and ,grafton1 ,n4 ,h41 in plates1 sometimes a yard across at ,paris1 ,me41 ,chesterfield and ,goshen1 ,mass41 ,portland and ,middletown1 ,conn41 at ,warwick1 ,edenville1 etc41 ,n4 ,y41 and all down the ,appalachian ,mts41 also in the ,rocky ,mts41 the ,cascade ,range1 etc4 ,lepidolite is pink or lilac in color and occurs in scaly masses1 mostly in granites4 ,it does not come in large crystals4 ,lepidolite is found at ,paris and ,hebron1 ,me41 ,middletown1 ,conn41 ,pala1 ,calif41 etc4 ,biotite is dark-brown or black mica4 ,like muscovite it is very common1 making one of the chief components of granites1 gneisses and schists2 and1 unlike muscovite1 it may occur in extrusive lavas1 like trachyte1 andesite1 and basalt4 ,it resists weathering much less than muscovite1 so that1 when the rocks of which it is a component disintegrate1 biotite is usually altered to kaolin and other compounds4 ,it is likely to occur in good-sized crystals1 especially at ,topsam1 ,me41 ,moriah1 ,n4 ,y41 ,easton1 ,penn41 etc4 ,phlogopite is pale-brown1 often coppery in color1 and is most likely to occur in serpentines1 or crystalline limestones or dolomites1 often in fine crystals1 of good size4 ,while one of the less abundant micas1 this is found at ,gouverneur1 ,edwards1 and ,warwick1 ,n4 ,y41 ,newton1 ,n4 ,j41 and ,burgess1 ,canada4 ,topaz ,al,f,si,o ,pl4 #da ,occurs in crystals mostly2 hardness1 #h2 specific gravity1 #c4e2 colorless to pale-yellow2 luster vitreous2 transparent on thin edges4 ,topaz may be colorless1 but is more often some shade of yellow1 and at times brown or even blue4 ,its hardness is characteristic1 there being but few minerals as hard1 and it is used to represent the hardness #h in the ,moh's scale4 ,the crystals are orthorhombic prisms1 with the edges of the prism beveled and often striated4 ,the ends of crystals usually terminate with a basal plane1 parallel to which there is good cleavage4 ,between this basal plane and the prism faces there are usually several sets of small faces as indicated on ,plate #da4 ,this mineral1 as is also true of most minerals containing fluorine1 is one of those which have crystallized out from hot vapors1 escaping from igneous magmas4 ,it is associated with such minerals1 as tourmaline1 beryl1 fluorite1 and cassiterite1 and occurs mostly in cavities or seams1 in or near granites4 ,ordinary topaz1 which means crystals that are imperfect by reason of tiny cracks and impurities is not very rare1 but crystals which are perfect and clear in color are considered gems4 ,most of the gem-topaz is some shade of yellow1 but may be brown or blue1 never1 however1 pink1 as is often seen in jewelry4 ,the 8pinking0 is artificial1 and done by packing yellow or brown topaz in magnesia1 asbestos1 or lime1 and then heating it slowly to red heat1 after which it is cooled slowly4 ,if underheated the color is salmon1 if overheated all color disappears4 ,topaz has been a gem for centuries1 the earliest records coming from ,egypt4 ,the name comes from topazios1 meaning to seek1 because the earliest known locality1 from which it was gathered1 was a little island of that name in the ,red ,sea1 and this island was often surrounded by fog and hard for those early mariners to find4 ,here by mandate of the ,egyptian kings the inhabitants had to collect topazes1 and deliver them to the gem-cutters of ,egypt for polishing4 ,several yellow stones are called topaz1 as the 8,oriental topaz0 which is corundum and more valuable than topaz itself2 and several varieties of yellow quartz1 which go under such names as 8,saxon10 8,scotch10 8,spanish10 and 8smoky0 topaz4 ,when topaz occurs colorless as in ,siberia1 the ,ural ,mountains1 and in the state of ,minas ,geraes1 ,brazil1 in all of which places it is found as pebbles in brooks1 it goes under the name of 8slave's diamonds40 ,brazil is today the chief source of gem-quality topaz4 ,ordinary topaz is found in this country at ,trumbull1 ,conn41 ,crowder's ,mt41 ,n4 ,c41 ,thomas ,mts41 ,utah1 in ,colorado1 ,missouri1 and ,california1 etc4 ,staurolite ,fe,al,,oh7,si,o7 ,pl4 #da ,occurs in orthorhombic crystals2 hardness1 #g4e2 specific gravity1 #c4g2 color brown2 luster resinous2 translucent on thin edges4 ,this mineral occurs about equally abundantly in simple crystals similar to the outline on ,plate #da1 and in twins which have grown through each other either at #ij or at #fj4 ,the color is either brown or reddish-brown4 ,in all cases it is an accessory mineral1 occurring in metamorphic rocks1 usually schists1 though less frequently in slates and gneisses4 ,from the seventeenth century on1 it has been used as a baptismal stone1 and worn as a charm1 legends stating that it fell from the heavens4 ,fine crystals have been found in ,patrick ,county1 ,va41 and there is in this region the legend1 that when the fairies heard of the crucifixion of ,christ1 they wept and their tears falling crystallized in the form of crosses1 such as the one shown on ,plate #da4 ,staurolite is found in the schists of ,new ,england as at ,windham1 ,me41 or ,chesterfield1 ,mass41 and all down the east side of the ,appalachian ,mountains to ,georgia4 ,olivine 7,mg,fe7,si,o ,peridot or ,chrysolite ,occurs in grains and irregular masses in dark lavas2 hardness #f4e to #g2 specific gravity #c4c2 color bottle- to olive-green2 luster vitreous2 translucent on thin edges4 ,olivine rarely occurs in crystals1 but when it does they belong to the orthorhombic system4 ,the dark-green grains or masses are recognized by the color1 considerable hardness and indistinct cleavage4 ,serpentine may have a similar color1 but its hardness is only #d4 ,in hydrochloric acid olivine decomposes to a gelatinous mass4 ,olivine is typically one of the constituents of the dark lavas1 like basalt1 gabbro1 or peridotite4 ,it is also a common mineral in meteorites4 ,olivine1 in the presence of water1 alters to other minerals1 especially serpentine1 with great facility4 ,it occurs fairly widely wherever the dark lavas are present1 as in the ,white ,mountains of ,n4 ,h41 in ,loudoun ,co41 ,va41 in ,lancaster ,co41 ,penn41 and in many localities in the ,rocky ,mountains and ,cascade ,range4 ,epidote ,ca7,al,o,h77,al,fe77,si,o7 ,pl4 #db ,occurs in grains or columnar masses2 hardness1 #f4e2 specific gravity #c4d2 color green1 usually a pistachio or yellow-green2 luster vitreous2 translucent on thin edges4 ,rarely epidote occurs in crystals1 which belong to the monoclinic system1 and may be either short like the diagrams on plate #db or long and needle-like4 ,the color and hardness will suffice to determine this mineral1 as almost no other has the peculiar yellowish-green color which is characteristic of this form4 ,epidote occurs primarily in metamorphic rocks at or near the contact with igneous rocks2 or it may be a secondary mineral resulting from the weathering of granites1 especially along seams4 ,it sometimes occurs with hornblende in highly folded schists1 as in ,new ,york ,city4 ,it is often a mineral which has resulted from the alteration of other minerals1 as pyroxene1 amphibole1 biotite1 or even feldspars4 ,it is found at ,chester and ,athol1 ,mass41 ,haddam1 ,conn41 ,amity1 ,munroe and ,warwick1 ,n4,y41 ,east ,branch1 ,penn41 in the ,lake ,superior region1 in the ,rocky ,mountains1 etc4 ,tourmaline 7,fe,cr,na,k,li7,mg,b,al,h,si,o ,pl4 #db frontispiece ,occurs in three-sided prismatic crystals2 hardness1 #g2 specific gravity1 #c4a2 colorless1 red1 green1 brown1 or black2 luster vitreous2 transparent on thin edges4 ,tourmaline is readily distinguished from other minerals1 as it always occurs in long to short prisms1 which are three-sided in cross section4 ,there is also a tendency for the sides to be curved as seen on the end view of ,d1 ,pl4 #db4 ,frequently the vertical edges of the prism are beveled with one1 two or three faces1 grouped about each of the three original edges1 and there are often striations on the prism faces4 ,the ends are terminated by a low rhombohedron and again there may be a host of modifying faces on the edges and corners of the end4 ,the common varieties are brown or black in color1 but occasionally there may occur green1 red1 yellow or almost any color4 ,when the crystals are perfect1 that is free from impurities and without tiny cracks1 tourmaline becomes a gem of popularity and value4 ,tourmaline is very complex in composition and may vary considerably1 the sodium1 potassium1 lithium1 magnesium1 and iron being either more or less abundant or even lacking4 ,the color is to some extent dependent on the proportions of these elements present1 the dark varieties having more iron1 and the light colored tourmalines lacking it4 ,this mineral is one of those which form from superheated vapors1 escaping from molten magmas4 ,it will therefore occur in veins1 often associated with copper minerals1 in crystalline limestones1 or in cavities in granites1 where it is associated with such minerals1 as beryl1 apatite1 fluorite1 topaz1 etc4 ,if heated tourmaline crystals develop electricity1 with the effect of making one end a positive and the other a negative pole1 and then will attract bits of straw1 ashes1 etc4 ,it was first introduced into ,europe about #agjc from ,india1 and its vogue as a gem has greatly increased since it was found on ,mount ,mica near ,paris1 ,me4 ,this ,paris1 ,me41 locality was discovered by two boys1 amateur mineralogists1 ,elijah ,l4 ,hamlin and ,ezekiel ,holmes1 who in #ahbj were returning home from a trip hunting for minerals1 when1 at the root of a tree1 they discovered some gleaming green substance4 ,it proved to be gem-quality tourmaline4 ,a snow storm that night buried their 8claim10 but next spring it was visited and several fine crystals found4 ,later this locality was systematically worked1 and over #ej1jjj worth of tourmaline taken from the pegmatite seam in the granite1 which lay under the crystals found on the surface4 ,the figure in the frontispiece is one of the crystals from there4 ,well known localities are ,paris and ,hebron1 ,me41 ,goshen and ,chesterfield1 ,mass41 ,acworth and ,grafton1 ,n4 ,h41 ,haddam and ,munroe1 ,conn41 ,edenville and ,port ,henry1 ,n4 ,y41 ,jefferson ,co41 ,colo41 ,san ,diego ,co41 ,calif41 etc4 ,kaolinite ,h,al,si,o ,kaolin ,usually found in whitish clay-like masses2 hardness1 #b2 specific gravity1 #b4f2 color white to grayish or yellowish2 luster dull4 ,kaolinite does not generally occur in crystals1 though crystals of microscopic size and monoclinic forms have been found4 ,it is a secondary mineral resulting from the decomposition by weathering of feldspars1 the calcium1 potassium or sodium having been replaced by water4 ,when found in place it is generally white or nearly white1 and is characterized by its greasy feel4 ,as granites or other feldspar-bearing rocks are weathered away1 the kaolin is washed out by water1 and with other fine material is carried down into lakes or the sea1 where it settles to the bottom and is known as clay4 ,clay is kaolin with more or less impurities4 ,pure kaolin is used for the manufacture of china and white porcelain ware2 but when it is impure1 especially when it has iron in it1 baking causes the product to turn red or brown1 so that it is only suitable for making tile1 bricks1 etc4 ,it is found almost anywhere that feldspar rocks are1 or have been1 exposed to weathering4 ,talc ,h,mg7,si,o7 ,occurs in scales1 or in fibrous1 scaly or compact masses2 hardness1 #a2 specific gravity1 #b4g2 color white1 gray or pale-green2 luster pearly2 translucent on thin edges4 ,this mineral is as soft as any1 only graphite and molybdenite being of the same hardness1 but both these latter two have a black streak1 while the streak of talc is white4 ,the greasy feel is also characteristic4 ,talc is very seldom found in crystals1 but if they are found1 they will appear like flakes and have a hexagonal cross section1 though in reality they belong to the monoclinic system4 ,talc is a secondary mineral which usually results from the exposure of magnesium silicates1 such as pyroxenes or amphiboles1 to moisture4 ,in this case1 in-as-much as the original rocks were metamorphic in origin1 the talc therefrom will occur in old metamorphic regions4 ,some talc is also formed by the action of silica-bearing waters on dolomite4 ,this is likely to be the case near the contact between dolomite and igneous rocks4 ,talc is closely related to serpentine and likely to be found in the same regions4 ,talc has come to have a considerable use4 ,some of it is compact and then called soapstone1 and this was used by the ancient ,chinese to make images and ornaments2 and our ,north ,american ,indians used it to make large pots1 to serve as containers for liquids4 ,some of these pots have been carved out with great skill1 so as to be fairly light in proportion to what they would hold4 ,pipes and images were also carved from soapstone4 ,today we still cut soapstone into slabs to make mantels1 laundry tubs and sinks4 ,the scaly and fibrous varieties are ground1 and used in making paper1 paint1 roofing1 rubber1 soap1 crayons1 toilet powders1 etc4 ,the ,united ,states produce and use over half the world's production1 our industries requiring over #ajj1jjj tons of talc a year4 ,of this #ch goes into paper1 #bc into paint1 #ah into roofing1 and so on down to toilet powder which uses #b1 or #b1ejj tons a year4 ,talc is found in metamorphosed regions1 that is in ,new ,england1 all down the east side of the ,appalachian ,mts41 in the ,rocky ,mts41 and the ,cascade ,ranges1 with a large number of local occurrences4 ,new ,york ,state is the leading producer4 ,serpentine ,h,mg,si,o ,pl4 #dc ,occurs in compact1 granular or fibrous masses2 hardness1 #c2 specific gravity1 #b4f2 color green2 luster greasy2 translucent on thin edges4 ,serpentine is never in crystals4 ,its color and hardness serve to distinguish it4 ,like talc it is a secondary mineral resulting from the alteration1 in the presence of moisture1 of pyroxenes1 amphiboles1 and especially1 olivine4 ,as these are often in metamorphic rocks1 the serpentine is likely to be associated with metamorphic rocks4 ,some serpentine is also the result of the action of silica-bearing water on dolomite1 and this is likely to occur in areas of sedimentary rocks4 ,the fibrous variety of serpentine1 chrysolite1 usually occurs in seams or veins1 and when the fibers are long1 it is used as asbestos4 ,this form of asbestos is the one most used commercially today1 as there are remarkably large deposits of it in the ,province of ,quebec1 which provide the major part of the world supply4 ,in the ,united ,states it is also found in ,california and ,arizona but only in moderate quantities4 ,massive serpentine is used in considerable quantities as an ornamental stone1 the green color varied with streaks and blotches of white1 yellow and red1 due to various impurities1 making it very effective4 ,it is1 however1 only suitable for interior work as the weather quickly spoils the polished surface4 ,this is further discussed under serpentine rock1 page #bde4 ,serpentine is found at ,newfane1 ,vt41 ,newburyport1 ,mass41 ,brewster1 ,antwerp1 etc41 ,n4 ,y41 ,hoboken1 ,n4 ,j41 in ,pennsylvania1 ,maryland1 etc4 ,chlorite ,h7,mg,fe7,al7,si,o7 ,pl4 #dc ,occurs in monoclinic crystals of six-sided outline1 or in scaly flakes or masses2 hardness1 #b2 specific gravity #b4h2 color green2 luster pearly on cleavage faces2 translucent on thin edges4 ,chlorite is a family name1 covering a series of closely related minerals1 so similar in appearance that they are best considered under this common name4 ,in many respects they resemble mica1 in the shape of the crystals and the remarkable basal cleavage4 ,at first glance it is easy to confuse the two1 but chlorite scales are not elastic1 and when bent1 stay bent1 instead of snapping back like mica4 ,in fact they look like more or less rotted micas4 ,this is more than appearance1 for chlorites form as a result of the alteration of micas in the presence of moisture4 ,they are then secondary1 and will be found where mica-rocks have been weathered1 as in granites and schists4 ,they may be expected anywhere that micas have been long exposed1 as in ,new ,england1 the ,rocky ,mountains1 or the ,sierra ,nevada or ,cascade ,ranges4 ,special localities are ,brewster1 ,n4 ,y41 ,unionville and ,texas1 ,penn41 etc4 ,the ,zeolites ,the zeolites are a group of white minerals1 with a pearly luster1 light weight1 and easy solubility in acids2 which1 because their contained water is lightly held1 readily boil before the blowpipe4 ,they are all secondary minerals1 which result from the decomposition of feldspars1 when exposed to weathering4 ,they are almost universally found in seams and cavities of disintegrating lavas4 ,from a group of a dozen or so1 three are common enough to be considered here4 ,they may be found by watching such places1 as where trap rock is being quarried for road material1 or being blasted for any reason4 ,analcite ,na,al,si,o #b;,h,o ,pl4 #dd ,occurs as trapezohedrons in seams and cavities in lavas2 hardness1 #e4e2 specific gravity1 #b4b2 colorless1 white or pink2 luster vitreous2 transparent on thin edges4 ,analcite usually occurs in the #bd-sided form1 known as a trapezohedron1 as illustrated in figure ,a1 ,pl4 #dd2 but it may also occur in cubes with the three faces of the trapezohedron on each corner4 ,small crystals are often colorless1 but the larger ones are either white or pink1 and are opaque4 ,while the form is the same as that of garnets1 the color1 lesser hardness1 and the occurrence in lavas will serve to distinguish this mineral4 ,if placed in hydrochloric acid analcite dissolves to a gelatinous mass4 ,it is always found in seams and cavities in lavas1 as at ,bergen ,hill and ,weehawken1 ,n4 ,j41 ,westfield1 ,mass41 in the ,lake ,superior region1 etc4 ,natrolite ,na,al,si,o #b;,h,o ,plate #dd ,occurs as bristling crystals in seams and cavities in lavas2 hardness1 #e4e2 specific gravity1 #b4b2 colorless2 luster vitreous2 transparent on thin edges4 ,natrolite occurs as beautiful bristling tufts of needle-like crystals1 each crystal an orthorhombic prism with a very low pyramid on the end4 ,this mineral is so easily fusible that it can be melted in a candle flame1 giving to the flame the characteristic yellow color due to sodium4 ,in hydrochloric acid it dissolves to a gelatinous mass4 ,it is always a secondary mineral in cavities and seams in disintegrating lavas1 and the tuft-like manner of growth is so characteristic1 that once seen1 it will always be recognized4 ,natrolite is found at ,weehawken and ,bergen ,hill1 ,n4 ,j41 at ,westfield1 ,mass41 in the ,lake ,superior region1 etc4 ,stilbite ,h7,ca,na7,al7,si,o7 #d;,h,o ,pl4 #dd ,usually occurs in sheaf-like bundles of fibrous crystals2 hardness1 #e4e2 specific gravity #b4b2 colorless to white1 yellow or brown2 luster vitreous2 transparent on thin edges4 ,stilbite crystals are really monoclinic1 but on account of almost universal twinning1 appear as if orthorhombic4 ,like the two foregoing minerals1 stilbite is found in the seams and cavities of disintegrating lavas4 ,it is readily recognized by its habit of forming in sheaf-like bundles of fibrous crystals4 ,it may also1 but more rarely1 occur in radiating masses4 ,in hydrochloric acid it is completely dissolved4 ,it is found in lavas1 at ,weehawken and ,bergen ,hill1 ,n4 ,j41 in the ,lake ,superior region1 etc4 ,calcium ,calcium is one of the most abundant of metals1 but never occurs as such in nature1 nor is it used as a metal by man4 ,in its metallic form it is yellowish-white1 and intermediate between lead and gold in hardness4 ,exposed to air it soon tarnishes by oxidation1 and in water rapidly decomposes the water1 forming the oxide4 ,however1 it has a great affinity for other elements1 and makes a large number of minerals1 the most important of which are calcite1 aragonite1 gypsum and fluorite1 while it is an essential component of some garnets1 anorthite1 epidote1 amphibole and pyroxene4 ,it is very widely distributed as limestone1 and is found in solution in most all natural waters1 and in the shells and bones of many animals and some plants4 ,calcite ,ca,c,o ,pl4 #de ,occurs in well defined crystals in incrustations1 and in stalactitic1 oolitic1 and granular masses2 hardness1 #c2 specific gravity #b4g2 colorless to white1 or when impure1 yellow1 brown1 green1 red or blue2 luster vitreous to dull2 transparent on thin edges4 ,next to quartz1 calcite is the most abundant of all minerals1 and occurs in an almost endless variety of forms1 over #cjj having been described4 ,it belongs to the hemihedral section of the hexagonal system1 the form of the crystals being all sorts of variations of the rhombohedron1 and combinations of left and right handed rhombohedrons4 ,the cleavage is entirely uniform1 in three directions1 parallel to the faces of the rhombohedron1 and at an angle of #gd #ee with each other4 ,crystals may occur in the form characteristic of the cleavage1 but not often4 ,the commonest forms are a more or less elongated scalenohedron1 made by combining right and left handed rhombohedrons1 so that the resulting pyramid is six-sided1 as in figure ,c1 ,plate #de4 ,such a scalenohedron may be combined with other forms in a great variety of ways4 ,the six-sided prism with the ends terminated by one or more sets of rhombohedral faces is also fairly common4 ,twinning occurs occasionally4 ,the quickest way to determine calcite is by the hardness 7#c71 combined with the fact that it effervesces1 when hydrochloric acid is dropped upon it4 ,an interesting feature of this mineral is its marked property of deflecting light rays1 so that a line or object placed behind a piece of clear calcite appears double4 ,it was with pieces of calcite from ,iceland that this was first seen2 so that large transparent crystals of calcite are still called ,iceland spar2 and such calcite is used to make the ,nichol's prisms for microscopes1 which are so useful in the study of minerals4 ,this power of refracting light is present in all minerals1 but not to such a marked degree as in calcite4 ,the elongated scalenohedrons of calcite are often called 8dog-toothed spar0 from a fancied resemblance between them and the dog's tooth4 ,calcite is present in solution in the water of the sea and most streams1 from which it is withdrawn by many animals and some plants1 to make their shells1 and bones4 ,the foraminifera1 some sponges1 the echinoderms1 corals and molluscs all draw large quantities from the water in which they live1 and build more or less permanent structures from it4 ,these shells when they fall to the bottom1 or after being broken to bits1 accumulate on the bottom and make limestone1 which is widely distributed over the country4 ,this same limestone1 when metamorphosed and crystalline1 is marble4 ,calcite then is readily soluble in water1 and streams flowing along crevices and fissures in limestone dissolve out great cavities or caves1 like the ,mammoth ,cave of ,kentucky4 ,other water1 percolating through the limestone1 comes to these cavities saturated with lime in solution and drips from the roofs and walls2 then as part of the water evaporates1 it deposits part of its lime in icicle-like masses1 hanging from the roof4 ,such masses of non-crystalline calcite are called stalactites4 ,below on the floor of the cave1 conical masses are built up in the same manner where the dripping water falls on the floor4 ,these are stalagmites4 ,in these limestone caves and in smaller cavities many of the most beautiful crystals grow4 ,somewhat similarly1 when hot water from deep springs comes to the surface1 it cools and can not carry as much lime1 and so around the spring is laid down layer after layer of non-crystalline calcite making a mass known as travertine4 ,sometimes this is colored by iron or other impurities and a banded effect results4 ,such travertine as the 8,suisun marble0 from ,california1 8,california onyx10 8,mexican onyx10 and 8satin spar0 all belong to this class4 ,the coral animals1 especially in tropical waters precipitate an enormous amount of lime1 until whole reefs are built of lime in this non-crystalline form4 ,in places it is hundreds of feet thick and hundreds of miles in extent4 ,some of this coral has become popular for personal adornment4 ,this is particularly a small1 fine-grained variety1 ,corallum rubrum1 which lives almost exclusively in the ,mediterranean ,sea4 ,this coral is red in color1 varying all the way from a deep red to white4 ,it grows in small masses1 three pounds being a good sized mass1 in water #fj to #ajj feet deep1 requires some ten years to develop a full-sized mass4 ,the making of this into beads and ornaments is an ,italian industry4 ,the demand is growing1 while at the same time the supply is diminishing1 and search is being widely made for more such coral1 but up to the present time with little success4 ,this precious coral is much worn as a protection against the 8evil eye0 and is widely imitated1 apparently with as much protection to the wearer4 ,when coral beads are offered cheap1 they are probably something else1 red gypsum being much used4 ,this and all imitations can be readily detected by trying a drop of acid in the bead4 ,coral will effervesce1 but gypsum and other substitutes will not4 ,the bulk of the shells of most molluscs is made of lime1 but the mother-of-pearl layer inside is usually aragonite4 ,the chalk of the cliffs on either side of the ,english channel is lime1 and composed of the shells of single celled animals4 ,see p4 #bac4 ,when lime is deposited in loose porous masses1 as around grass1 etc41 and below hot springs1 this mass is termed calcareous tufa4 ,calcite will be found almost everywhere1 some of the localities for the finest crystals being ,antwerp and ,lockport1 ,n4 ,y41 ,middletown1 ,conn41 the caves of ,kentucky1 ,warsaw1 ,ill41 ,joplin1 ,mo41 ,hazel ,green1 ,wis41 etc4 ,aragonite ,ca,c,o ,pl4 #df ,occurs in crystals1 in columnar or fibrous masses1 or incrustations2 hardness1 #c4e2 specific gravity1 #b4i2 colorless1 white or amber2 luster vitreous2 transparent on thin edges4 ,aragonite has the same chemical composition as calcite1 but it crystallizes in the orthorhombic system1 either in simple forms like ,a on ,plate #df1 or twinned1 so as to make forms which seem hexagonal4 ,when in simple crystals its form easily distinguishes it from calcite and dolomite1 but when twinned it appears much like either of these two minerals4 ,from calcite it can then be distinguished by its greater hardness and the fact that it has cleavage in one direction only1 and that imperfect4 ,the cleavage is the only easy method of distinguishing it from dolomite4 ,however1 aragonite is most always easily distinguished by its habits1 for it generally forms long slender crystals1 which appear more like fibers than crystals4 ,neither calcite nor dolomite is at all fibrous4 ,aragonite is much less abundant than calcite1 and has resulted1 either from deposition from hot waters1 or from waters having sulphates in solution as well as lime4 ,much of the travertine1 and many stalagmites and stalactites are composed of aragonites1 forming as outlined under calcite4 ,the mother-of-pearl layer in the shells of bivalves is generally aragonite4 ,the pearly luster of this layer is due to its being formed by the successive deposition of one thin layer upon another2 so that light falling on the mother-of-pearl1 penetrates1 part of it to one layer and part to another1 and is then reflected4 ,certain molluscs have this layer composed of especially thin layers1 one1 the ,unios or freshwater clams1 the other1 the 8pearl oysters0 or ,aviculid1 these latter1 however1 being only distantly related to the edible oysters4 ,in the cases1 where molluscs of either of these two families are of large size1 large pieces of mother-of-pearl can be recovered1 and are used for buttons1 handles1 and various ornamental objects4 ,a further peculiarity of these same molluscs is the formation of pearls in the sheet of flesh1 lining the shells4 ,the pearls are round or rounded concretions of aragonite4 ,at the center there is a grain of sand1 or more often a tiny dead parasite4 ,either was an irritant to the mollusc1 and to be rid of it1 a layer of aragonite was secreted around it4 ,then as the mollusc continued to grow and secrete layers for its shell1 it also added each time another layer around the sand-grain or parasite1 until in time a pearl of noticeable1 and then of considerable size resulted4 ,these have all the pearly luster of the mother-of-pearl in a sphere which tends to make the luster even more marked4 ,pearls were in use as ornaments in ,china some twenty-three centuries before ,christ1 and in ,india over #ejj ,b4,c4 ,they were very highly prized by the ,romans and since their times the rulers of ,india have shown a remarkable fondness for them4 ,today the finest come from the ,gulf of ,persia and the ,red ,sea1 while still others are found about ,australia and in the ,caribbean ,sea4 ,in the ,united ,states not a few are collected every year from the fresh water clams1 some of them beautifully tinted with pink or yellow4 ,aragonite is found widely1 as at ,haddam1 ,conn41 ,edenville1 ,n4 ,y41 ,hoboken1 ,n4 ,j41 ,new ,garden1 ,penn41 ,warsaw1 ,ill41 etc4 ,anhydrite ,ca,s,o ,pl4 #df ,occurs in cleavable or granular masses1 rarely in crystals2 hardness1 #c-c4e2 specific gravity1 #b4i2 color white1 gray1 bluish or reddish2 luster pearly on cleavage faces2 transparent on thin edges4 ,when anhydrite occurs in crystals1 they are orthorhombic1 like the diagram on ,plate #df4 ,usually1 however1 it is found in beds or layers1 which were deposited by the evaporation of sea water1 and so it is associated with salt4 ,anhydrite has three cleavage planes which are at right angles to one another1 which produce rectangular or cube-like forms4 ,mostly anhydrite is associated with gypsum1 from which it differs by its greater hardness1 pseudo-cubic cleavage1 and the fact that anhydrite is not readily soluble in acid1 while gypsum is4 ,chemically it differs from gypsum in not having water of crystallization1 which gypsum does have4 ,the anhydrite is likely to occur as veins and irregular masses in beds of gypsum4 ,calcium sulphate is precipitated from sea water when #cg of the water has been evaporated1 and it may be deposited either as anhydrite or as gypsum1 the factors1 which decide as to which of these two minerals it will be1 being as yet unknown4 ,after deposition1 if exposed to moisture1 the anhydrite may change to gypsum1 irregular masses often remaining unchanged4 ,it is found in salt mines in ,elsworth ,co41 ,kan41 in limestone cavities at ,lockport1 ,n4 ,y41 in veins in ,shasta ,co41 ,calif41 etc4 ,gypsum ,ca,s,o #b;,h,o ,pl4 #dg ,occurs in crystals1 in cleavable masses1 or in fibrous masses2 hardness1 #b2 specific gravity1 #b4c2 colorless1 white1 amber1 gray1 or pink2 luster vitreous1 silky or pearly2 transparent on thin edges4 ,gypsum crystals are monoclinic as seen on ,plate #dg1 the perfect ones usually occurring in clay1 as at ,oxford1 ,o41 or in cavities2 while crystals of less perfect outline1 but with fine cleavages1 are found in ,utah1 ,kansas1 and ,colorado4 ,the cleavage is very perfect in one direction1 making it possible to strip off thin sheets almost like mica1 and less perfect in two other directions1 which appear on the smooth surface of the first cleavage as lines intersecting at #ff #ad4 ,twinning is also common in such a way1 that the two united crystals make forms similar to arrowheads4 ,these cleavages and the twinning show nicely in the photograph of gypsum on ,plate #dg4 ,gypsum is distinguished from anhydrite by its lesser hardness1 its cleavage and by being soluble in acids4 ,most gypsum occurs in beds or granular masses which were deposited from evaporating sea-water1 coming down when #cg of the water was lost4 ,such beds are often very extensive and are quarried as a source of gypsum to make plaster of ,paris1 stucco1 neat plaster1 ,keene's cement1 plaster and wall board1 partition tiles1 etc4 ,the use of the gypsum for plaster of ,paris and all these other uses is based on its affinity for water of crystallization4 ,the gypsum is first heated to about #djj ,c41 which drives off the water of crystallization1 and causes it to crumble to a powder1 which is the plaster of ,paris4 ,when water is added1 it is taken up and the powder 8sets10 or recrystallizes back to gypsum4 ,this simple reaction has made it very useful1 for making moulds1 casts1 hard finish on walls1 as stucco1 etc4 ,when the granular type of gypsum is fine grained1 it is known as alabaster1 which is used for carving vases1 statuettes1 ornaments1 etc4 ,the fibrous variety is called satin spar1 and is sometimes used for cheap jewelry and ornaments1 but it is very soft and quickly wears out4 ,at ,niagara ,falls there is a considerable trade in objects carved from this satin spar1 tourists buying them on the assumption that the mineral is native and comes from under the falls4 ,most of it1 however1 comes from ,wales1 the small amount of gypsum of that region being mostly granular4 ,gypsum is found all across the ,united ,states1 as in ,new ,york1 ,michigan1 ,virginia1 ,ohio1 ,alabama1 ,south ,dakota1 ,wyoming1 ,colorado1 ,utah1 ,california1 etc4 ,the ,strontium ,group ,strontium is a pale-yellow metal1 ductile and malleable1 but oxidizing quickly when exposed to the air4 ,it does not occur in its native state in ,nature1 but always as some compound1 usually either the carbonate or sulphate4 ,it resembles barium1 but differs in giving to the flame a brilliant red color1 on which account the compounds of strontium are used mostly in making red fire in fireworks4 ,strontianite ,sr,c,o ,occurs in needle-like crystals1 or in columnar or fibrous masses2 hardness1 #c4e-d2 specific gravity1 #c4f2 color white1 pale-green or pale shades of yellow2 luster vitreous2 transparent on thin edges4 ,strontianite is orthorhombic1 but appears as if hexagonal1 since its general habit is to have three twin crystals grow together in such a way as to make a six-sided double pyramid4 ,in this it is very like witherite1 both these minerals appearing externally much alike4 ,they can be readily distinguished1 however1 by holding a piece in the flame4 ,if it gives a red color to the flame it is strontianite1 if green1 it is witherite4 ,it effervesces readily in hydrochloric acid4 ,strontianite is found in veins and cavities in limestone1 where it has been deposited after being leached from the limestone by percolating waters4 ,though known at several localities it is not now being mined in this country1 what we use being imported mostly from ,germany4 ,it is found at ,schoharie1 ,chaumont ,bay and ,theresa1 ,n4 ,y41 in ,mifflin ,co41 ,penn41 etc4 ,celestite ,sr,s,o ,occurs in crystals1 cleavable masses and fibrous2 hardness1 #c2 specific gravity1 #c4i2 colorless1 white1 pale-blue1 or reddish2 luster vitreous2 transparent on thin edges4 ,celestite1 the sulphate of strontium1 is very like barite in external appearance and habit4 ,it is orthorhombic and occurs in tabular crystals4 ,its cleavage is perfect on the basal plane1 and imperfect in one other direction4 ,the ready way of distinguishing celestite from barite is to hold a piece in the flame4 ,if it is celestite it will color the flame red1 if barite1 green4 ,celestite is mostly found in veins or cavities in limestone1 where it has been deposited by percolating waters1 after having been leached from the limestone4 ,some years ago an important deposit of celestite was found on ,strontian ,island in ,lake ,erie1 but that was soon worked out and now no veins are being worked in this country4 ,it is also found at ,chaumont ,bay1 ,schoharie and ,lockport1 ,n4 ,y41 in ,kansas1 ,texas1 ,west ,virginia1 ,tennessee1 etc4 ,the ,barium ,group ,barium is another metal which does not occur in its native state in ,nature4 ,it has only been isolated as a yellow powder1 which1 exposed to air or water1 soon changes to one of the oxides4 ,both barium and its compounds are peculiar in causing a green color1 whenever exposed to the flame4 ,two of its compounds are fairly abundant1 the sulphate1 barite1 and the carbonate1 witherite4 ,the former is the more abundant and has come to be fairly widely used1 something over #ajj1jjj tons being annually consumed in the ,united ,states1 to make the body in flat finish paints for interior work and light colors1 for a filler in rubber goods1 linoleum1 oil cloth1 glazed paper1 and for a wide range of chemical compounds4 ,barite ,ba,s,o ,pl4 #dh heavy spar ,occurs in crystals or in lamellar1 nodular or granular masses2 hardness #c2 specific gravity1 #d4e2 colorless1 white or almost any color2 luster vitreous2 transparent on thin edges4 ,barite occurs in orthorhombic crystals1 which are tabular in form1 and usually have the edges beveled1 as in figure ,a1 ,plate #dh4 ,there is cleavage in three directions1 a rather perfect basal cleavage1 and two less perfect cleavages1 which are at right angles to the basal cleavage plane1 and intersect each other at #gh4 ,the tabular form1 the cleavage1 the heavy weight1 and the fact that a piece of barite put into the flame colors it green1 all serve to distinguish this mineral4 ,barite is a secondary mineral of aqueous origin1 which has been deposited in veins and cavities in igneous1 metamorphic1 or sometimes sedimentary rocks4 ,it is most likely to occur in veins in igneous or metamorphic rocks1 the barium having been dissolved from certain feldspars and micas by percolating water1 and then redeposited in the fissures1 as the water came into them4 ,if in sedimentary rocks1 the barite veins are usually in limestones4 ,barite is quite likely to be a gangue mineral for the ores of lead4 ,it is found at ,hatfield and ,leverett1 ,mass41 ,cheshire1 ,conn41 ,pillar ,point1 ,n4 ,y41 ,cartersville1 ,ga41 in ,virginia1 ,north ,carolina1 ,south ,carolina1 ,missouri1 ,kentucky1 ,tennessee1 ,alabama1 ,illinois1 ,wisconsin1 ,nevada1 ,california1 ,alaska1 etc4 ,witherite ,ba,c,o ,pl4 #dh ,occurs in crystals1 or in granular or columnar masses2 hardness1 #c4e2 specific gravity1 #d4c2 color white to gray2 luster vitreous2 translucent on thin edges4 ,witherite is not an abundant mineral4 ,its crystals are really orthorhombic1 but they are usually twinned1 three crystals growing through each other in such a manner that the resulting crystal appears like a six-sided double pyramid1 similar to the one figured on ,plate #dh4 ,the commonest mode of occurrence is in compact masses4 ,witherite effervesces when cold acid is dropped upon it1 which1 with its heavy weight1 and the green color it gives to the flame1 serves to distinguish the mineral4 ,it is used for medicines1 in chemical industries1 and a considerable amount is made into rat poisons4 ,the chief locality for witherite is in northern ,england1 but in this country it is found along with barite1 especially at ,lexington1 ,ky41 and in ,michigan4 ,carbon ,carbon is an element widely distributed in nature1 occasionally appearing in its elementary form1 as graphite or the diamond1 but much more important in its compounds4 ,small quantities are present in the air as carbon dioxide1 ,,co1 immense quantities occurring in the carbonate minerals1 which have been considered under their respective metallic salts1 as calcite1 malachite1 siderite1 cerrusite1 smithsonite1 witherite1 etc41 and still other large quantities being represented in organic compounds1 which occur as rocks under the heads of petroleum1 coal1 etc4 ,the occurrence of limestones1 graphite1 coal or petroleum is always indicative of the activity of living organisms1 and in some cases is the only indication of life in the earlier rocks4 ,graphite ,c ,plumbago ,occurs in hexagonal scales or flakes1 in layered masses1 or earthy lumps2 hardness1 #a2 specific gravity1 #b4a2 color black or steel-gray2 streak gray2 luster metallic2 opaque on thin edges4 ,like the diamond graphite is pure carbon1 but in this case it is in non-crystalline form4 ,it occurs in both igneous and metamorphic rocks4 ,in the former case it is either in flakes in the rock1 or in veins1 and has been derived directly from the molten magmas1 having either precipitated in the hardening granite or lava1 or having been carried into the fissures and there precipitated to make the veins of graphite4 ,in either case the graphite probably represents organic deposits which have been melted into the igneous magma at the time of its formation4 ,graphite may also occur in metamorphic rocks1 beds of coal or other organic deposits being altered by the heat4 ,such beds are often of considerable extent and economic importance4 ,the extreme softness1 greasy feel1 and the dark-gray streak readily distinguish graphite4 ,it is widely used in making crucibles and furnace linings for foundries1 lead pencils1 paint1 lubricating powders1 etc4 ,graphite is found at ,brandon1 ,vt41 ,sturbridge1 ,mass41 ,ashford1 ,conn41 in ,essex1 ,warren and ,washington ,cos41 ,n4 ,y41 ,clay1 ,chilton and ,coosa ,cos41 ,ala41 ,raton1 ,n4 ,m41 ,dillon1 ,mont41 etc4 ,diamond ,c ,occurs in octahedral crystals2 hardness1 #aj2 specific gravity1 #c4e2 colorless to yellow1 brown1 blue1 etc41 luster adamantine2 transparent on thin edges4 ,like graphite the diamond is pure carbon1 but in this case in crystal form4 ,it is the hardest of all minerals1 and as brilliant as any2 so that in spite of being by no means the rarest1 it may easily be considered the most popular of all gems4 ,tiny diamonds have been made artificially under great heat and pressure2 so that this mineral is thought of as forming in ,nature in dark igneous lavas at great depths4 ,the diamond has good cleavage parallel to the octahedron faces1 and1 in spite of some traditions to the contrary1 is brittle4 ,there are not many diamond localities1 the most famous being the ,kimberley district of ,south ,africa1 which produces many times as many diamonds as all the others put together1 though all the time some are being found in ,borneo and ,brazil4 ,a very few have been found in the ,united ,states1 only one locality however yielding them in the original matrix4 ,that is at ,murfreesboro1 ,ark41 where they are mined in a disintegrating peridotite 7a dark lava1 mostly peridot71 which has been extruded through the sedimentary rocks of that region4 ,this matrix is similar to the 8blue earth10 the matrix of the diamonds of ,south ,africa1 which occurs in 8pipes10 representing the necks of ancient volcanoes4 ,the ,american diamonds are of small size1 averaging considerably less than a third of a carat in weight1 which does not allow great value to the individual diamonds4 ,from time to time1 especially large diamonds have been found in different parts of the world1 the largest being the ,cullinan diamond1 found at the ,premier ,diamond ,mine of ,south ,africa4 ,it weighed #cjbe carats or about a pound and a quarter1 and was valued at over #c1jjj1jjj4 ,it was presented to ,king ,edward ,,vii1 who had it cut into #aa brilliants1 four of which are larger than any other diamond yet found4 ,other famous diamonds1 like the ,kohinoor1 #ajf carats1 found in ,india in #acjd2 the ,regent1 #acf carats1 also found in ,india2 the ,orloff1 #aic carats1 set in the eye of an ,indian idol2 the ,south ,star1 #abe carats1 the largest ever found in ,brazil2 the blue ,hope1 etc41 have in many cases romantic and interesting stories woven about them4 ,though for ages diamonds have been highly prized gems1 it is only in comparatively recent times that cutting and polishing have been resorted to1 for the purpose of enhancing their brilliancy4 ,this is done by grinding reflecting faces on the original stone1 by the aid of discs of iron or tin in which diamond dust has been embedded4 ,diamond chips and cloudy or imperfect diamonds are used for making tools for cutting glass1 rock drills1 etc4 ,phosphorus ,the element phosphorus at ordinary temperatures is an almost colorless1 faintly yellow1 solid substance of glistening appearance and waxy consistency4 ,in ,nature it does not occur pure1 but always as one of its compounds4 ,it is of great importance to man for it is one of the essentials for plant growth and also for the higher animals1 being required for the bones and to some extent for nervous tissue4 ,originally it is found in all the igneous rocks4 ,some of the phosphorus is removed by solution and carried to other regions and to the sea4 ,from this distribution it comes into the sedimentary rocks1 and1 when they are altered by heat1 into the metamorphic rocks4 ,thus it has a wide1 though by no means even1 distribution4 ,the soils formed by disintegration of these rocks probably all have some phosphorus in them2 but where there is vigorous plant growth1 it soon tends to become exhausted1 and must be renewed4 ,for this reason the use of phosphates has become of prime importance in ,agriculture4 ,the possession of beds of rock carrying phosphorus has come to be of international importance4 ,the ,united ,states is particularly fortunate in this respect1 and produces over #be of the world's supply of phosphates4 ,most all the phosphorus is recovered either from phosphate minerals1 the most important of which is apatite1 or from the non-crystalline and impure mixtures of phosphate minerals and other substances1 discussed under phosphate rock4 ,apatite ,ca,f7,,po7 ,pl4 #di ,occurs in crystals1 concretionary nodules1 or in bedded masses2 hardness1 #e2 specific gravity1 #c4b2 color reddish-brown or green1 rarely white or colorless2 luster vitreous2 translucent on thin edges4 ,apatite occurs in hexagonal prisms1 usually with the ends truncated by a basal plane1 and with one or more sets of pyramidal faces between the prism and the basal plane4 ,crystals range in size from tiny to over a foot in diameter4 ,there is but one cleavage and that is basal4 ,the crystal form1 cleavage1 and hardness will easily determine this mineral4 ,apatite is usually associated with igneous or highly metamorphic rocks1 such as granites1 gneisses1 and crystalline limestones4 ,while the phosphoric acid of apatite is highly desirable for use in fertilizers1 the crystals do not occur in sufficient abundance to make them commercially available1 and non-crystalline phosphate rocks are resorted to for this purpose4 ,crystals of apatite are found at ,norwich and ,bolton1 ,mass41 ,rossie and ,edenville1 ,n4 ,y41 ,suckasunny and ,hurdstown1 ,n4 ,j41 ,leiperville1 ,penn41 ,wilmington1 ,del41 etc4 ,templeton1 ,canada1 is perhaps the best known locality for fine apatite4 ,turquois ,h,al7,,oh7,cu7,,oh77,,po7 ,occurs in seams and incrustations2 hardness1 #f2 specific gravity1 #b4g2 color bluish-green2 streak blue2 luster waxy2 translucent to opaque on thin edges4 ,in this country this complex phosphate of aluminum and copper is found in streaks and patches in volcanic rocks1 but in ,persia comes from metamorphic rocks4 ,to the ,persians it was a magical stone1 protecting the wearer from injuries1 and among the ,pueblo ,indians it was regarded as of religious value in warding off evil4 ,the best turquois comes from ,persia1 but it has been found at several points in the ,united ,states1 as in ,los ,cerrillos and ,burro ,mts41 ,n4 ,m41 in ,mohave ,co41 ,ariz41 ,san ,bernardino ,co41 ,cal41 in ,nevada and ,colorado4 ,fluorine ,at ordinary temperatures the element fluorine is a colorless gas1 which was not obtained pure until #ahhh1 because it could not be contained in vessels of glass1 gold1 platinum1 etc4 ,at that time it was made and kept in a vessel composed of an alloy of platinum and iridium4 ,its most important compound is hydrofluoric acid1 a fuming liquid1 which is mostly used to etch or dissolve glass4 ,it occurs in several minerals1 like tourmaline1 turquois1 etc41 but the only one used to obtain the hydrofluoric acid is fluorite4 ,fluorite ,ca,f ,pl4 #ej ,fluor spar ,occurs in crystals and cleavable masses2 hardness1 #d2 specific gravity1 #c4b2 colorless or some shade of violet1 green1 yellow1 or rose2 luster vitreous2 transparent on thin edges4 ,fluorite usually occurs in beautiful cubic crystals1 often with the edges and corners beveled by smaller faces1 and occasionally in twins1 which seem to have grown through each other4 ,there is perfect cleavage parallel to each of the octahedral faces1 which often1 as in the illustration on ,plate #ej1 show as cracks cutting off the corners4 ,since fluorite loses weight and color on heating1 it is concluded that the colors are due to the presence of hydrocarbon compounds4 ,the red and the green fluorite when heated to above #bab ,f4 become phosphorescent1 as may be seen if they are thus heated and exposed to the light1 then taken into the dark4 ,fluorite is quite commonly the gangue mineral associated with metallic ores1 and is also likely to occur with topaz1 apatite1 etc4 ,it is generally in such places that it seems to have been deposited from hot vapors1 rising from igneous magmas4 ,it is the only mineral at all common from which fluorine can be obtained1 and is used for making hydrofluoric acid1 and other chemical compounds of this element4 ,it is1 however1 of much greater importance as a flux in reducing iron1 silver1 lead and copper ores4 ,in the industries it finds a place1 being used to make apochromatic lenses1 cheap jewelry1 and for the electrodes in flaming arc lamps4 ,fluorite is widely distributed1 some of the better known localities being ,trumbull and ,plymouth1 ,conn41 ,rossie and ,muscalonge ,lake1 ,n4 ,y41 ,gallatin ,co41 ,ill41 ,thunder ,bay1 ,lake ,superior1 ,missouri1 etc4 ,halite ,na,cl ,pl4 #ej ,salt ,occurs in crystals1 and in cleavable and granular masses2 hardness1 #b4e2 specific gravity1 #b4a2 colorless to white2 luster vitreous2 transparent on thin edges4 ,halite is common salt1 occurring in cubic crystals1 with perfect cubic cleavage4 ,its form1 hardness1 taste1 and solubility in water make it easy to determine4 ,halite is the most abundant salt in sea water1 making about #b4e out of the total of #c4e of solids in solution4 ,it is also a prominent1 when not the leading1 salt in solution in the waters of inland lakes1 like ,great ,salt ,lake1 or the ,dead ,sea1 there being #bj of halite in the former and #h in the latter1 though the total of solid in solution in the water of the ,dead ,sea is greater than that in ,great ,salt ,lake4 ,the great salt deposits are mostly the result of the evaporation of the water of arms or isolated portions of former oceans2 the salt1 gypsum1 etc41 left by the drying sea1 having been buried beneath later sediments4 ,other bodies of salt represent the disappearance of ancient lakes4 ,there are also the curious 8salt domes0 of ,louisiana and ,texas1 which are immense1 roughly circular1 subterranean masses of salt extending to as yet unknown depths which are thought to have been formed by masses of salt from some deep source bed pushing their way upward through the overlying formations by plastic flowage4 ,as the upthrust took place the sediments were arched into domes4 ,some of these domes are today important sources of rock salt4 ,there are extensive beds of salt under parts of ,new ,york1 ,michigan1 ,ohio1 ,oklahoma1 ,kansas1 etc41 which are mostly worked by drilling wells into the salt layer1 then introducing hot water to dissolve the salt4 ,the brine thus formed is pumped to the surface1 and the salt recovered by evaporation in pans4 ,during the process1 skeleton crystals of salt with concave faces may form1 but in ,nature the crystals are uniformly solid cubes4 ,boracite ,mg,cl,b,o ,occurs in small crystals or granular masses2 hardness of crystals1 #g2 of the masses1 #d4e2 specific gravity #c2 colorless to white2 luster vitreous2 transparent to translucent on thin edges4 ,small crystals1 associated with salt and gypsum1 occur in the beds and incrustations1 which result from the drying up of alkaline lakes1 especially in ,nevada and southern ,california4 ,the crystals are orthorhombic1 but appear like perfect cubes1 with the edges beveled and part of the corners cut4 ,they are not easily dissolved in water1 but quickly go into solution in hydrochloric acid4 ,colemanite ,ca,b,o #e;,h,o ,occurs in crystals or compact masses2 hardness1 #d4e2 specific gravity1 #b4d2 colorless to white2 luster vitreous2 translucent on thin edges4 ,the crystals when they occur1 are monoclinic2 but usually colemanite is a bedded deposit1 which has resulted from the drying up of a saline lake4 ,it was first found in ,death ,valley1 ,cal41 in #ahhb1 then near ,daggett1 ,cal41 and since then in several similar locations in ,nevada and ,oregon4 ,the deposits are of all grades of purity1 the colemanite being mixed with varying quantities of mud4 ,today this mineral is the chief source of borax1 which is used in medicines1 cosmetics1 colored glazes1 enamel1 and as a preservative4 ,borax ,na,b,o #aj;,h,o ,occurs in crystals or in powdery incrustations2 hardness1 #b2 specific gravity1 #a4g2 colorless to white2 luster vitreous2 translucent on thin edges4 ,the crystals are tiny and monoclinic1 this mineral being usually obtained by the evaporation of the saline waters of such lakes as ,clear and ,borax ,lakes in southern ,california1 or from the muds of salt marshes1 like ,searles ,borax ,marsh in ,california4 ,originally most of our borax came from a large saline lake in ,tibet1 but now most of it is obtained from colemanite4 ,borax is soluble in water1 giving it a sweetish taste4 ,sulphur ,s ,pl4 #ea ,occurs in crystals1 incrustations or compact masses2 hardness1 #b2 specific gravity1 #b2 color yellow2 streak yellow2 luster resinous2 translucent on thin edges4 ,aside from the numerous compounds1 such as the sulphides of the metals like pyrite1 galena1 sphalerite1 etc41 and the sulphates1 like gypsum1 barite1 anglesite1 etc41 sulphur occurs in its elemental form in ,nature4 ,in this case it may be in crystals1 which are orthorhombic and usually occur as octahedrons1 with the upper and lower ends truncated1 either by a basal plane1 or by a lower octahedron1 or by both4 ,incrustations and compact masses are1 however1 much the commoner mode of occurrence4 ,the incrustations are found mostly about volcanic regions1 where the sulphur has risen from the molten lavas as a sublimate1 and on cooling has been deposited in crevices or on the adjacent surfaces4 ,irregular masses of sulphur are often found where sulphide minerals1 like pyrite or galena have been decomposed in such a way as to leave the sulphur behind4 ,the extensive beds of sulphur are usually associated with gypsum1 and are thought to be the result of water1 containing bituminous matter1 so acting on gypsum as to remove the calcium and oxygen as lime1 and leave the sulphur4 ,finally many waters carry sulphates in solution1 from which the sulphur may be precipitated by certain sulphur bacteria1 making thus incrustations on the bottom of ponds or lakes4 ,sulphur is used for making matches1 gunpowder1 fireworks1 insecticides1 in medicine1 vulcanizing rubber1 etc4 ,it is widely distributed1 however1 most of the present world's production is from deposits associated with the 8salt domes0 of ,texas and ,louisiana4 ,a 8caprock0 of gypsum and anhydrite overlies many of these which often contains elemental sulphur4 ,wells are drilled into this1 and the sulphur is melted by the introduction of hot steam4 ,this melted sulphur is then pumped to the surface and run into molds4 ,some of the best known localities are ,sulphurdale1 ,utah1 ,cody and ,thermopolis1 ,wyo41 ,santa ,barbara ,co41 ,cal41 ,humboldt ,co41 ,nev41 and about the hot springs of the ,yellowstone ,park4 ,ice ,h,o ,pl4 #ea water ,occurs solid as ice1 snow and frost1 or liquid as water2 hardness1 #b2 specific gravity1 4#ib2 colorless to white2 luster adamantine2 transparent on thin edges4 ,though we seldom think of ice1 and its liquid form1 water1 as a mineral1 still it is one1 and perhaps the most important of all minerals1 as well as the most common4 ,ice melts at #cb ,f4 and vaporizes at #bab ,f41 being then termed steam4 ,because it is so common and liquid at ordinary temperatures it acts as a solvent for a host of other minerals1 and is therefore the agent by which they are transported from place to place and redeposited in veins and beds4 ,not only does water act as a transportation agent for minerals in solution1 but is also the agent of erosion and weathering4 ,water vaporizes slowly when exposed to the air at all temperatures above freezing1 and so it is slowly rising from the surface of the sea or lakes or moist ground into the air1 where it would accumulate until the air was saturated1 if the air would only keep still and at a uniform temperature4 ,the air will hold a given amount of water vapor1 which is1 for example1 #ag grams per cubic meter when the temperature is #fh ,f41 but at #ei ,f4 it will hold only #ab grams1 or at #ej ,f4 only #i grams4 ,thus the air is more or less completely saturated at higher temperatures1 and when the temperature is lowered the air can not hold all it has taken up1 and it is precipitated in dew1 rain or snow1 most often as rain4 ,when the rain falls it mechanically carries away1 and more or less slowly transports to other places particles of rock1 being thus the agent of erosion2 and when it is slowed down1 as on entering the quiet water of a lake or the sea1 it drops the mechanically carried sediment and makes sedimentary deposits4 ,another very important and unique feature of water is that on freezing it expands about _/th of its former bulk1 so that1 as a result1 ice floats1 and also wherever water in crevices is frozen1 the crevices are enlarged4 ,in locations where this freezing and melting take place repeatedly throughout a year1 there the breaking up of rocks is rapid4 ,this is hardly the place to take up a complete discussion of water1 but its action as a solvent1 mechanically1 and in freezing1 melting1 and vaporizing is the basis of a large part of the study of geology4 ,when water crystallizes1 as in forming ice1 it is in the hexagonal system4 ,it tends to twinning and a snow-flake is made up of a large number of twinned crystals1 each diverging from the other at #fj4 ,when ice is formed in the air or on the surface of water it forms these complex and beautiful multiple twins1 of which but a couple are suggested here4 ,beneath the surface the hexagonal crystals grow downward into the water1 parallel to each other1 making a fibrous structure1 which is very apparent when ice is 8rotten10 which is the time at which the surfaces of the prisms are separating1 because the molecules leave the crystal in the reverse order to which they united with it4 ,frost in marshy or spongy ground will often show this fibrous growth beautifully4 ,,chapter ,,iv ,,the ,,rocks ,broadly speaking a rock is an essential part of the crust of the earth1 and includes loose material1 like sand1 mud1 or volcanic ashes1 as well as compact and solid masses1 like sandstone and granite4 ,rocks are aggregates of minerals1 either several minerals grouped together1 as are mica1 quartz and feldspar to make granite1 or large quantities of a single mineral1 like quartz grains to make sandstone4 ,the rocks are most conveniently classified according to their mode of origin1 into three main groups1 igneous1 sedimentary1 and metamorphic4 ,the igneous rocks are those which have solidified from a molten magma1 like lavas1 granites1 etc4 ,the sedimentary rocks are those which represent accumulations of fragments or grains1 derived from various sources1 usually the weathering of other rocks1 and deposited by such agents as water1 wind and organisms4 ,metamorphic rocks are those which were originally either igneous or sedimentary1 but have been altered by the actions of heat1 pressure and water1 so that the primary character has been changed1 often to such an extent as to be obscured4 ,rocks once formed in any of the above ways are being constantly altered in character by the various processes of nature4 ,those exposed on the surface are weathered to pieces1 and the fragments are transported by wind or water to accumulate elsewhere as sedimentary rocks4 ,those buried deep beneath the surface are affected by the high temperature and pressure of the depths of the earth and thus metamorphosed4 ,for instance a granite exposed on the surface is slowly weathered1 some parts being carried away in solution by the rain water1 others less soluble remaining as grains of quartz1 mica or kaolin4 ,these are transported by water and sorted1 the finer kaolin being carried to still and deep water1 the quartz and mica accumulating in some lowland as sand4 ,this sand will in time be cemented to a sandstone1 later slowly buried beneath the surface4 ,if buried deep it will feel the effect of the interior temperature1 which increases as one goes down at the rate of one degree ,f4 for every #ej feet4 ,if this should be in a region where folding and mountain-making takes place1 the material under the folds would be melted 7because of the relief from pressure which would permit the high temperature to act freely7 and become igneous rock1 either coming to the surface as lava1 or remaining below the surface and making a granite or similar rock2 while the sedimentary material not melted but near enough to the molten material to be affected1 would be metamorphosed1 in this case to a quartzite4 ,much of the interest and profit in studying rocks1 will come from the understanding which they will give as to the history of that particular part of the earth's crust where they are found4 ,igneous ,rocks ,igneous rocks are those which have formed from material that has been melted1 which involves temperatures around #acjj ,c42 or1 if there is water in the original material1 temperatures as low as #hjj ,c4 will suffice4 ,considering the increase of temperature to be a degree for every #ej feet downward1 this involves the rocks having been at depths of #e to #aj miles below the surface4 ,while at such depths the temperature must be high enough to melt rocks1 the great pressure of the overlying rocks seems to keep them solid2 for we know that the center of the earth is solid1 as is shown by a variety of observations1 such as the rate at which earthquake waves are transmitted through the earth1 the lack of tidal effects1 etc4 ,however1 there is every reason to believe that if the pressure is removed from the rocks which are five to ten miles below the surface1 there is heat enough at those depths to melt them4 ,when the crust of the earth is folded1 as when mountain ranges are formed1 the areas under the arches or upward folds are relieved of pressure4 ,then those rocks1 which are under the arches and are relieved1 become molten4 ,the molten magma may well up and fill the space beneath the arch where it would cool again very slowly2 or1 if there is fissuring during the folding1 some of the molten material may be forced out through the fissures and pour out over the surface as lava4 ,another area in which pressures may be locally relieved is in the region of faulting1 where the crust of the earth is broken into blocks1 between which there are readjustments1 some being tipped one way1 some another1 some uplifted4 ,here again there would be areas of relieved pressure and molten magmas would form1 some of them solidifying in place1 others rising to the surface4 ,the molten material is termed the magma1 and when it reaches the surface1 great quantities of water vapor and other gases escape3 or these gases may even escape from magmas which do not reach the surface1 rising through fissures4 ,as these hot vapors pass through the fissures1 they are cooled1 and may deposit part or all of their dissolved compounds in the fissure1 making veins4 ,lava is the magma minus the vapors4 ,magmas vary greatly from place to place1 indicating that they are formed locally and do not come from any general interior reservoir1 as has sometimes been suggested4 ,when the molten magmas escape to the surface1 they are termed extrusive1 and as they spread out in a layer this is termed a sheet4 ,this rise and overflow may be quiet1 and from time to time one outpouring may follow another making sheet after sheet4 ,or after one outpouring1 the pressure below may cease for a time and allow the lava to solidify and make a cap or cover over the opening4 ,before more lava can rise1 this cover must be removed4 ,this usually happens in an explosive manner1 the lava below1 with the increasing pressure exerted by its expanding gases1 finally exerting enough pressure1 so that the cover is broken1 or shattered and thrown in thousands of fragments into the air1 as happened at ,mt4 ,pele on the ,island of ,martinique in #aijb4 ,the fragments thrown into the air are often termed volcanic ashes1 though this is not a good word for them1 for they have not been burned4 ,in case the molten magmas under the relieved areas do not reach the surface they are termed intrusive4 ,such magmas may remain in the space under a mountain fold1 or be forced in fissures part way to the surface4 ,when the magma is forced into more or less vertical cracks and there solidifies1 and these are exposed by erosion1 they are termed dikes4 ,sometimes the magmas have risen part way to the surface and then pushed their way between two horizontal layers of rock and there hardened1 in which case they are termed sills1 when uncovered4 ,the ,palisades along the ,hudson ,river are the exposed edge of a sill4 ,again the molten magmas may well up and spread between two horizontal layers1 but come faster than they can spread horizontally1 and then the magma takes the form of a half sphere1 and the overlying layers of rock are domed up over it4 ,such a mass is termed a laccolith4 ,in all these cases the mass of igneous rock is only discovered when the overlying rocks have been eroded off4 ,the great mass of molten magma under the arches of mountain ranges simply cools slowly into a granitic type of rock4 ,these masses are exposed when the thousands of feet of overlying rock are eroded off4 ,when these masses are exposed1 if of but a few miles in extent1 they are called stocks1 but1 if of many miles in length and breadth1 they are batholiths1 and are very characteristic of the heart of mountain ranges4 ,in all the above cases the exterior of the molten mass cools first1 and forms a shell around the rest4 ,the shell determines the size of the mass4 ,as the cooling continues into the interior1 it also solidifies1 and as all rocks shrink on cooling1 cracks develop1 separating the mass into smaller pieces4 ,there is usually no regularity about these cracks and the mass is divided into blocks from six inches to three feet in diameter4 ,however1 in some cases1 especially in sills and laccoliths where the cooling is slower1 the shrinkage may be marked by a regular system of cracks which bound the rock into more or less regular hexagonal columns4 ,the ,palisades and the ,devil's ,tower in ,wyoming 7,see ,plate #eb7 show this structure4 ,the ,devil's ,tower is the remnant of a laccolith1 all except the central core of which has been eroded away4 ,all of the above terms have nothing to do with composition1 but refer entirely to the manner of occurrence4 ,while the igneous rocks are classified according to their composition1 the rate at which they cooled has much to do with their texture1 and certain names apply to the texture4 ,for instance when the molten lava cools very rapidly1 there is no time for the formation of crystals1 and the resulting rock is glassy or non-crystalline4 ,if the cooling is slow as in large bodies1 crystals have time to form and grow to considerable size as in granites4 ,between these all grades may occur2 and one classification of igneous rocks expresses their rate of cooling1 in such terms as the following4 ,glassy--lavas which have cooled so quickly that they are without distinct crystallization1 such as obsidian1 pitchstone1 etc4 ,dense or felsitic--lavas which have cooled less rapidly1 so that crystals have formed1 but in which the crystals are too small to be identified by the unaided eye1 such as felsite or basalt4 ,porphyritic--magmas from which1 in solidifying1 one mineral has crystallized out first and the crystals have grown to considerable size1 while the rest have remained small4 ,granitoid--magmas which have solidified slowly1 so that all the minerals have crystallized completely1 and the component crystals are large enough to be recognized readily1 as in granite4 ,fragmental--a term applied to the fragments which have resulted from explosive eruptions of igneous rocks4 ,these fragments may be loose or consolidated4 ,volcanic ashes are typical4 ,porous--a term applied to the lava near the upper surface1 which is filled with gas cavities1 such as pumice4 ,amygdoloidal--is the term applied to porous lavas1 when the cavities have been filled by other minerals1 such as calcite or some of the zeolites4 ,in determining a rock1 first decide whether it is igneous1 sedimentary or metamorphic4 ,the igneous character is recognized by its being either glassy1 or composed of masses of crystals irregularly arranged1 there being neither layering nor bedding4 ,,classification ,,of ,,igneous ,,rocks ,texture ,excess of light colored minerals ,excess of dark colored minerals ,glassy obsidian1 perlite1 pumice1 pitchstone scorias1 trachylyte1 basalt-obsidian ,feldspar orthoclase ,feldspar ,plagioclase ,no feldspar ,mica and_/or hornblende and_/or augite ,mica and_/or hornblende with pyroxene augite and_/or hornblende and_/or mica quartz -quartz quartz -quartz olivine -olivine olivine -olivine ,dense rhyolite trachite dacite 7felsite7 andesite 7felsite7 basalt augitite or hornblendite ,porphyritic rhyolite-porphyry trachite-porphyry dacite-porphyry andesite-porphyry basalt-porphyry augitite-porphyry ,granitoid granite syenite quartz-diorite diorite olivine-gabbro gabbro peridotite pyroxenite ,fragmental rhyolite1 tuff trachite1 tuff ,dacite1 tuff or andesite tuff or ,basalt tuffs and breccias or breccia or breccia breccia breccia ,when it is located as igneous1 turn to the key on page #agg and decide as to which type of texture is present4 ,if glassy1 the color1 luster and type of construction will place it4 ,if the rock is crystalline1 first decide whether feldspar is present1 and if present1 what type3 then determine the dark mineral1 and lastly whether quartz or olivine is present4 ,in dense rocks the presence of quartz may be determined by trying the hardness1 for none of the other constituents of igneous rocks have so great hardness4 ,for example1 if it is found that a rock is composed of orthoclase hornblende and quartz1 and the texture is granitoid1 it is granite3 or if the rock is plagioclase feldspar and pyroxene of any sort1 it is gabbro1 etc4 ,granite ,pl4 #ec ,the combination of orthoclase feldspar 7or microcline71 quartz1 and either mica1 hornblende or augite is termed granite1 if the texture is coarse enough so the individual minerals can be recognized with the unaided eye4 ,the rock is light-colored because the feldspar and quartz dominate4 ,accessory minerals may be present such as apatite1 zircon1 beryl or magnetite4 ,varieties of granite are distinguished according to the dark mineral present4 ,when this is muscovite1 it is a muscovite-granite2 when it is biotite1 a biotite-granite2 if it is hornblende1 a hornblende-granite2 etc4 ,the size of crystals in granite varies widely4 ,when they are as small as _/ of an inch in diameter1 it is termed fine grained2 from _/ to of an inch1 it is medium-grained2 when larger1 it is coarse-grained4 ,in some cases the crystals may be over a foot in diameter which is known as giant granite4 ,originally granite was a great mass of molten magma1 which has cooled very slowly1 having been intruded or thrust up in great stocks or batholiths beneath overlying rocks1 which acted as a blanket to prevent rapid cooling4 ,these overlying rocks1 in their turn1 have been acted upon by the heat and metamorphosed4 ,granite is particularly likely to have been formed under mountain folds2 so that1 after the mountains have been more or less completely eroded away1 the great masses of granite have come to the surface to mark the axes of the ranges2 and even after the mountains have been wholly worn away1 the granite remains to mark the sites on which they stood4 ,in the granite mass itself1 there are often veins and dikes1 which probably resulted from the shrinkage of the cooling granite1 and they are filled with a different and usually coarser granite known as pegmatite4 ,this pegmatite formed from the residual magmatic material1 so that as some of the elements had already crystallized out1 the granite in these dikes is of different composition4 ,the extreme coarseness of these pegmatites seems to be due to the character of the mineralizing agents left in the dikes4 ,in some of these pegmatites the feldspar and quartz are so intergrown1 that when broken along the cleavage surface of the feldspar1 the quartz appears like cuneiform characters1 and this variety has been given the name graphic granite 7,see ,plate #ec74 ,when granite is exposed to weathering1 the feldspar is the first mineral to be decomposed1 altering eventually into carbonates1 quartz and kaolin4 ,the dark minerals are only slightly less susceptible and they break down into carbonates1 iron oxides and kaolin4 ,the original quartz remains unchanged4 ,of these products the carbonates1 some of the iron oxide and a little of the quartz are carried away in solution4 ,the kaolin and some of the iron oxide is in fine particles and they are carried by the water until it comes to the lakes or the sea4 ,the quartz is left in coarser grains1 which are more slowly transported1 and deposited in coarser or finer sand and gravel beds4 ,granites are widely used for building stone1 because they can be worked readily in all directions1 and have great strength and beauty4 ,the color depends largely on the color of the feldspar1 which may be white or pink1 in which case the granite will be gray to pink4 ,granites occur throughout ,new ,england1 the ,piedmont ,plateau1 the ,lake ,superior ,region1 the ,black ,hills1 ,rocky ,mountains1 ,sierra ,nevada1 etc4 ,syenite ,pl4 #ed ,the combination of orthoclase and either mica1 hornblende1 or augite is syenite1 the texture being coarse enough so that the individual minerals can be distinguished by the unaided eye4 ,it differs from granite in the absence of quartz4 ,syenite is a light-colored rock with the feldspar predominating4 ,minerals like apatite1 zircon1 or magnetite may occur in it1 as accessory minerals4 ,the foregoing would be an ideal syenite1 but usually there is some plagioclase feldspar also present4 ,if this occurs in such quantities as to nearly equal the orthoclase feldspar1 the rock is termed a monzonite2 if it predominates1 the rock becomes a diorite4 ,the presence of quartz would make this rock into a granite4 ,such a compound rock has its type form1 and when the proportions of the component minerals are changed1 it grades into other types4 ,like the granite1 syenite is an intrusive rock1 which occurs in stocks and batholiths along the axes of present or past mountain ranges4 ,the original magma welled up under the mountain folds1 where it cooled slowly1 metamorphosing the adjacent rocks4 ,like granite it has only been exposed after a long period of erosion has removed the overlying layers of rock4 ,syenites are not as abundant as granites1 but they occur in the ,white ,mountains1 near ,little ,rock1 ,ark41 in ,custer ,co41 ,colo41 etc4 ,quartz-,diorite ,the combination of plagioclase feldspar1 quartz and either mica or hornblende makes quartz-diorite1 sometimes called tonalite4 ,the above would be the typical quartz-diorite1 but there is usually some orthoclase present1 which if it equals the plagioclase feldspar in amount makes this into a monzonite2 or if it dominates1 it makes the rock a granite4 ,quartz-diorite is darker colored than the two preceding rocks1 the dark minerals being about as abundant as the light-colored ones1 such as feldspar and quartz4 ,for this reason the weight is also somewhat greater4 ,like the others this is an intrusive rock1 occurring in stocks and batholiths1 and indicative of great molten masses thrust up under mountain folds1 and only exposed after the overlying rocks have been weathered away4 ,it is by no means an abundant type of rock1 but occurs at ,belchertown1 ,mass41 ,peekskill1 ,n4 ,y41 in the ,yellowstone ,park1 etc4 ,diorite ,plagioclase feldspar with hornblende or mica1 or with both1 is known as diorite4 ,it is distinguished from quartz-diorite by the absence of quartz4 ,there is generally some augite in it1 but if this should be equal to1 or exceed the hornblende1 the rock is then a gabbro4 ,there may also be a small amount of orthoclase present1 without taking this rock out of the diorite class1 but if the orthoclase feldspar becomes dominant1 then the rock is a syenite4 ,thus there is gradation into other groups in all directions4 ,apatite1 magnetite1 zircon1 and titanite often occur in small quantities as accessory minerals4 ,generally the hornblende is in excess of the feldspar1 so that the rock is a dark-colored one4 ,diorites occur in much the same manner as granites1 being in stocks1 batholiths or dikes1 and are often associated with granites and gabbros4 ,they are great intruded masses1 associated with mountain making1 and like the preceding rocks1 cooled far below the surface1 and have been exposed only after great thicknesses of overlying rocks have been weathered away4 ,peekskill1 ,n4 ,y41 the ,sudbury nickel district in ,canada1 ,mt4 ,davidson above the ,comstock ,lode in ,nevada1 etc41 are typical localities for finding diorite4 ,olivine-,gabbro ,the combination of plagioclase feldspar with augite 7or any of the pyroxenes7 and olivine makes olivine-gabbro4 ,the feldspar is usually one of those with considerable calcium in it1 like labradorite2 and as the dark minerals predominate1 the rock is dark-colored4 ,it is an intrusive rock1 usually in dikes or stocks1 where it solidified far below the surface1 and was only exposed after the overlying rocks were weathered off4 ,it is by no means an abundant type of rock1 but is found in the ,lake ,superior ,region1 and near ,birch ,lake1 ,minn4 ,gabbro ,pl4 #ed ,plagioclase feldspar with any one of the pyroxenes1 most commonly augite1 is gabbro4 ,there is a wide range in the relative proportions of the two minerals making gabbro4 ,at one extreme are rocks made entirely1 or almost entirely1 of plagioclase feldspar1 which are known as anorthosites1 and occur in parts of the higher mountains of the ,adirondacks like ,mt4 ,marcy1 in several places in eastern ,canada1 etc4 ,then there are the typical gabbros where the feldspar and augite are more or less equally represented4 ,at the other extreme come those gabbros in which the pyroxene predominates1 in the most marked cases the feldspar being entirely lacking1 and the rock being termed a pyroxenite4 ,when the pyroxene of a gabbro is either enstatite or hyposthene 7usually the latter7 the gabbro is often called norite4 ,magnetite1 biotite1 and hornblende may occur in small quantities as accessory minerals4 ,gabbro is a common intrusive rock1 occurring in stocks1 batholiths1 and dikes1 and often varies considerably in different parts of the mass4 ,like granite the mass solidified far below the surface1 under some mountain fold1 and has only been exposed as the result of weathering away the layers of overlying rock4 ,gabbros appear much like diorites1 but are distinguished by the fact that the dark mineral is one of the pyroxenes1 instead of an amphibole or a mica4 ,they are widely distributed1 being found in the ,white ,mountains1 near ,peekskill1 ,n4 ,y41 ,baltimore1 ,md41 about ,lake ,superior1 in ,wyoming1 the ,rocky ,mts41 etc4 ,peridotite ,a rock made up of olivine and augite 7or any of the pyroxenes7 is peridotite4 ,as it contains no feldspar1 and both augite and olivine are dark-green to black in color1 these rocks are always dark green to black in color and of considerable weight4 ,they are usually rather coarsely crystalline4 ,peridotite is usually associated with gabbro1 making dikes which lead from the main gabbro mass4 ,less frequently it occurs independently1 making up an intrusive mass4 ,hornblende and mica may be present in small quantities1 as accessory minerals4 ,in general these are rather rare rocks1 making dikes connected with stocks or batholiths of gabbro4 ,peridotite is found near ,baltimore1 ,md41 in ,custer ,co41 ,colo41 in ,kentucky1 etc4 ,pyroxenite ,this represents the extreme among coarsely crystalline igneous rocks1 a whole mass made up of one mineral1 and that some one of the pyroxene group4 ,if the mineral can be exactly determined1 the rock may be still more definitely named4 ,for instance if it is all augite1 then the rock would be called augitite4 ,like the preceding rocks1 pyroxenite is an intrusive rock1 usually found in dikes1 which are connected with gabbro1 and it represents the segregation of one mineral out of the gabbro1 and its solidification at one point4 ,hornblende1 magnetite and pyrrhotite may be present as accessory minerals4 ,this is not a common rock1 but it illustrates the fact that all possible combinations do occur1 if the circumstances have warranted it4 ,it is found near ,baltimore1 ,md41 ,webster1 ,n4 ,c41 and in ,montana4 ,rhyolite ,this is a combination of orthoclase feldspar1 quartz1 and either hornblende1 mica or augite in which the crystals are of such small size that they can not be identified with the naked eye4 ,in composition it corresponds to granite1 but it is much finer in texture4 ,it differs from trachite by having quartz while the latter has none4 ,this can usually be determined by trying the hardness as none of the other minerals are as hard as #g4 ,it is much harder to distinguish it from dacite which differs only in having plagioclase feldspar in place of the orthoclase1 and only the microscope will enable one to make this distinction4 ,where the distinction cannot be made these light-colored lavas are often called felsite4 ,rhyolite is usually an extrusive lava1 occurring in sheets1 but sometimes it is intrusive1 occurring in sills1 dikes1 and laccoliths4 ,in all these cases the lava has solidified so rapidly1 that the crystals are tiny1 and only the general effect of a crystalline structure is distinguishable4 ,rhyolites may occur with porphyritic structure1 in which case the presence of the larger feldspar crystals will help to distinguish whether they are orthoclase or not1 making the determination easier4 ,the color of rhyolites is green1 red or gray1 always a decided light shade4 ,rhyolites are abundant in the western states1 as in the ,black ,hills1 the ,yellowstone ,park1 ,colorado1 ,nevada1 ,california1 etc4 ,trachite ,the combination of orthoclase feldspar with mica1 hornblende or augite is termed trachite1 if the texture is dense4 ,it is usually an extrusive lava of light color 7green1 red or gray71 and corresponds in composition to syenite4 ,it can be distinguished from rhyolite by having no quartz1 and so nothing to show a hardness above #e4e2 but it is difficult to distinguish it from andesite1 which differs only in having plagioclase feldspar in place of orthoclase4 ,it sometimes occurs with a porphyritic structure1 in which case the feldspar crystals are usually large enough to be distinguished4 ,trachites are not abundant in ,america1 but some are found in the ,black ,hills of ,south ,dakota1 in ,custer ,co41 ,colo41 and in ,montana4 ,dacite ,the union of plagioclase feldspar1 quartz1 and either hornblende or mica is termed dacite1 if the texture is dense4 ,it is an extrusive lava1 occurring mostly in sheets and dikes4 ,it corresponds in composition to quartz-diorite4 ,as the texture is dense it is difficult to distinguish dacite from rhyolite1 for both have quartz and differ only in the character of the feldspar1 so it is quite common to use the term felsite which does not distinguish between the two1 and only states that the rock is dense1 light-colored and extrusive4 ,when1 as often occurs1 the texture is porphyritic1 and the feldspars are the large crystals1 then exact determination is fairly easy4 ,dacites are rather common1 occurring on ,mc,clelland ,peak1 ,nev41 in the ,eureka district1 ,nev41 on ,lassen's ,peak1 ,calif41 ,sepulchre ,mt4 in the ,yellowstone ,park1 etc4 ,andesite ,the union of plagioclase feldspar with mica1 hornblende or augite1 makes andesite if the texture is dense4 ,the lack of quartz1 and so no mineral which has a hardness of over #e4e1 makes it possible to distinguish andesite from dacite or rhyolite1 but it is hard to distinguish this rock from trachite1 which differs only on having orthoclase feldspar in place of plagioclase4 ,when the texture is porphyritic and the feldspars are the large crystals1 then it is easy to make the distinction4 ,andesite gets its name from being the characteristic lava of the ,andes ,mountains1 and is the commonest of all the extruded1 light-colored lavas1 being the lava of hundreds of flows throughout the western ,united ,states4 ,the union of plagioclase feldspar and biotite is the commonest type4 ,plagioclase with hornblende or augite is less common1 and1 when they do occur1 they are usually distinguished as hornblende-andesite or augite-andesite4 ,magnetite1 apatite and zircon may be present as accessory minerals4 ,the lavas of ,mt4 ,hood1 ,shasta1 ,rainier and others of the volcanic peaks of the ,cascade ,range1 those at ,eureka and ,comstock in ,nevada1 in the ,yellowstone ,national ,park1 and the porphyries of many peaks in ,colorado1 like the ,henry ,mts41 etc41 which are exposed laccolithic intrusions1 are all andesites1 as are many more4 ,basalt ,the combination of plagioclase feldspar with olivine and augite 7or any other pyroxene7 makes a heavy1 dark-colored1 black to dark-brown rock which1 if its texture is dense or porphyritic1 is termed basalt4 ,this usually has more or less magnetite in it as an accessory mineral1 indeed the magnetite may be so abundant as to be a component part of the rock4 ,this magnetite makes trouble for anyone trying to use a compass on or about basalt rocks4 ,these are extrusive or intrusive rocks and correspond in composition to gabbro4 ,basalts are among the commonest of igneous rocks1 and are popularly designated 8trap10 much used as a road ballast on account of its toughness1 which is largely due to its dense texture4 ,the coast of ,new ,england is seamed with dikes of basalt1 and through the ,adirondack and ,white ,mountains there are a host of these dikes4 ,the crests of such mountains1 as the ,holyoke ,range1 the ,tom ,range1 the ,talcott ,mts41 ,east and ,west ,rocks at ,new ,haven1 etc41 are all basalt sheets4 ,the ,palisades1 ,first ,wachung and ,second ,wachung ,mountains of ,new ,jersey are sills of basalt4 ,the ,lake ,superior region is crisscrossed with basalt dikes4 ,that greatest of all lava fields the ,columbia ,plateau1 covering over #bjj1jjj square miles on the ,snake and ,columbia ,rivers in ,oregon1 ,washington and ,idaho1 is all basalt4 ,so it goes all down through ,nevada1 ,new ,mexico and ,california4 ,porphyry ,pl4 #ee ,this is a term which properly refers to texture alone1 indicating a lava1 which has cooled in such a manner that one mineral has crystallized out of the magma first and developed to a larger size1 while the mass of the material formed tiny crystals in which the larger ones are embedded4 ,the large crystals are technically known as phenocrysts4 ,the surrounding mass of tiny crystals is termed the matrix4 ,this porphyritic structure is especially characteristic of lavas which have been extruded in large masses1 and of intruded lavas in such places as sills and laccoliths4 ,the term porphyry today has the above precise meaning4 ,it is a much abused word1 and has had all sorts of meanings4 ,in the past it was first used to refer to lavas in general1 then it came to be applied to lavas which had been erupted before ,tertiary times1 that is to all ancient lava sheets4 ,this idea soon proved incorrect1 lavas being of the same composition whether ancient or recent4 ,in the ,west the word is often colloquially used today to designate almost every kind of igneous rock occurring in sheets or dikes1 if in any way connected with ore deposits4 ,when the composition of a rock with porphyritic textures can be determined1 the name due to the composition is coupled with that due to texture1 making such terms as trachite-porphyry1 basalt-porphyry1 etc4 ,tuff ,tuff1 a term not to be confused with tufa on page #bae1 is the name used to designate the finer fragmental ejecta of volcanic eruptions1 which are also often referred to as 8volcanic ash10 but the word1 ash1 conveys the false impression that the rock is a remnant of something burned1 and is therefore not a good term4 ,when first ejected1 tuff is loose material1 but it is usually soon cemented to make a more or less firm mass of rock1 for which the term1 tuff1 is still retained4 ,in some cases1 while still loose1 it is carried by streams to a distance and deposited in more or less sorted and layered beds3 and the finer tuff is often carried by the winds and laid down1 at a considerable distance from its source1 in so called 8ash beds40 ,in both these cases1 sedimentary characteristics have been added to the tuff1 and layering which is characteristic of sedimentary deposits1 is present4 ,these transported tuff beds are really sedimentary1 but as there is little change in the material1 they are referred to here and not again4 ,these tuff beds are not at all uncommon in the sedimentary deposits of ,tertiary age in the ,rocky ,mountain region4 ,the coarser material of volcanic eruptions usually goes under the head of breccia4 ,breccia ,this term is used to describe the coarse fragmental ejecta of volcanic eruptions4 ,it is also used1 in the section under sedimentary rocks1 in a broad sense to include all angular unworn fragmental material1 whether of igneous or sedimentary origin4 ,for this reason1 when dealing with igneous rocks1 it is usual to designate the fragments according to their composition1 making such terms as trachite-breccia1 rhyolite-breccia1 etc4 ,while still loose 7and also even when cemented into beds of rock71 it is customary to designate the smaller fragments1 from the size of a grain of wheat up to an inch or two in diameter1 as lapilli2 the larger fragments1 from two inches up to a foot or so in diameter1 as bombs2 and the largest masses1 often tons in weight1 as volcanic blocks4 ,obsidian ,pl4 #ee ,lavas1 which have cooled so quickly that crystals have not had time to form1 have a glassy appearance1 and are termed obsidian4 ,if the color is dark1 due to the presence of large amounts of those elements which make dark minerals1 this lava is termed basalt-obsidian4 ,obsidian is characterized by its glassy texture1 a hardness around #f1 and by breaking with a conchoidal fracture1 so called because the surface is marked by a series of concentric ridges1 something like the lines of growth on a shell4 ,obsidians vary greatly in color1 but are usually red or green to black1 and translucent on thin edges4 ,while glassy1 all the obsidians contain embryonic crystals1 which appear like dust particles floating in the glassy matrix1 or there may even be a few larger crystals present1 which are often arranged in flow lines4 ,most all large masses of obsidian have streaks or layers of stony material in them where crystallization has set in1 in a limited way4 ,near the upper surface1 obsidians usually have gas cavities scattered through them1 and these may be small and few1 or large and numerous4 ,indeed the cavities may be so numerous as to dominate and give the rock a frothy appearance4 ,in this case1 if the cavities are small and more or less uniform1 the rock is called pumice2 if they are larger it is scoria4 ,if1 as often happens when the lava is ancient and has been buried beneath other rocks1 the cavities have been filled with some secondary mineral1 then the lava is called an amygdoloid4 ,obsidian is found in many localities1 especially where there are recent volcanoes1 the most famous places being the obsidian cliffs in the ,yellowstone ,park1 those near ,mono ,lake in ,california1 and many other localities in the ,rocky ,mountains1 the ,sierra ,nevadas1 and the ,cascade ,mountains4 ,pitchstone ,this is very like obsidian in appearance1 but differs in that the glassy material contains from five to ten per cent of water in its composition1 the most obvious effect of which is to make the luster resinous1 instead of vitreous1 as is characteristic of obsidian4 ,the colors are commonly red1 green or brown4 ,pitchstone is associated with recent volcanoes1 and some fine specimens have come from ,silver ,cliffs1 ,colo41 and various parts of ,new ,mexico and ,nevada4 ,perlite pearlstone ,perlite is a glassy lava1 containing two to four per cent of water1 which1 on cooling1 has cracked into numerous rounded masses1 with a concentric structure1 reminding one of the layers of an onion4 ,scoria ,while lava is cooling1 there is a constant escape of gases1 mostly steam1 and as these rise through the molten mass they make cavities1 near the upper surface1 that portion on top often becoming frothy4 ,if this solidifies quickly so that the gas cavities are preserved it is scoria4 ,when the gas cavities are small and uniformly distributed1 the rock is called pumice1 and often used as a scouring agent4 ,when the cavities are large and irregular the term scoria is generally used4 ,molten lavas may form various structures1 according to the conditions under which they cool1 dripping through cracks or from the roof of caves1 which often form where the molten lava escapes from a hardened shell1 and making stalactites1 stalagmites1 etc4 ,the very thin lava of the ,hawaiian volcanoes may even be blown by the wind into fine threads1 known as 8,pele's hair40 ,the presence of the gas cavities is so characteristic of the upper surface of lavas which have been extruded2 that1 where one is dealing with older lavas1 now buried beneath other rocks1 this fact helps to determine whether the mass is a sheet1 rather than a sill2 for1 in the case of the sill1 the lava was forced between layers of sedimentary rocks1 and the burden of the overlying rocks did not permit the escape of steam and therefore the upper surface of sills does not have the scoriaceous structure4 ,amygdoloid ,pl4 #ef ,when the upper surface of a lava is filled with steam holes1 and this lava has been buried beneath other rocks1 the seeping waters slowly bring such minerals as quartz1 calcite and zeolites and fill the cavities4 ,such a rock is known as an amygdoloid4 ,it is often confused with porphyry2 but1 if examined closely1 it will be seen that the outlines of the gas cavities are rounded1 while the outlines of a crystal1 like a phenocryst1 are always angular4 ,this will be clear if the amygdoloid on ,plate #ef is compared with the porphyry on ,plate #ee4 ,the ,sedimentary ,rocks ,to this class belong all those rocks which have been laid down by water or wind1 or are the results of organic depositions4 ,they include loose material like sand or day1 and also the same materials1 when cemented into more or less solid rocks1 like sandstone or shale4 ,so long as the material has not been altered from what it was when laid down1 the rock is termed sedimentary4 ,in general the material of which these rocks are composed comes from the weathering and disintegration of other rocks4 ,this does not apply to the organic deposits1 for each type of which there is a peculiar mode of formation4 ,to illustrate the typical formation of sedimentary rocks1 we may look at the fate of a granite when exposed4 ,at once the surface is attacked by changes of temperature1 frost and rain4 ,the various minerals of the granite expand and contract with every change of temperature1 but each component mineral has a different coefficient of expansion under heat1 so that minute cracks are quickly formed between the minerals4 ,water gets into these cracks and begins to dissolve the minerals4 ,feldspar is the most easily attacked1 part of it being dissolved and carried away1 a small part changing to quartz1 and by far the largest part changing to kaolin4 ,the dark mineral is also attacked and partly dissolved1 and partly changed to kaolin and iron oxides4 ,the quartz resists solution almost completely4 ,of these products the kaolin and iron oxides are carried far away and deposited in still water4 ,the quartz and perhaps some of the dark mineral are heavier and carried more slowly1 being deposited as sand4 ,this happens to granite everywhere1 but in the regions where there is frost the action is greatly hastened2 for water gets into the cracks and expands every time it freezes and thus widens the cracks rapidly1 which greatly facilitates the entrance and movement of water in the rock4 ,in a similar way any original rock will be disintegrated1 and the residue1 after the soluble part has been carried away1 becomes sand or clay or mud4 ,particles of quartz1 kaolin1 and lime1 separately1 or mixed1 loose or more or less cemented1 with accompanying impurities1 make up the great bulk of the sedimentary rocks4 ,they are usually arranged in layers1 of varying thickness1 as they were laid down by water or the wind4 ,in the same way layered accumulations which are either products of plants or animals1 or parts of the plants or animals1 are considered sedimentary1 as for instance1 coal1 chalk1 petroleum1 etc4 ,a ,classification of ,sedimentary ,rocks ,inorganic origin3 #a4 ,coarse fragmentary material talus resulting from weathering #b4 ,the same fragmentary material breccia cemented #c4 ,unsorted material resulting from soil rock weathering #d4 ,coarse fragments rounded by the gravel action of water and wind #e4 ,the same material cemented conglomerate #f4 ,finer material deposited by water sand or wind #g4 ,the same material cemented sandstone #h4 ,the finest material1 mostly clay kaolin1 deposited by water #i4 ,the finest material1 deposited by loess wind #aj4 ,the same material cemented shale #aa4 ,fine particles of lime1 pure or marl impure #ab4 ,the same material cemented limestone #ac4 ,unassorted material left by the till glacial ice #ad4 ,the same material cemented tillite ,organic ,origin3 #ae4 ,limes made from shells1 etc4 coquina1 chalk1 coral rock1 etc4 #af4 ,silica from the shells of plants1 diatomaceous earth1 etc4 etc4 #ag4 ,carbon from plants peat1 lignite1 coal1 etc4 #ah4 ,hydrocarbons from animals petroleum1 asphalt1 amber1 etc4 #ai4 ,phosphates from animals guano1 phosphate rock1 etc4 ,talus ,where weathering is very active1 especially on or below steep mountain slopes1 a mass of loose1 angular fragments accumulates4 ,this material is termed talus1 a term which refers only to the physical character of the material1 and not at all to its composition4 ,if weathering continues these fragments will be further broken up into one of the finer grained rocks1 which the water can carry away and deposit elsewhere4 ,there is little or no layering in talus4 ,if the talus is not carried away but is cemented where it was formed1 the resulting mass is termed breccia1 but this is not very commonly the case4 ,breccia ,pl4 #eh ,the term breccia is used to cover all those rocks which are composed of angular fragments1 of any composition1 and above sand in size1 when they are cemented into a solid mass1 by any sort of cementing agent4 ,here the term is used in its broad sense1 as compared with the way it was used under igneous rocks4 ,breccias may result from the cementing of talus1 but more often the breaking up of the material into angular fragments was due to other causes1 such as crushing along a fault plane1 or in the movements involved in mountain making4 ,in such cases the breccia is of limited extent1 but may occur repeatedly in the same neighborhood4 ,limestone1 which has been crushed and then recemented1 often makes a rock which takes a good polish and is used in several localities as an ornamental stone in place of marble1 in fact often goes in trade circles under the name of 8marble40 ,the breccia figured on ,plate #eh is such a limestone4 ,soil ,over most of the earth's surface there is a covering of rock waste1 the product of weathering1 some of which is unassorted1 and some of it sorted by water or wind4 ,this is all termed soil4 ,it is an ever-moving cover resulting from the decomposition of the underlying rocks1 to which have been added in places layers of rock waste brought from afar by the streams4 ,some soils are rock waste which had been carried clear to the ocean and deposited on the floor of the sea1 and is now above sea level1 because the floor of the sea has been elevated4 ,inasmuch as the underlying rocks vary in composition1 and as there are areas of transported material1 it is clear that the composition of soils must vary from place to place1 both as to composition and texture4 ,soils range from the finest1 composed mostly of clay1 to coarse ones1 composed of sand1 gravel or even boulders4 ,clay1 the finest grained soil1 is composed of particles only about _/th of a millimeter in diameter1 of which it would take #gbj1jjj billion particles to make a gram's weight4 ,ordinary soils however have about #b to #e million particles to the gram4 ,the average specific gravity of soil with the usual amount of humus in it is from #b4ee to #b4ge4 ,in this case however the specific gravity is of less importance than is the volume weight4 ,a cubic foot of water weighs #fb pounds1 that of soil from #ge to #hj pounds1 the extremes being #cj lb4 for peaty soil and #aaj lb4 for calcareous sand4 ,the terms 8heavy0 and 8light10 used in agriculture do not refer to the volume weight1 for clay which is actually relatively light 7#gj-ge lb4 per cubic foot7 is classed as a 8heavy0 soil2 while sand1 of much greater actual weight1 is classed as a 8light0 soil4 ,these terms as used in agriculture refer to the ease with which the soils are worked1 and to their penetrability by plant roots4 ,soil is usually divided into an upper darker-colored layer1 termed loam1 and into a lower1 lighter-colored layer1 termed subsoil4 ,the presence of humus1 resulting from the decomposition of plant and animal remains is the factor which darkens the color and distinguishes the loam2 so that loam is a complex of inorganic rock particles plus more or less humus1 colloid compounds1 bacteria1 living plants and animals4 ,the subsoil is mainly rock particles4 ,the distinctions between these two layers break down in arid soils1 and often also in swampy regions4 ,it is this layer of soil on which the water of every rain and flood works1 picking part of it up and carrying it along1 step by step1 to the sea4 ,though the amount moved on any one day is small1 the sum of all the soil transported is enormous1 a large river carrying annual incredible amounts4 ,for instance the ,mississippi annually deposits in the ,gulf of ,mexico #dgf1ijj1jjj metric tons 7#bbjd lb4 to the metric ton71 of which about a third is in solution4 ,at this rate it takes about #gjjj to #ijjj years to remove a foot from over the whole drainage basin4 ,this is considerably slower than is the case of some other rivers4 ,while on the one hand soil is being continuously carried away from the surface1 on the other hand it is being constantly renewed from below1 by the weathering action of water1 air and temperature4 ,gravel ,gravel is a mass of loose fragments of rock1 which have been rounded by water and deposited with little or no sorting1 so that larger and smaller pebbles and sand all occur together4 ,it is the deposit laid down by comparatively fast water in inland lakes or along the storm-beaten shores of the sea4 ,where a swift stream enters quiet water1 as where it empties into a lake1 there it quickly drops its coarse material as gravel1 usually thus building a delta4 ,gravel also occurs in stream beds1 where for any reason the rate of flow is checked4 ,during the recent glacial period1 the ice sheet brought down great masses of unsorted material1 which was deposited as till1 or in moraines4 ,much of this was then picked up by the running water and moved longer or shorter distances1 so that1 all over the glaciated country of the northern and eastern ,united ,states1 there are unusually large numbers of gravel deposits4 ,gravels are all water laid1 and usually show more or less clearly the bedded or stratified structure4 ,the size of the component pebbles of gravel ranges from great boulders to fine sand1 and the finer gravels grade into the coarser sands1 the line between gravel and sand being drawn at about the size of a pea1 the coarser being gravel1 the finer sand4 ,gravel is widely used as ballast for railroads and in making highways1 because of its tendence to pack well1 while the hard pebbles resist wear4 ,it is also widely used in concrete work1 bonding in well with the cement1 and making it go from three to five times as far4 ,conglomerate ,pl4 #eh ,conglomerates are composed of rounded pebbles and sand of varying sizes1 cemented together into a solid rock4 ,the pebbles may run up to boulders in size1 but they have all been more or less rounded by water1 and transported some distance4 ,the pebbles may all be of the same composition1 or may represent a variety of rocks4 ,when the pebbles are all1 or most all1 of one sort1 the resulting conglomerate is termed a quartz-conglomerate1 a limestone-conglomerate1 a gneiss-conglomerate1 etc4 ,so too the cementing material varies in kind1 silica1 calcite and iron oxide being the commonest4 ,the color will depend on both the component pebbles and the cement1 sometimes one dominating1 sometimes the other4 ,there are some of the quartz- and limestone-conglomerates which can be cut and polished to make very handsome stone4 ,conglomerates represent consolidated gravels1 and always indicate an aqueous origin1 quite often the delta of an ancient stream1 or the invasion of the sea over the land2 so they have become of importance to geologists in interpreting past events4 ,sand ,sand is a mass of small rock particles1 from the size of a pea down to _/ of an inch in diameter4 ,the material may be any sort of rock1 or a mixture of two or more kinds4 ,sand may be the result of the disintegration of older rocks at the point where it is now found1 in which case the grains have the shapes they had in the original rock2 but more often the sand grains have been transported greater or lesser distances1 and in the process have been more or less rounded4 ,those sands1 which lie where they were formed are called residual1 and such sand is usually composed of a mixture of angular grains1 some harder and others softer1 such as quartz1 feldspar1 mica and hornblende1 all mixed together4 ,where the sand has been transported1 only the more resistant minerals have remained1 such as quartz1 magnetite1 cassiderite1 etc42 with which there are at times rarer minerals1 such as gold1 platinum1 garnets or topaz4 ,such sands are known as gold-bearing1 topaz-bearing1 etc4 ,the sands from different localities differ greatly4 ,the streams gather the rock particles1 and sort them according to the size1 which the water flowing at any given rate can carry4 ,when the water is slowed down1 it drops all the particles above the size which the new rate of speed can handle4 ,the grains of sand from the bed of a stream are usually more or less angular4 ,the further they are carried1 the more they are knocked together and rounded2 so that after being carried to the sea1 and then thrown up on the beaches1 they have been well rounded1 especially the larger grains4 ,as the air is less viscid than the water1 sand which is transported by the wind1 is even more rounded2 so that desert sands show the most complete rounding1 indeed are even polished2 and this is true even of the smaller grains4 ,it is the wind-blown1 or desert sands1 which flow so evenly in an hourglass4 ,between the angular residual sands and the polished desert sands1 there are of course all grades4 ,glacial sands are angular or 8sharp0 almost to the degree characteristic of residual sands2 and lake-shore sands are between river sands and sea sands in the degree of rounding4 ,sands made of particles of lime1 calcareous sands1 are less resistant to wear than are those of quartz4 ,in regions where the water is 8soft0 7free from lime71 they do not last long1 as they are dissolved2 but in a limestone region where the water is 8hard0 7saturated with lime71 the grains are not so quickly dissolved and may accumulate into beds of great thickness1 as in ,florida4 ,along some shores of the ocean1 there occur 8green sands10 which are ordinary quartz sands mixed with the dark green mineral glauconite1 which is a potassium iron silicate1 forming on the ocean bottom as a result of the action of decaying animal matter on iron-bearing clays and potassium-bearing silicates1 like feldspar4 ,this is particularly characteristic of some of the sands along the coast of ,new ,jersey4 ,in places1 especially in the beds of rivers1 there occur 8quicksands40 ,this is a deposit of fine sand1 mixed with a considerable amount of clay1 and saturated with water2 so that it will not support the weight of a man or an animal4 ,much that goes under the name of quicksand is a fluid mud1 covered with a thin layer of sand4 ,sand is used for a wide variety of commercial purposes1 and under these conditions gets various trade names2 for instance 8glass sand0 is a pure1 colorless to white1 quartz sand1 which is used as one of the components in making glass4 ,it must be free from impurities1 as these color the glass1 and much of the sand used for this purpose is quartz1 crushed to a fine sand-like condition4 8,moulding sand0 is a rather fine-grained quartz sand1 with a small but very definite admixture of clay1 and this is used to make the moulds for castings in foundries4 8,polishing sand0 is one composed of angular fragments of quartz1 usually from stream beds or glacial deposits1 or even crushed quartz1 and is used for cutting and polishing marble1 for sandpaper1 and for polishing wood and softer stones4 ,there are many other special uses1 like building1 ballast1 filters1 furnaces1 etc41 in which quartz sand is used1 being screened if necessary to get the right sizes4 ,sandstone ,when sand of any sort is cemented so as to make a solid rock1 it is termed sandstone1 which varies widely according to the size1 color and composition of the grains1 and also with the sort and amount of the cement4 ,when the size of the grains is larger than that of a pea1 sandstone grades into conglomerate2 when smaller than _/th of an inch1 especially if mixed with clay1 it grades into shale4 ,there are all grades of firmness1 due to the amount and kind of cement1 ranging from those which have little or no cement1 but are compact as a result of the pressure of the overlying rocks1 to those in which the cement has filled all the pore spaces4 ,in general there is a considerable amount of space between the grains of sand2 so that a sandstone will absorb large amounts of water1 up to #be of its bulk4 ,in moist climates where it freezes1 this makes many sandstones unsuitable for use as building stones1 as they are likely to spale1 or chip off1 as is seen in the 8brown stone0 so much used in ,new ,york ,city4 ,sandstones are usually bedded rocks and are relatively easy to quarry1 and most of them are not so firmly cemented1 but that they can be readily worked or cut into shape by the stone cutter2 and so1 certain sandstones are very popular for building stone or for trimming on buildings1 where they are not too much exposed to the weather4 ,sandstone gets a variety of names according to the cement4 ,siliceous sandstone is cemented with silica and usually very hard4 ,calcareous sandstone is cemented with lime and usually rather soft4 ,ferruginous sandstone is cemented with one of the iron oxides4 ,argillaceous sandstone is held together with clay impurities1 and is usually both soft and of undesirable color4 ,according to their composition there is also a number of varieties4 ,arkose is a sandstone composed of quartz and feldspar grains1 usually derived from the disintegration of granite and not transported far4 ,graywacke is a sandstone composed of quartz1 feldspar1 and some other mineral1 like hornblende-augite1 etc41 also derived from the disintegration of granites and not transported far4 ,grit is a term applied to a coarse sandstone1 composed of angular quartz fragments1 and used to a considerable extent for millstones4 ,flagstone is a thin bedded sandstone1 often with mica1 which splits easily and uniformly along the bedding planes2 so that it can be quarried in large slabs4 ,it was widely used for sidewalks before the advent of concrete4 ,freestone is a thick-bedded sandstone1 not over hard1 so called1 because it can be worked freely and equally well in all directions4 ,clay ,clay is a term used to describe a mass of fine particles1 the most prominent property of which is plasticity when wet4 ,clays range from masses of pure kaolin to masses of kaolin and related minerals mixed with as much as #fj of impurities1 which may be sand1 lime1 iron oxides1 etc4 ,the particles of a fine clay range around _/ of a millimeter in diameter1 while the impurities may be1 and usually are1 of larger size1 up to the size of sand grains4 ,all clays are of secondary origin1 the result of weathering1 especially of feldspars1 though clays may also result from the weathering of serpentines1 gabbros1 etc4 ,in some cases after the weathering of feldspar or limestones1 the clay may remain just where it was formed1 as a residual deposit2 but1 being so fine-grained1 it is usually transported by rain water or by the wind and deposited somewhere else as a sedimentary bed4 ,the quiet waters of a lake are favorable places for such deposits1 and many clay beds represent former lake bottoms4 ,impure clays are often laid down on the flood plains of sluggish streams4 ,in fresh water the settling of the clay is a very slow process1 requiring days1 or when very fine1 weeks1 before the water wholly clears4 ,in salt water1 however1 the clay sort of coagulates1 the particles gathering together in tiny balls1 which settle rapidly1 so that the water is soon clear4 ,according to their mode of origin clays are classified as residual1 sedimentary1 marine1 swamp1 lake1 flood-plain1 eolian1 etc4 ,but when their uses are considered a very different classification is made1 based mostly on their composition1 and we speak of ,china clays or kaolins1 fire or refractory clays1 paving-brick clays1 sewer-pipe1 stone-ware1 brick1 gumbo and slip clays4 ,the kaolin or china clays are residual clays1 usually resulting from the decomposition of pegmatite dikes4 ,they must be white when burned1 free from iron oxides1 and fairly plastic4 ,a good deal of china clay is made by crushing feldspar4 ,ball clays are sedimentary clays which remain white when burned1 are usually very plastic1 and free from iron oxides4 ,they are mostly used in the making of various sorts of china4 ,fire clays may or may not have iron oxides in them1 but they must be free or nearly free from fluxing materials1 such as lime1 magnesia and the alkalies 7sodium and potassium compounds74 ,they may be more or less plastic1 the essential quality being their ability to withstand high temperatures without fusing4 ,silica 7as sand7 tends to diminish the refractory quality2 so that a clay otherwise suitable1 if it has sand in it1 becomes at best a second grade fire clay4 ,in coal mining sections it is customary to term those beds of clay either above or below the coal1 8fire clay02 but this is an unfortunate designation1 for though some of them are true fire clays1 the most of them are not4 ,stone-ware clays are those with considerable sand and up to five per cent of fluxing materials4 ,they must be plastic enough to be readily worked1 and then burn to a dense body at comparatively low temperatures4 ,sewer-pipe clays must be plastic1 and carry a considerable amount of fluxing material1 as the surface of the pipe is expected to vitrify in the burning4 ,brick clays are low grade clays and vary greatly in composition4 ,the main requisites are that they mould easily and bake hard at relatively low temperatures with as little warping and cracking as possible4 ,as most clays shrink both in the air drying and in the baking1 sand is added when the clay is being mixed4 ,the color is mostly due to the presence of iron impurities4 ,if there are iron oxides and little or no lime1 the brick bakes to a red color1 but if there is an excess of lime over the iron oxides1 it bakes to a cream or buff color1 which on vitrifying turns green4 ,paving-brick clays range from surface clays1 to semirefractory clays1 shale being often used4 ,the essential component is enough fluxing material1 so that the bricks shall begin to vitrify1 or fuse1 at not too high temperatures4 ,slip clays are those with a high percentage of fluxing material2 so that1 when baked at moderate temperatures1 the surface fuses into a glassy brown or green glaze4 ,adobe is an impure calcareous clay1 widely used in the western ,united ,states for making sun-dried bricks4 ,gumbo is a term applied to fine-grained plastic clays which shrink too much in the burning to be useful in manufactures4 ,they can be burned to make an excellent ballast for railroads and highways4 ,they are especially abundant in the ,middle ,western ,states4 ,loess ,this is the name given to a fine grained homogeneous clay-like material1 which is a mixture of clay1 fine angular fragments of sand1 flakes of mica and more or less calcareous matter4 ,it is usually without stratification1 and cleaves vertically1 so that1 when eroded1 it forms steep cliffs4 ,loess covers great areas in the ,mississippi ,valley1 in the ,rhine ,valley1 and in ,north ,central ,china4 ,by some it is thought to be an accumulation of dust in those regions where the prevailing winds were of diminished velocity and where the grass or other vegetation has served to catch and hold the material2 by others it is thought of as a river and lake deposit2 and by still others it is thought to be due to the combination of the two modes1 wind and flood4 ,the writer inclines to the first view expressed4 ,shale ,pl4 #ei ,when pure or impure clays1 or loess1 are consolidated1 they are all grouped under the name shale4 ,it usually possesses a layered or stratified structure1 which makes it possible to split it into thin layers4 ,of all the sedimentary rocks shale is the commonest1 and it may occur in all the places where clay could occur1 but the most widely distributed shale is that which made the sea bottom of former times and is more or less calcareous1 like the piece on ,plate #ei1 in which bits of shells are still visible4 ,shale has the same wide variation in composition as has clay1 the various types being designated according to the impurity which is present1 as3 argillaceous shale1 made mostly of clay1 arenaceous shale1 shale with more or less sand as an impurity1 calcareous shale1 or one with more or less lime as an impurity1 ferruginous shale1 or one with iron compounds as impurities1 bituminous shale1 or one colored black by the presence of organic matter1 remains of either plants or animals4 ,while of no value as building material1 shale may be ground or crushed1 and used as a substitute for any corresponding clay1 and thus many manufacturers use shale in making fire-clay products1 bricks1 tile1 etc4 ,marl ,where limestones or shells of any sort have been pulverized1 and mixed with more or less impurities1 especially clay1 the resulting unconsolidated mass is known as marl4 ,it is usually associated with marine formations1 and is the finer dbris which has settled on the ocean bottom well out from shore1 that is out beyond the sandy and mud deposits4 ,finding it therefore usually indicates a sea bottom recently elevated4 ,it is very characteristic of the southern coastal states1 from ,maryland all along to ,texas4 ,limestone ,any mass of marl1 or aggregate of calcareous shells1 corals1 etc41 which has become consolidated is known as limestone4 ,it may1 and usually does1 have a wide range of impurities1 chief of which are clay1 sand1 iron oxides1 and bituminous matter1 like plant or animal remains4 ,pure limestone is white1 but due to impurities it ranges through grays1 greens1 browns1 to black1 and even red1 but this last is rarer4 ,it is easily identified by the presence of calcium carbonate1 which effervesces in hydrochloric acid4 ,it most often represents deposits in fairly deep water on ocean bottoms of the past1 but there is also a wide range of limestones which were formed in fresh water4 ,limestone is often burned at temperatures just above #ijj ,c1 at which point carbon dioxide goes off as a gas1 and leaves calcium oxide1 or lime4 ,when this is mixed with water it makes calcium hydroxide1 or slaked lime1 which is mixed with sand to give it body1 and is used as mortar4 ,when exposed to the air1 the slaked lime gives up water1 and takes back from the air carbon dioxide1 and again becomes calcium carbonate with its original hardness4 ,limestone is also used as one of the elements in all cements4 ,it is also considerably used as a building stone1 which1 however1 suffers in moist climates from the solution of its lime by rains1 but has stood up very well in dry climates4 ,the varieties of limestone are mostly distinguished according to their mode of origin1 some of them being as follows4 ,bog ,lime is a white calcareous powdery deposit on the bottom of ponds in limestone regions1 a deposit precipitated from solution by the action of the plants inhabiting the ponds4 ,coquina 7,plate #ei7 is the rock formed by the rather loose consolidation of shells and shell fragments4 ,it is particularly characteristic of tropical regions1 and is very abundant near ,st4 ,augustine1 ,fla41 in which region it was1 and still is1 cut into blocks and used for building stone4 ,in that mild climate it has stood very well4 ,chalk 7,plate #fj7 is a soft fine-grained limestone1 formed in the ocean by the accumulation of myriads of the tiny shells of ,foramenifera1 which are single celled animals1 living either a floating life near the surface of the sea1 or a creeping life on the bottom4 ,chalk is composed mostly of the shells of floating ,foramenifera1 which when the animals died1 settled to the bottom and there accumulated1 mostly at depths of #fjj feet or more4 ,when the mass of unconsolidated shells is dredged up from depths of #ej to #bjjj fathoms1 it is known as ,foramenifera ooze4 ,chalk beds are then indications of an uplifted sea bottom4 ,when consolidated1 if pure or nearly so1 it makes a white chalk1 and the beds may be of considerable thickness1 as is the case of the famous cliffs near ,dover on either side of the ,english ,channel4 ,one of ,huxley's most famous lectures is the one on chalk1 found in his ,essays and ,lay ,sermons4 ,coral ,rock is made by the cementation of fragments of corals4 ,the binding material1 as in most stones1 is lime2 and this sort of rock is associated with coral reefs of either the past or the present4 ,one of the best illustrations of this being the 8,dolomite ,mountains0 in ,tyrol4 ,coral rock1 like coquina1 has been cut into blocks and used as building stone1 as in ,bermuda4 ,encrinal ,limestone 7,plate #fj7 is a rock made by the cementation of fragments of the skeleton of crinoids4 ,these animals belong to the group1 echinoderms1 and are now extinct except for a few so called 8sea-lilies40 ,they were animals with a central mouth surrounded by long1 jointed1 flexible arms in multiples of five1 and below this a small body inclosed in calcareous plates1 all at the top of a long jointed stem4 ,they lived in the sea and in the earlier geological times must have been very abundant2 for their remains are so common in places as to make whole layers of limestone4 ,hydraulic ,limestone is a fine-grained1 compact1 yellowish limestone with from #ac to #ag of sand1 and some clay2 which1 when it is burned at a temperature a little higher than that used in burning lime1 makes a product1 that1 while not as strong as ,portland cement1 still like it sets under water4 ,lithographic ,limestone is a very fine-grained1 compact limestone with clay impurities1 the finest of the grain making it usable for making the stone plates used in lithographic printing4 ,on slabs of this limestone figures are drawn in reverse with a special crayon4 ,then the slab is treated with acid1 those parts which are not protected by the drawing being etched away1 while the points protected by the drawing remain in low relief4 ,from this slab figures can then be printed4 ,travertine is a general name1 applied to calcareous deposits from fresh water lakes or streams1 and has been precipitated either as a result of cooling or evaporation4 ,some travertines are porous1 while others are dense2 some are white1 while others are colored1 often beautifully1 by impurities in the water4 ,porous deposits of travertine1 when made on grass or other like substances1 are known as tufa or calc sinter4 ,such masses are common around ,caledonia1 ,n4 ,y41 ,mammoth ,hot ,springs in the ,yellowstone ,park1 etc4 ,onyx marble is a dense travertine1 usually formed as a result of the deposition of lime from the water of springs4 ,it is often banded1 due to the presence of impurities in the water at one time1 and their absence at other times4 ,till ,till is an unconsolidated mass of boulders1 pebbles1 sand and fine clay1 the unsorted material left behind by glaciers when they melted4 ,the boulders and pebbles1 while they show some wear1 are not rounded like those that have been transported by streams1 but have a more or less angular shape2 and some of them are polished or striated on one side1 where1 while frozen in the ice1 they were rubbed along the bottom4 ,one of the most recent geological events in ,america was the extension of the ice sheet1 now covering ,greenland1 down over north and northeastern ,north ,america1 until it extended as far south as northern ,new ,jersey1 the ,ohio ,river and the ,missouri ,river1 and as far west as the ,rocky ,mountains1 but not over the ,great ,basin1 the ,cascade ,ranges or ,alaska4 ,this great mass of ice1 thousands of feet thick1 moved from two centers1 one either side of ,hudson ,bay1 scraping up the loose soil1 and grinding off the exposed surfaces of the underlying rock4 ,all this material it carried southward1 until the melting along its lower margin equaled the rate at which it advanced4 ,when the melting was faster than the advance the glacial sheet retreated4 ,at the southern limit of the advance this dbris was dropped1 either making long ridges 7moraines7 or while the ice was retreating1 thicker or thinner sheets4 ,this deposited dbris is till4 ,the soil1 and especially the subsoil1 in all the regions formerly covered by the ice sheet1 is made up very largely of this till2 which1 where it is undisturbed is often called 8hardpan40 ,when till is mixed with humus it becomes loam4 ,this mixture of material1 varying all the way from the fine powdered products of the ice grinding to the great boulder it picked up and carried south1 is characteristic of this or any other glaciated country4 ,when this section of country was settled1 the boulders and stone were a hindrance to cultivation1 and were picked up and piled into stone walls1 which are one of the first features to strike the eye4 ,tillite ,when till is consolidated into solid rock1 it is known as tillite4 ,in several cases it has been found buried far beneath the more recent sedimentary rocks2 testifying that there were other glacial periods beside the last one which furnished the till4 ,the ,coal ,series ,disregarding minor constituents1 the plants are largely made up of cellulose1 which is a combination of carbon1 hydrogen1 and oxygen1 7,c,h,o74 ,if this is heated in the air1 where there is plenty of oxygen1 it disintegrates1 or burns1 making carbon dioxide and water2 but if the heating is done where the oxygen is excluded1 as in a kiln1 the hydrogen and oxygen will be driven off and the carbon will remain behind as charcoal4 ,in ,nature similar reactions go on1 but more slowly4 ,vegetable matter1 exposed to the air1 disintegrates into carbon dioxide and water1 and there is no solid residue4 ,however1 if the vegetable matter is under water1 which excludes the air more or less completely including the oxygen in it1 then disintegration still takes place1 but the products formed are water1 7,h,o7 marsh gas 7,,ch71 and some carbon dioxide 7,,co71 but a considerable part of the carbon remains behind and accumulates4 ,thus in bogs1 swamps and ponds1 where dead vegetation1 especially that growing in the water1 piles up1 the oxidation is incomplete2 so that there gradually accumulates on the bottom a layer of brown to black mud1 known as peat4 ,more plant remains are constantly being added1 and the layer may increase to several feet in thickness4 ,the decomposition is incomplete and some oxygen and hydrogen remain1 but the carbon is in a constantly increasing ratio and in proportion far above that in cellulose4 ,in the cold northern climates sphagnum moss is the most efficient peat producing plant1 but in temperate and tropical climates the moss is replaced by the leaves1 twigs1 trunks1 etc41 of trees1 bushes1 and vines4 ,if these peat beds are buried beneath a layer or layers of sediment1 especially clay1 the peat is sealed up and oxidation stops almost entirely4 ,with the pressure of the superincumbent beds1 the peat becomes more and more compact1 and changes to a dark-brown or black color4 ,it is then known as lignite4 ,if this lignite is buried still deeper1 with consequently more pressure and more time1 it changes into the still denser black bituminous coal4 ,this is as far as it will go unless some new agent is added to the forces already working4 ,the next step in the series of changes forming coal is associated with mountain making4 ,in case the layers of rock containing beds of coal are folded1 and that presupposes at least a moderate increase in heat1 the bituminous coal is altered to anthracite1 which is still denser1 and so hard that it breaks with a conchoidal fracture4 ,alteration may be carried a step still farther1 in case the rocks between which lie beds of coal are effected by such high temperatures as accompany metamorphism4 ,then all the associated hydrogen1 oxygen and moisture are driven off1 and only the carbon remains1 which is then known as graphite4 ,all steps between the stages especially designated occur4 ,the following represent steps only in the series of changes4 ,peat ,peat is a mass of unconsolidated vegetable matter1 which has accumulated under water1 and in which the original plant remains are still1 at least in part1 discernible4 ,it contains a large amount of water1 so that before it can be used as a fuel1 it is cut out in blocks1 which are piled up and left for a time to dry before using4 ,it burns with a long flame and considerable smoke4 ,this country is so well supplied with other fuels1 that so far peat has been but little used4 ,lignite brown coal ,lignite is more compact than peat1 and is found buried to some depth under layers of clay or sandstone4 ,it is dark brown to black in color1 and still retains pretty clear traces of the plants from which it was derived4 ,it also usually contains a considerable amount of moisture1 and when this is dried out1 it tends to crumble badly1 so that it is undesirable to handle it much1 or to ship it far1 before using4 ,it has a fair fuel value and is fairly widely used2 but it is very desirable that some method be found1 by which lignite could be treated to obtain its by-products1 and at the same time make it more compact1 so it would not crumble with the handling incident to using it in furnaces4 ,there are extensive lignite deposits in this country in ,north and ,south ,dakota1 ,montana1 ,wyoming1 ,colorado1 ,new ,mexico1 ,texas1 ,louisiana1 and ,mississippi4 ,bituminous ,coal soft coal ,this type of coal is compact1 black in color1 and breaks readily1 but does not crumble as badly as lignite4 ,it contains considerable water1 and still has some hydrogen and oxygen compounds in it4 ,bituminous coal is the product of plant remains which have been preserved for long periods1 7millions of years71 sealed from the air by the overlying beds of rock4 ,the pressure has made it compact1 and nearly all traces of the original plants have disappeared4 ,bituminous coal is our most abundant fuel1 occurring the world over in seams from less than an inch in thickness to some over fifteen feet thick4 ,the ,united ,states is peculiarly fortunate in the abundant and easily accessible deposits of this type of coal1 in ,pennsylvania1 ,west ,virginia1 ,ohio1 ,kentucky1 ,tennessee1 ,indiana1 ,illinois1 ,michigan1 ,iowa1 ,missouri1 ,kansas1 ,nebraska1 ,texas1 ,utah1 and ,colorado4 ,the volatile constituents1 hydrogen and oxygen compounds1 of bituminous coal may be driven off by heating the coal in closed ovens1 and the residual mass is known as coke1 almost pure carbon4 ,this is distillation1 and the ovens in which this is done1 without trying to save the volatile products1 are called bee-hive ovens1 while the more modern ovens which save the by-products are called by-products ovens4 ,a ton of bituminous coal treated in the typical by-products oven1 will yield on the average #adaj lb4 of coke1 #g4a gallons of tar1 #ah4i pounds of ammonia sulphate1 etc41 #b4d gallons of light oils1 #ajddj cubic feet of illuminating gas1 about half of this last being used to furnish the heat for the distillation4 ,the coal-tar dye industry is built on the tar thus produced4 ,toluol1 benzol1 etc41 come from the light oils2 and half the gas produced is available for household illumination1 etc4 ,coke is demanded1 as it is a superior fuel for melting iron ores1 iron and steel1 and is made regardless of whether the by-products are used4 ,the coke thus produced is hard1 clean1 and vesicular2 but for some reason as yet unknown1 by no means all bituminous coal will produce a coke which has this porous structure4 ,these latter are known as 8non-coking10 and are of little use to the steel industry4 ,cannel ,coal ,this is a compact variety of non-coking bituminous coal1 with a dull luster and a conchoidal fracture4 ,it contains the largest proportion of volatile hydrocarbon compounds of any variety of coal2 so that when the supply of petroleum and natural gas gives out1 this will be one of the important sources of obtaining substitutes4 ,cannel coals occur in ,ohio1 ,indiana1 and eastern ,kentucky4 ,this cannel coal owes its peculiar fatty nature to the material from which it is derived1 it being supposed to have resulted from the accumulation of the spores of lycopod trees1 and their conversion to jelly-like masses by bacteria in the fresh-water marshes of those ancient days4 ,anthracite hard coal ,anthracite coal is hard1 black1 has a luster1 and breaks with a conchoidal fracture4 ,it contains but a low percentage of volatile matter1 and so burns with a short flame1 and less smoke1 than is the case with the other coals4 ,it is always associated with folded rocks1 and appears to have been formed as a result of the combined pressure and the higher temperatures1 which accompanied mountain making4 ,still the temperature was not high enough to metamorphose the adjacent rocks4 ,most of our anthracite comes from northeastern ,pennsylvania4 ,carbonite ,carbonite is natural coke4 ,it occurs in coal seams which have been cut by dikes or intrusions of igneous rocks1 the coal having been thus coked by natural processes4 ,it is not vesicular like artificial coke1 for which reason it is not useful as a fuel4 ,some carbonite is found in the ,cerillos coal field of ,new ,mexico1 in ,colorado1 and ,virginia4 ,jet ,jet is a dense variety of lignite1 a fossil wood of black color1 which takes a high polish and cuts easily into various ornamental shapes4 ,it has been used for ornaments since early ancient times1 beads of jet being found in the early bronze period in ,england1 the supply probably coming from the ,yorkshire coast1 whence the principal supply comes even to the present day4 ,in ,switzerland and ,belgium it was used still earlier1 even as far back as the ,palolithic age4 ,jet seems then to have had a talismanic value1 and to have been worn to protect the owner4 ,about #gjj ,a4,d4 crosses and rosaries began to be made of jet1 the custom starting at ,whitby ,abbey1 the material being obtained nearby1 so that it came to be known as 8,whitby jet10 and in the eighteenth century became very popular4 ,in recent times it has been used mostly as jewelry suitable for mourning4 ,amber ,pl4 #fa ,amber is a gum which oozed from coniferous trees and was petrified4 ,it is associated with lignite beds of middle ,tertiary age4 ,it is usually pale-yellow in color1 but at times has a reddish or brownish tinge1 and is more or less transparent4 ,it occurs in rounded irregular lumps1 up to ten pounds in weight1 though most pieces are smaller2 and is mostly picked up along certain coasts where it is washed ashore by the waves4 ,since the earliest records amber has been cast up on the shores of the ,baltic1 and it was used by peoples as early as in the stone age for ornaments and amulets4 ,it has been found among the remains of the cave dwellers of ,switzerland1 in ,assyrian and ,egyptian ruins of prehistoric age1 and in ,mycen in the prehistoric graves of the ,greeks1 the first recorded reference to it being in ,homer1 and the ,greek name for amber being elektron from which our word electricity comes4 ,all these finds were of ,baltic amber which was doubtless gathered and traded by those early men4 ,even down to the present many men make their living1 riding along the shore at low tide and hunting for the amber washed ashore by the waves4 ,as early as #ahfj the ,german geologists concluded that the source of the amber must be lignite beds outcropping beneath the sea level1 and started mining for the amber with fair success1 so that today two types of ,baltic amber are distinguished1 8sea stone0 which is washed ashore1 and 8mine stone0 taken from the mines4 ,beside the ,baltic locality1 it is found along the shores of the ,adriatic1 ,sicily1 ,france1 ,china1 and occasionally of ,north ,america4 ,some pieces of amber are found with insects inclosed and preserved almost as perfectly as if collected yesterday4 ,they were apparently entangled in the gum while still viscid and completely embedded1 before fossilization4 ,the ,petroleum ,series ,certain sedimentary rocks contain larger or smaller quantities of natural gas1 petroleum1 mineral tar and asphalt4 ,these are compounds of carbon and hydrogen1 or hydrocarbons1 and range from gases to solids1 each being a mixture of two or more hydrocarbon compounds4 ,the crude petroleum may have either a paraffin base or an asphalt base3 in the former case1 when the gas1 gasoline1 kerosene1 etc41 have been removed by distillation1 the solid residue will be paraffin1 as in most of the ,pennsylvania crude oils2 while in the latter case1 the solid residue will be an asphalt1 as in most of the ,california and ,texas crude oils4 ,in the case of the paraffin series all the compounds belong to the paraffin group1 while the asphalt is due to the presence1 in addition to the paraffin group1 of some of the benzine series of hydrocarbons4 ,petroleum is found in sands and shales1 which were originally deposited on ancient sea bottoms1 the shales generally being the real source of the petroleum4 ,the oil was once the fatty portion of animal bodies 7perhaps to some extent of plant bodies71 and was separated during decomposition as a result of bacterial activity4 ,oil thus produced is in tiny droplets1 which have a great affinity for clay4 ,after being freed by the bacteria1 the oil droplets in muddy water attach themselves to particles of clay1 and as the clay settles the oil is carried down with it1 the two eventually making a bituminous shale4 ,in clear water1 or in water which is in motion1 the oil droplets rise to the surface and eventually distill into the air4 ,the oil1 or petroleum1 may stay diffused through the shales1 in which case we have oil-bearing shales1 with sometimes as much as #bj of oil4 ,were there but _/ of a per cent of oil in a layer of shale #aejj feet thick1 this would amount to #gej1jjj barrels per square mile which is equal to a rich production from wells4 ,when the oil in shale amounts to three per cent or more1 it is commercially usable4 ,there are large stretches of petroleum-bearing rocks in ,new ,york1 ,pennsylvania1 ,ohio1 ,indiana1 and all the way out to the ,pacific coast1 some of them with oil so abundant1 that a blow of the hammer will cause them to smell of petroleum4 ,in case these oil-bearing shales have been heavily overburdened and compressed1 the petroleum may have been more or less completely pressed out of them4 ,then the droplets uniting have formed a liquid1 which has moved out from the shale1 and gone wherever it could find open spaces4 ,sandstones have frequently offered their pore space1 and as it filled1 have been thus saturated with petroleum4 ,if the sandstones were open to the air1 or if fissures extended from them to the surface1 the oil has escaped to the surface and evaporated into the air4 ,but in those cases where the sandstone 7or other permeable rocks7 was covered by an impervious layer1 like a dense shale or clay1 the oil was confined below the covering layer of rock4 ,crude oil is lighter than water2 so that when natural gas1 petroleum and water were all present in the rocks1 the gas lies on top1 the petroleum next1 and the water underneath4 ,with this in mind it is easy to see1 that in slightly folded or undulating layers of rock1 the gas and petroleum would be caught under upraised folds and domes4 ,this is the basis of prospecting for oil4 ,if petroleum-bearing layers are depressed far enough beneath the surface to be affected by the high temperatures of the earth's interior1 or have been near volcanic activity1 of course the petroleum has been distilled by natural processes1 and at most only the residues1 like paraffin or asphalt1 have remained4 ,for this reason it is impossible to find petroleum in igneous or metamorphic rocks4 ,natural gas ,natural gas is the lightest portion of crude oil1 and consists mostly of marsh gas 78fire damp10 ,,ch7 together with other light hydrocarbons1 like ethane 7,c,h71 ethylene 7,c,h71 and some carbon dioxide and monoxide4 ,it is colorless1 odorless1 and burns with a luminous flame4 ,mixed with air it is explosive4 ,it is found in sedimentary rocks1 mostly sandstones1 either with or without petroleum4 ,usually it is under considerable pressure1 and escapes with great force wherever a hole permits4 ,in time the gas all escapes through the hole or well1 and then the well 8runs out40 ,if petroleum is present under the natural gas1 the hole may become an 8oil well10 from which petroleum may be pumped1 until it in turn is exhausted4 ,the end of an oil supply is usually indicated by the appearance of water in the well4 ,natural gas is mostly associated with oil districts1 as in ,pennsylvania1 ,ohio1 ,illinois1 ,texas1 ,california1 etc4 ,petroleum ,crude ,oil ,pl4 #fa ,petroleum is a mixture of paraffin compounds all the way from the gases1 through gasoline1 kerosene1 lubricating oils1 and vasoline to paraffin4 ,in some of the crude oils there is also an admixture of compounds from the benzine series1 in which case1 when all the volatile compounds have been distilled off1 an asphalt remains4 ,the different components of petroleum may be separated out by heating the crude oil in closed tanks1 and drawing off the various substances at the proper temperatures4 ,petroleum occurs in sedimentary rocks of marine origin1 usually rocks which also contain the shells of some of the animals1 the soft parts of which made the oil4 ,to have been preserved the millions of years since the petroleum was first formed1 the oil-bearing layers must have been covered by some impervious layer of rock1 beneath the domes and anticlines of which the oil has lain ever since4 ,when such a dome or anticlinal fold is perforated by a well1 the released oil flows to the surface with a greater or less rush1 according to the pressure4 ,wells may keep flowing for #bj years1 sometimes more1 sometimes much less4 ,those which flow with the greatest pressure usually are relatively short lived1 at times lasting only a year or two4 ,when this easily obtained oil is exhausted1 there is an even greater supply to be obtained by the distillation of the bituminous shales4 ,petroleum never occurs in igneous or metamorphic rocks1 but is found in either sandstones or shales1 in places favorable for accumulation1 all across that great stretch of ancient sea bottoms1 extending from the ,appalachian ,mountains to the ,rocky ,mountains1 and in the ,great ,basin between the ,rocky ,mountains and the ,sierra ,nevada ,range1 and also to the west of the ,sierras4 ,bitumen ,where petroleum has escaped through pores in the rocks1 or by way of fissures1 and has come to the surface of the earth1 the lighter components1 thus exposed to the air1 have vaporized and escaped1 leaving behind a more or less solid residue1 which is known as bitumen4 ,if the escape was through a fissure1 the bitumen may have accumulated in the fissure until it was filled1 making vein bitumen4 ,or the escape may have been so rapid that the petroleum formed a pool or lake from the surface of which evaporation took place4 ,in time such a pool will give off the gases and volatile compounds1 only a residue remaining to make a pitch lake1 like the one at ,rancho ,le ,brea near ,los ,angeles1 or an asphalt lake like the one on the island of ,trinidad4 ,on account of their varying hardness and composition1 some of these bitumens have received special names2 as3 ,albertite1 a black bitumen with a brilliant luster on broken surfaces1 a hardness between #a and #b1 and a specific gravity a shade over #a4 ,grahamite1 a black bitumen1 which is brittle1 but has a dull luster1 a hardness of #b1 and a specific gravity of #a4ae4 ,gilsonite or ,uintaite1 a black bitumen with a brilliant luster and a conchoidal fracture1 a hardness of #b to #b1 and a specific gravity of #a4jf4 ,malta is a semi-liquid viscid natural bitumen1 which has a considerable distribution in ,california4 ,the above varieties of bitumen look a good deal like coal1 but are easily distinguished by their lightness 7weight about half that of coal71 and the fact that with only moderate heat they melt1 and become a thick liquid like tar4 ,guano ,guano is the accumulation of the excrement of birds 7or of other animals like bats7 on areas so dry that1 though soluble1 it is not leached and washed away4 ,it may also contain some of the bones and mummified carcasses of the birds which died on the spot4 ,the greatest of these deposits are on several small islands1 just off the west coast of ,peru1 and now 8farmed0 by the ,peruvian government4 ,in this country there are no true guano beds1 except a few accumulations of bat guano in certain caves of ,kentucky and ,texas1 but these are not large enough to become of commercial importance4 ,phosphate ,rock ,phosphate rock is one composed chiefly of calcium phosphate along with various impurities1 such as clay and lime4 ,it occurs in beds1 irregular masses1 or as concretionary nodules in limestone or sand4 ,the bedded varieties are in the older sedimentary rocks1 in which the phosphate runs from a small percentage up to as high as #he4 ,ultimately the phosphate came from either animal excrement1 or from bacterial decomposition of animal carcasses and bones4 ,in all the beds it seems to be true that in the first instance the phosphate was laid down as a disseminated deposit in marine beds1 usually limestones4 ,later by the action of water leaching through the rocks1 the phosphate was dissolved1 and then redeposited elsewhere in a more concentrated form4 ,this may be either in the underlying sandstones1 but is more often in limestones1 replacing the original lime4 ,in these secondary deposits1 if the phosphate has been laid down in cavities1 the resulting phosphate will be in nodular masses4 ,in the case of the ,florida and ,carolina deposits1 these nodules have been freed from their matrix and washed along the river beds1 remaining as pebbles in the river sands4 ,the bed deposits are mostly in ,kentucky and ,idaho4 ,the commercial use for such phosphate rocks is of course the making of fertilizers4 ,diatomaceous ,earth ,pl4 #fb ,diatoms are tiny single-celled plants living in uncounted millions in the fresh and salt water4 ,each diatom builds around itself two shells which fit into each other like the cover and box of a pill-box1 and each shell is marvelously ornamented4 ,the shells are composed of silica of the opal type4 ,in size the diatoms range from _/ of an inch in diameter up to the size of a pin head1 and they live in such numbers that ordinary surface waters have hundreds of them to the quart1 and where they are flourishing up to #bej1jjj in a quart4 ,when the plants die1 or in order to reproduce abandon the shells1 these shells fall to the bottom of the pond or the sea1 and there accumulate1 often making a layer from a few inches thick up to hundreds of feet in extreme cases4 ,if unconsolidated1 this mass of tiny shells is known as diatomaceous earth2 but if they are consolidated it is called tripolite1 so named because the first of them used commercially came from ,tripoli4 ,as the shells are tiny and uniform in size and have a hardness of #f1 the diatomaceous earth is used to make a great variety of polishes1 scouring soaps1 tooth paste1 as a filler in certain kinds of paper1 in making waterglass1 as an absorbent for nitroglycerine1 and as packing in insulating compounds1 where asbestos would otherwise be used4 ,deposits of freshwater diatoms are found all over the ,united ,states1 usually in thin layers of limited extent1 especially in ,massachusetts1 ,new ,york1 ,michigan1 etc4 ,the marine deposits of diatoms are on a much larger scale1 there being beds of diatoms in ,anne ,arundel1 ,calvert and ,charles ,counties1 ,md41 up to #be or #cj feet in thickness4 ,in ,santa ,barbara ,county1 ,cal41 there is one bed #bdjj feet thick and another #dgjj feet thick1 beside many other smaller ones4 ,the enormous former wealth of life indicated by these great deposits may be suggested1 when it is remembered that it takes about #abj1jjj1jjj to make an ounce in weight4 ,they reproduce on an average about once in five days1 so that from a single diatom the offspring possible under favorable conditions would amount to over #af1jjj1jjj in four months or over #fj tons in a year4 ,of such an order is the potential increase of animals or plants1 no matter how small1 if the rate of reproduction is high4 ,metamorphic ,rocks ,either a sedimentary or an igneous rock1 which has been altered by the combined activities of heat1 pressure and chemical action1 becomes a metamorphic rock4 ,the process is essentially one1 during which the layers of rock come under the influence of such temperatures as are associated with the formation of granite or lavas4 ,such material as is actually melted becomes igneous rock1 but adjacent to the masses actually melted are other rocks which do not melt but1 according to the temperature1 are more or less changed1 and these are the metamorphic rocks4 ,at a distance from the molten masses the changes are minor1 but close to the molten magmas extensive changes take place4 ,though not actually melted the rock near the heat center may be softened1 usually is1 in which case pebbles and grains or even crystals become soft and plastic1 and1 as a result of the great pressure1 are flattened1 giving the rock1 when it cools again1 a striated appearance4 ,at these high temperatures the water in the rock and also some other substances vaporize1 and the hot steam and vapor are active agents in making a great many chemical changes4 ,in some cases material like clay is changed into micas1 or chlorite1 etc42 in other cases the elements of a mineral will be segregated and large crystals will appear scattered through the metamorphic rock1 such as garnets1 staurolites1 etc4 ,if one studies a layer of rock both near and far from the molten mass1 all grades of change will appear4 ,for example1 at a distance a conglomerate maybe unaltered2 somewhat nearer the molten mass1 the heat and steam may have softened 7but not melted7 the pebbles and then the pressure has flattened them as though they were dough2 and nearest the molten mass1 the outlines of the pebbles are lost1 only a layered effect remaining1 and many of the materials have changed into new minerals1 like mica1 garnets1 etc41 but still the layered effect is preserved4 ,one of the effects of heat and pressure is to flatten the component particles of the rock1 so that it tends to split in a direction at right angles to the direction of the pressure1 just as particles of flour are softened and flattened under the pressure of the roller2 and then when the crust is baked it splits or cleaves at right angles to the direction in which the pressure was exerted by the roller4 ,this tendency to split is not to be confused with either the layering1 characteristic of sedimentary rocks1 nor the cleavage characteristic of minerals4 ,it has nothing to do with the way the particles were originally deposited1 nor with their cleavage2 but is due to the pressure1 and resembles the pie crust splitting1 being irregular and flaky4 ,this is designated schistosity if irregular and slaty cleavage if regular4 ,schistosity refers to the flaky manner of splitting into thin scales as in mica schists4 ,slaty cleavage is more regular1 this being due to the fact that the material of which slate is made is small particles of clay of uniform size4 ,the metamorphic rocks are generally more or less folded1 as they are always associated with mountain making4 ,these major folds are of large size1 from a hundred feet across to several miles from one side to the other4 ,such folds may also occur in sedimentary rocks or even in igneous rocks and simply express the great lines of yielding1 or movement of the crust of the earth4 ,in addition to this there is minor folding or contorting which is characteristic of metamorphic rocks only4 ,when the rocks were heated by their nearness to the molten igneous magmas1 they must expand1 but being overburdened by thick layers of other rocks1 there is no opportunity for yielding vertically1 so the layers crumple1 making minor folds from a fraction of an inch to a few feet across4 ,such crumpling1 which is so very conspicuous especially where there are bands of quartzite in the rock1 is entirely characteristic of metamorphic rocks4 ,it is seen on hosts of the rocks about ,new ,york ,city1 all over ,new ,england1 and in any other metamorphic region4 ,plate #fc is a photograph of such a crumpled rock which has been smoothed by the glacial ice4 ,the metamorphic rocks are the most difficult of all the rocks to determine and understand1 because the amount of change through which they have gone is greatest1 but for this same reason they offer the most interest1 for the agents which caused the changes are of the most dramatic type of any that occur in ,nature4 ,from one place to another a single layer of metamorphic rock changes according to the greater or less heat to which it was subjected1 making a series of related rocks of the same composition but with varied amount of alteration4 ,for this reason in naming metamorphic rocks1 a type is named1 and from that there will be gradations in one or more directions1 both according to composition1 and according to amount of heat involved4 ,if it is possible to follow a given layer of metamorphic rock from one place to another this is of great interest2 for by this means1 many variations in the type will be found1 both those resulting from a different amount of heat1 and those due to the local changes in the composition of the original rock4 ,one further consideration has to be kept in mind4 ,when a rock is metamorphosed the high temperatures either drive off all water1 or the water may be used up in the making of some of the complex minerals4 ,when such a metamorphic rock later comes near the surface and is exposed to the presence of ground water1 and that leaching down from the surface into the rocks1 several of the minerals formed at high temperatures will take up this water and make new minerals such as serpentine1 chlorite1 etc4 ,they are always associated with metamorphic rocks1 and have been metamorphic rocks1 but since then have become hydrated1 forming minerals not at all characteristic of high temperature4 ,the following shows the relation of the sedimentary and igneous rocks to their metamorphic equivalents4 ,loose sediment ,consolidated sediment ,metamorphic equivalent gravel conglomerate gneiss sand 7quartz7 sandstone quartzite mud 7sand and clay7 shale schist clay shale slate or phyllite marl limestone marble peat bituminous coal anthracite to graphite coarse igneous rocks such as gneiss granite1 syenite1 etc4 fine igneous rocks such as schist trachite1 rhyolite1 etc4 ,in working out the past history of any given region1 much of it is done on the basis of this series of equivalents4 ,the finding of limestone1 for instance1 indicates that the given area was at one time under the sea to a considerable depth1 that is from #ajj to #ajjj feet1 but not ocean-bottom depths which run in tens of thousands of feet4 ,marble indicates the same thing1 and so one can go on through all these types of rock4 ,gneiss ,pl4 #fd ,gneiss is an old word used by the ,saxon miners1 and is often very loosely used4 ,here it is used in its structural sense1 and a gneiss may be defined as3 a banded metamorphic rock1 derived either from a sedimentary or an igneous rock1 and is composed of feldspar1 quartz1 and mica or hornblende1 and is coarse enough1 so that the constituent minerals can be determined by the eye4 ,it corresponds to a granite1 or some sedimentary rock like gravel or conglomerate4 ,due to the action of pressure1 all the gneisses are banded1 and the original constituent particles or crystals are distorted4 ,the lines of banding may be long or short1 straight1 curved or contorted4 ,when the banding is not conspicuous1 the gneiss tends toward a granite4 ,when the banding is thin and the structure appears flaky1 the gneiss tends toward a schist4 ,the color varies according to the constituent minerals1 from nearly white1 through red1 gray1 brown1 or green to nearly black4 ,plate #fd shows one gneiss which is in a less advanced stage1 the pebbles being simply flattened and the matrix partly altered to micaceous minerals1 and a second gneiss which is so far advanced that the original constituents are all altered to other minerals and only the banded structure remains4 ,this latter type would have required but little more heat to have completed the melting and changed this to a granite4 ,gneisses are very compact and have little or no pore space in them4 ,they are hard and strong and resist weathering well1 so that they are widely used as building stone3 but they are not as good as granite for this purpose1 as they split more readily in one direction and can not therefore be worked so uniformly as can granite4 ,there are many varieties of gneiss1 based either on their origin1 composition1 or their structure1 as follows3 ,granite-gneiss is one derived by metamorphism from granite4 ,syenite-gneiss is one derived by metamorphism from syenite4 ,diorite-gneiss is one derived by metamorphism from diorite4 ,gabbro-gneiss is one derived by metamorphism from gabbro4 ,biotite-gneiss is one composed of quartz1 feldspar and biotite4 ,muscovite-gneiss is one composed of quartz1 feldspar and muscovite4 ,hornblende-gneiss is one composed of quartz1 feldspar and hornblende4 ,banded-gneiss is one in which the banded structure shows clearly4 ,foliated-gneiss is one in which there is thin irregular layering4 ,augen-gneiss is one which has concretionary lumps scattered through it4 ,gneisses have a wide distribution over all ,new ,england1 most of ,canada1 the ,piedmont ,plateau1 the ,lake ,superior region1 the ,rocky ,mountains1 the ,sierra ,nevada and the ,cascade ,ranges4 ,quartzite ,quartzite is metamorphosed sand or sandstone1 and frequently grades into one or the other4 ,it is a hard compact crystalline rock1 which breaks with a splintery or conchoidal fracture4 ,it is distinguished from sandstone by the almost complete lack of pore spaces1 its greater hardness and by its crystalline structure4 ,in practice it may be distinguished by the fact that a sandstone in breaking separates between the grains of sand1 while a quartzite breaks through the grains4 ,some quartzites are almost pure quartz1 but others contain impurities of clay1 lime or iron1 which were in the original sandstone4 ,these alter in the metamorphism to such accessory minerals as feldspar1 mica1 cyanite1 magnetite1 hematite1 calcite1 graphite1 etc4 ,the color of quartzite when pure is white1 but may be altered to red1 yellow1 or green by the presence of these accessory minerals4 ,on account of the difficulty of working the quartzites1 they are not much used in building1 though they are very durable4 ,when crushed they often make excellent road ballast1 or filling for concrete work4 ,the pure varieties are sometimes ground and used in the manufacture of glass4 ,according to the accessory mineral1 the following varieties may be distinguished2 chloritic-quartzite1 micaceous-quartzite1 feldspathic-quartzite1 etc4 ,quartzites are common in the ,new ,england1 the ,piedmont ,plateau1 and ,lake ,superior metamorphic regions1 and also in many western localities4 ,schist ,pl4 #fe ,schist is a loosely used term1 but is used here in its structural sense4 ,it includes those metamorphic rocks which are foliated or composed of thin scaly layers1 all more or less alike4 ,the principle minerals are recognizable with the naked eye4 ,in general schists lack feldspar1 but there are some special cases in which it may be present4 ,quartz is an abundant component of schists2 and with it there will be one or more minerals of the following groups3 mica1 chlorite1 talc1 amphibole or pyroxene4 ,frequently there are also accessory minerals present1 like garnet1 staurolite1 tourmaline1 pyrite1 magnetite1 etc4 ,all schists have the schistose structure1 and split in one direction with a more or less smooth1 though often irregular1 surface4 ,at right angles to this surface they break with greater or less difficulty and with a frayed edge4 ,as they get coarser1 the schists may grade into gneisses1 losing their scaly structure3 while on the other side1 as the constituent minerals become finer and so small as to be difficult of recognition1 schists may grade into slates4 ,the varieties of schist are based on the mineral associated with the quartz2 as mica-schist1 chlorite-schist1 hornblende-schist1 talc-schist1 etc4 ,the color also is due to the constituent minerals other than quartz and ranges widely1 mica-schists being white to brown or nearly black1 chlorite-schists some shade of green1 hornblende-schists from dark green to black1 talc-schists white1 pale-green1 yellowish or gray1 etc4 ,schists are found all over the same regions as gneisses and quartzites1 i4e41 ,new ,england 7especially good exposures of schist being seen about ,new ,york ,city71 the ,lake ,superior region1 ,rocky ,mountains1 etc4 ,beside these regions where it occurs native1 there are boulders of schist all over the glaciated areas of eastern and northern ,united ,states4 ,slate ,slate is a metamorphic rock which will split into thin or thick sheets1 and is composed of grains so fine as to be indistinguishable to the unaided eye4 ,the cleavage is the result of pressure during metamorphism1 and has nothing to do with the bedding or stratification of the sedimentary rock from which it was derived4 ,the original bedding planes may appear as streaks1 often more or less plicated1 and running at any angle with the cleavage4 ,if these bedding streaks are abundant or very marked1 they may make a slate unsuitable for commercial uses4 ,the slaty cleavage may be very perfect and smooth so that the rock splits into fine sheets1 in which case it is often used for roofing slate2 but by far the greater part of the slates have a cleavage which is not smooth or perfect enough so that they can be so used4 ,slates are the metamorphic equivalents of shales and muds1 and represent the effect of great pressure but with less heat than is associated with schists or phyllite1 and consequently with less alteration of the original mineral grains4 ,the color ranges from gray through red1 green and purple to black4 ,the grays and black are due to the presence of more or less carbonaceous material in the original rock1 the carbon compounds having changed to graphite4 ,the reds and purple are due to the presence of iron oxides1 and the green to the presence of chlorite4 ,while the particles of slate are so small as to be indistinguishable to the unaided eye1 the use of thin sections under the microscope shows that slate is composed mostly of quartz and mica1 with a wide range of accessory minerals1 like chlorite1 feldspar1 magnetite1 hematite1 pyrite1 calcite1 graphite1 etc4 ,according to their chief constituents slates may be distinguished as argillaceous-slate or argillite1 bituminous-slate1 calcareous-slate1 siliceous-slate1 etc4 ,slate will be found here and there in the metamorphic areas of ,new ,england1 the ,piedmont ,plateau1 the ,lake ,superior region1 and in many places in the west4 ,phyllite ,pl4 #ff ,phyllite is a thinly cleavable1 finely micaceous rock of uniform composition1 which is intermediate between slate and mica schist4 ,in this case the flakes of mica are large enough to be distinguishable to the eye1 but most of the rest of the material can only be identified with the aid of a microscope4 ,it is mostly quartz and sericite4 ,phyllite represents a degree of metamorphism greater than for slate1 but less than for schist2 and it may grade into either of these other rocks4 ,garnets1 pyrite1 etc41 may be present as accessory minerals4 ,the color ranges from nearly white to black1 and it is likely to occur in the same places as do slates4 ,marble ,pl4 #ff ,this is a broad term1 and includes all those rocks composed essentially of calcium carbonate 7limestones7 or its mixture with magnesium carbonate 7dolomite71 which are crystalline1 or of granular structure1 as a result of metamorphism4 ,it takes less heat to metamorphose a limestone1 and for this reason the marbles have a more crystalline structure than most metamorphic rocks2 and they do not have the tendency to split or cleave which is so characteristic of most metamorphic rocks4 ,it is only when there is a large amount of mica present that the typical schistosity appears4 ,commercially the term marble is used to include true marble and also those limestones which will take a high polish2 but in this book1 and geologically speaking1 no rock is a marble unless it has crystalline structure4 ,marbles range widely in color according to their impurities4 ,pure marble is white4 ,carbonaceous material in the antecedent limestone is changed to graphite in the metamorphic process1 and makes the marble black1 but appears usually in streaks or spots1 rather than in any uniform color4 ,an all black 8marble0 is usually a limestone4 ,the presence of iron colors the marble red or pink4 ,chlorite makes it green1 etc4 ,various accessory minerals are common in marbles1 such as mica1 pyroxene1 amphibole1 grossularite among the garnets1 magnetite1 spinel1 pyrite1 etc41 through a long list4 ,because it cuts readily in all directions and takes a high polish1 marble is widely used as a building stone4 ,in the moist climate of the ,united ,states it suffers in being soluble in rain water when used on the outside of a building3 but for interior decoration it furnishes some of the finest effects4 ,the largest marble quarries are developed in ,vermont1 ,massachusetts1 ,new ,york1 ,pennsylvania1 ,georgia1 ,alabama1 ,colorado1 ,california1 and ,washington4 ,steatite ,soapstone ,steatite is a rock composed essentially of talc1 which is associated with more or less impurities1 such as mica1 tremolite1 enstatite1 quartz1 magnetite1 etc4 ,it is found in and with metamorphic rocks1 and is a rock which has been modified by hydration from a metamorphic predecessor4 ,it was probably first a tremolite or enstatite schist1 in which1 after the metamorphic rock came into the zone where ground water exists1 the tremolite or enstatite was altered to talc1 the impurities remaining much as they were in the first place4 ,it is bluish-gray to green in color1 often soft enough to cut with a knife1 and has a greasy feel4 ,it is very resistant to heat and acids2 for which reasons it has proved very useful commercially in making hearthstones1 laundry tubs1 and fire backs2 and1 when powdered1 in making certain lubricants4 ,the ,indians1 in the days before ,columbus1 took advantage of the ease with which it is cut1 to make from it large pots for holding liquids1 which are today among the greatest treasures in collections of ,indian relics4 ,they also carved pipe-bowls and various ornaments and amulets from soapstone4 ,it is found in ,vermont1 ,massachusetts1 ,new ,york1 ,new ,jersey1 ,pennsylvania1 ,maryland1 ,virginia1 ,north ,carolina1 ,georgia and ,california4 ,serpentine ,pl4 #fg ,pure serpentine is the hydrated silicate of magnesium1 as described among the minerals on page #ach4 ,serpentine rock is serpentine with more or less impurities1 such as pyroxene1 amphibole1 olivine1 magnetite1 chromite1 calcite1 magnesite1 etc4 ,it often also contains mica and such garnets as pyrope1 as accessory minerals4 ,serpentine1 like steatite1 always occurs in and with metamorphic rocks1 and was originally a metamorphic rock1 but has since been changed by the hydration of its silicates1 when it came into the zone in which ground water is present4 ,in the first instance it was some sort of shale1 clay and dolomite1 which was metamorphosed to an amphibole or pyroxene schist4 ,when this was exposed to the action of ground water1 the amphibole or pyroxene minerals were changed to serpentine1 resulting in a rock composed mostly of serpentine1 but retaining the impurities which were in the metamorphic rock1 and perhaps adding to them such amphiboles and pyroxenes as were not altered during the hydration process4 ,the above is the commonest type of serpentine rock4 ,it can and sometimes has been formed in a similar way from an igneous predecessor1 by the hydration of its silicate minerals4 ,in this latter case the serpentine would not be a modified metamorphic rock1 but a modified igneous one4 ,it is a case where such a rock as a diorite or a gabbro is exposed to ground water and the pyroxene present altered to serpentine4 ,a serpentine formed in this way would be a very impure one4 ,serpentine rock is used as an ornamental stone for interior decoration1 because it takes a high polish and has pleasing colors1 various shades of green4 ,it is however decidedly soft and will stand very little exposure to weather1 and it is also filled with seams which make it difficult to get out large slabs4 ,serpentine rock occurs fairly commonly in the metamorphic belt of ,new ,england and the ,piedmont ,plateau1 and in some of the western states1 especially ,california1 ,oregon1 and ,washington4 ,ophiolite ,ophicalcite ,this name is given to marbles which are streaked and spotted with serpentine4 ,they are a mixture of green serpentine and a white or nearly white calcite1 magnesite or dolomite in variable proportions4 ,ophicalcite occurs in and with metamorphic rocks1 and represents an impure limestone which has been metamorphised1 the lime becoming marble1 and the impurities becoming such silicates as pyroxene1 amphibole1 or olivine4 ,this metamorphic rock has then come into the zone of ground-water and the silicate minerals have been changed by hydration to serpentine4 ,ophicalcite is then a metamorphic rock1 in which secondary chemical changes have since taken place4 ,it may have a wide range of accessory minerals present1 such as magnetite1 chromite1 pyrope among the garnets1 olivine1 etc4 ,verde antique is a trade name for one of the ophiolites4 ,while not abundant1 ophicalcite is in good demand as an ornamental stone for interior work2 for it takes a high polish1 and is beautiful2 but1 on the other hand1 it will not stand exposure to the weather for the calcite is soluble1 and there are numerous seams and cracks in it making it difficult to obtain large slabs4 ,it occurs in ,quebec1 ,canada1 in the ,green ,mountains of ,vermont1 and in the ,adirondack ,mountains4 ,,chapter ,v ,,miscellaneous ,,rocks ,there are a few rocks which do not fit into any of the three groups described1 such as concretions1 geodes1 meteorites1 etc41 and they are gathered together here4 ,there is also one type of rock1 which really belongs among the minerals1 but is likely not to be so recognized at first glance1 and that is the material filling veins4 ,these last are sometimes designated 8vein rocks10 but are really massive deposits of one1 two or more minerals1 and should be referred to the minerals when found4 ,concretions ,in the sedimentary rocks there frequently occur inclusions of a nature different from the surrounding rock4 ,in shape they are usually rounded1 nodular1 spherical1 discoidal1 ovate1 flattened1 elongated or ring-shaped1 or combinations of the foregoing1 making often curious and fantastic forms4 ,in size they range from a fraction of an inch in diameter to several feet through4 ,when broken1 they may show a nucleus1 around which more or less concentric layers have formed1 or neither nucleus nor concentric structure may be visible4 ,the layered structure of the surrounding rock in some cases continues right through the nodular mass4 ,these structures are called concretions1 and their formation in all cases is at least due to similar reactions4 ,in general the concretions differ from the surrounding rock in composition1 but are usually composed of some one of its impurities1 of lime in the clays or silica in limestones1 of iron oxide in sandstone1 etc4 ,they seem to have originated as a result of the solution of the minor mineral1 and then its redeposition around some center or nucleus4 ,in many cases the nucleus is organic1 such as a leaf1 a shell1 a bone1 etc41 so that when the concretion is split1 in its center will be found the perfect imprint of the leaf1 or the shell of a mollusk1 or a bone of a higher animal1 sometimes a whole skeleton4 ,again the nucleus may be inorganic like a grain of sand2 and in still other cases no nucleus can be found1 though there was probably one in the beginning4 ,what has happened is somewhat like the case of accessory minerals in igneous and metamorphic rocks4 ,a layer of sediment was laid down1 including in it1 here and there1 something foreign to the run of the rock4 ,later when the water leaches through this rock1 impregnated with lime for instance1 it comes to the point where a leaf is decomposing4 ,the products of the leaf decomposition are different from what is already present in solution1 and may precipitate some of the lime in that neighborhood4 ,as long as leaf decomposition continues the precipitation in that region will continue and increase the size of the concretion4 ,this sort of action accounts for many of the concretions1 especially those about organic remains4 ,in some other cases where there is no nucleus1 as the flint in chalk1 what has taken place is that the small amounts of silica in the lime have been dissolved1 and then around some center has constantly been added more and more non-crystalline silica until a mass of flint has accumulated4 ,there may be a considerable variety of ways to account for different concretions1 but in all cases solutions of one mineral have come in contact with solutions of a different kind1 and precipitation about a center has resulted4 ,clay stones ,pl4 #fh ,of all the concretions these are perhaps the commonest1 being found in the clays of all types and in many regions4 ,they are made of lime and precipitated around some nucleus of foreign matter4 ,the shapes vary widely1 usually discs1 flattened ovals or even rings1 in most all cases however flattened4 ,this is indicative of the water moving though the clay more freely in some layers than others4 ,often clay stones occur so abundantly that two or more have grown together making fantastic shapes1 sometimes resembling animals1 and all sorts of fancied but unrelated objects4 ,as the clay stones have grown the clay has not been pushed aside1 but has been incorporated within the concretion2 so that when a concretion is dissolved in acid1 it yields not only the lime1 which is its reason for being1 but also a large amount of clay4 ,claystones are found in clays most anywhere1 usually occurring in certain layers and being absent from others4 ,lime concretions ,these are found mostly in shales which carry a high percentage of clay as impurities1 and are characteristic of the older geological formations1 especially ancient sea bottoms4 ,they are likely to have as a nucleus some shell1 fish bone1 or a leaf1 which when the concretion is split1 reveals a wonderfully preserved portion of an animal or a plant1 which was buried millions of years ago4 ,the lime concretion is closely related to the claystone1 and is really a claystone which has been buried so long that the surrounding matrix has changed to a shale instead of remaining clay4 ,one of the most famous localities for these lime concretions is ,mazon ,creek1 ,illinois1 where thousands of these concretions have been picked up and split to study the organic remains included4 ,the commonest objects found are fern leaves1 like the one on ,plate #fh4 ,but about once in a thousand times they inclose a spider or insect1 and once in ten thousand times the skeleton of an amphibian1 which is of especial interest1 as here have been thus found the remains of the very earliest of the land animals4 ,these remains were inclosed in these concretions during the coal age1 probably #ej1jjj1jjj years ago1 and once inclosed all the hard parts have been as well preserved after that long interval1 as they were immediately after being inclosed in the concretion4 ,lime concretions range from less than an inch in diameter to several feet through4 ,they are not confined to shales1 but sometimes occur in sandstones1 in this case also usually having as a nucleus either a shell1 or the bone1 or bones1 of some animal4 ,they are likely to be found anywhere in the limestone belt1 from the ,appalachian ,mountains to the ,rocky ,mountains1 or in the ,great ,basin1 or on the ,pacific ,coast4 ,often they have been mistaken for turtles and other objects4 ,a good many of the cases where the head or body of animals 8petrified with all the flesh0 are reported1 it is one of these concretions which has a shape sufficiently like the part described1 for the imagination to construct the rest4 ,septeria ,pl4 #fi ,septeria are lime concretions1 which1 after they had formed1 have shrunk and developed a series of cracks running through them in all sorts of directions1 and since then the cracks have been filled with various minerals1 such as calcite1 dolomite1 and siderite4 ,these make a series of veins which intersect the concretion1 in a sort of network4 ,septeria are mostly of considerable size1 ranging from six inches in diameter to several feet through4 ,they are characteristic of the shales of ancient sea bottoms1 especially those of ,devonian age in ,new ,york1 and ,pennsylvania1 and those of ,cretaceous age in ,wyoming1 ,montana and the ,dakotas4 ,flint concretions ,the silica in limestones is often segregated into nodular masses of varying sizes1 to make concretions of flint4 ,such masses have grown in the limestone1 and1 while growing1 have either pushed away1 or dissolved the adjacent limestone1 so that the flint nodule is pure silica4 ,they are especially characteristic of the chalk beds1 and of ancient limestones which formed on the floor of the sea1 like the ,helderberg ,limestone of ,new ,york1 ,pennsylvania1 ,ohio1 etc4 ,when thin sections are cut through these flints1 and examined under the microscope1 many remnants of the shells of plants and animals are still recognizable4 ,a nucleus is seldom found1 but in some cases there is a fossil in the nodule about which the concretion doubtless formed4 ,the spicules of sponges1 shells of diatoms1 and of radiolarians seem to have contributed most of the material from which flint concretions are formed4 ,in addition to the silica there are frequently inclosed in these nodules the horny jaws of various sea worms1 and a host of spiny balls the relationships of which are still unknown4 ,sandstone concretions ,there are two types of sandstone concretions1 first those which are cemented with lime1 and second those cemented with iron oxide4 ,the concretions bound by lime are especially characteristic of sandstones which were laid down as river deposits1 either in the channels or on the flood plains1 and also the sandy deposits resulting from wind deposition4 ,in these cases the concretions will mostly be found to have formed around some organic nucleus1 most frequently about a bone1 or group of bones1 of some ancient animal4 ,in this country they are mostly found in the arid and semiarid sections of the ,west1 where the present day wind erosion exposes the harder parts of bluffs1 etc4 ,the second type of sandstone concretion is the one in which the cement is most often limonite1 less often hematite4 ,these concretions are less dense than the lime ones1 and in some cases the limonite is only precipitated at a distance from the nucleus1 which has resulted in the formation of a hollow shell1 filled with loose sand4 ,this is especially characteristic of certain concretions1 found in a gravel or coarse sand in the region of ,middletown1 ,del4 ,oolites ,in large bodies of water like the sea and some larger lakes we find concretions which have formed1 or are still forming1 about tiny grains of sand1 which are still being moved about by the waves and currents4 ,in such cases not only are great masses of concretions formed but they have very clearly marked the concentric layering1 which shows that they have increased in size1 sometimes more rapidly and sometimes more slowly4 ,where great masses of such concretions have formed the resulting rock appears like a great mass of small eggs1 whence the term oolite4 ,the cement may be any one of several substances1 but lime1 silica1 and hematite are perhaps the most common4 ,here and there are found larger or smaller masses of this oolite4 ,in some cases it would appear that the material was precipitated by the action of bacteria4 ,such for instance is probably the origin of the ,clinton iron ore1 a bed of oolitic hematite1 extending from ,new ,york ,state all down the ,appalachian ,mountains to ,alabama4 ,pisolite ,pl4 #fi ,when the concretions1 formed in exactly the same manner as in the case of oolite1 are of a size bigger than a pea1 then the rock is known as pisolite4 ,other ,concretions ,though less abundant concretion may form from still other substances4 ,hematite has been mentioned1 and when concretions are made of this material1 either they have been deposited by bacteria1 or were formed as limonite and the water of crystallization of this latter mineral driven off4 ,manganese concretions are found on the floor of the ocean at maximum depths1 and brought to the surface by dredging4 ,geodes ,geodes are nodules1 which1 when broken open1 are found to be hollow and the cavity lined with one or more minerals4 ,they represent a special case of minerals in a cave4 ,there was in the first place a cavity in the surrounding rock1 usually of sand or clay4 ,as the water leached through the surrounding rock1 it became saturated with one or more minerals and then coming into the cavity1 deposited the minerals1 either as crystals1 or as a non-crystalline mass1 lining the cavity4 ,thus the inside is often a beautiful cluster of bristling crystals1 or it may be simply layer on layer of chalcedony of any color4 ,before this process had gone so far as to completely fill the cavity1 erosion had dislodged the mass1 and it has been found4 ,one usually recognizes that it is a geode by the fact that it is far too light to be a solid rock1 and then it may be carefully broken4 ,they are characteristic of certain formations2 so that having accidentally broken the first one1 others can be carefully opened to display the beauty of the interior4 ,the geode illustrated on ,plate #gj is lined with quartz crystals1 but near by were found many others1 some of which had chalcedony and some jasper as a lining4 ,such crystallined nodules are usually called geodes so long as they occur in a softer matrix so that they are easily dislodged1 and until they reach a size of three or four feet in diameter4 ,pebbles ,when picked up either from brook beds1 sea beaches1 or the open plain1 there are few forms of rock which tell a story of the past more completely than do pebbles2 and any one1 who enjoys reading a story written in form1 structure and composition1 will find in pebbles one of the most satisfying and at the same time testing exercises4 ,the story may be complex or simple according to what has happened to the parent rock1 and to that is added what happened since the pebble left the ledge where it was a part of a great mass4 ,one must not forget to take into consideration where the pebble was found and the character of its associates4 ,this sort of exercise is recommended to all interested in rocks4 ,it will yield something upon first trying1 and more on prolonged study2 and the fullness with which it is done will test one's knowledge of the meaning of rocks as nothing else will do4 ,as a sample of this sort of exercise let us take the two pebbles illustrated on ,plate #ga4 ,the upper one is a common quartz pebble picked up in a ,new ,england brook bed4 ,such pebbles are common all over the country formerly covered by the glacial ice sheet4 ,it is crystalline quartz1 but the individual crystals are not distinguishable1 and such quartz is typical as the filling of veins4 ,it therefore goes back to a time when the rocks were fissured1 probably in connection with the folding accompanying mountain making far to the north in ,canada4 ,into the fissures thus formed seeped the water which had been leaching through the adjacent rocks1 and it was saturated with silica which it had dissolved from those rocks4 ,in the open fissure the quartz was deposited as crystals1 which grew finally filling the fissure and crowding each other so that all the faces were obliterated4 ,the quartz vein was complete1 but it must have been far below the surface of the ground4 ,time must have passed1 thousands of years of it1 until1 in the weathering away of the mountain system1 the many feet of overlying rock were removed and this vein was brought to the surface4 ,as the quartz is harder than the adjacent rocks1 the vein soon projected as a ledge4 ,the effect of changes of temperature in alternately expanding and contracting the rocks developed cracks1 into which water worked its way1 and then the breaking was hastened by the expansion which takes place when water freezes1 and in exposed regions is so effective1 because the freezing and thawing are so often repeated4 ,finally an angular fragment of quartz was dislodged and lay on the surface1 resistant to the solvent power of the rain4 ,in this case this happened just before the advance of the great ice sheet4 ,when that came to the place where the fragment lay1 it was picked up along with all other loose material and partly shoved in front of1 but probably mostly carried frozen in the ice1 and journeyed one1 two1 three hundred1 perhaps a thousand miles4 ,this took many years for the ice moved only a few feet a day4 ,finally however it came to the point where the ice melted as fast as it advanced1 and our quartz fragment was dropped at the front of the ice sheet along with other great masses of till4 ,here there was abundant water1 partly from the melting of the ice1 and partly from the storms which must develop where there are such contrasts in temperature1 as there would be over the ice1 on one hand1 and over the bare land in front of the ice on the other hand4 ,a torrent picked up our fragment and started it on a second journey1 banging against other stones as it rolled along down the stream bed1 every time it struck another stone bruising the corners which soon became rounded4 ,thus from time to time during high water the quartz fragment1 becoming rounder every time it moved1 journeyed down stream1 until it came to the point where the stream emptied into a lake4 ,here the current was checked and the stone dropped to the bottom along with other larger stones to make the delta at the mouth of the stream4 ,there it lay as long as the lake existed1 and would be lying now1 but that in ,new ,england a tilting movement of the land tipped the north end of the lake up and the water all ran out4 ,then the stream began to flow over its own delta and in time of freshet tore a channel down through the old delta carrying the pebble still further down1 until it came to the level stretch which represented the old lake's bottom and there it dropped the pebble in its bed4 ,and there it was found and picked up to become the pebble which told the above story of its life1 and to repeat it as often as anyone will look at it with a seeing eye4 ,the second pebble is quite a different one4 ,it was picked up in a gravel bank along a railroad cut1 just at the foot of ,mt4 ,toby in ,massachussetts1 and the writer has used it many times to test his students1 to see if they could read the story which it tells4 ,it consists of two sorts of rock1 the one1 angular fragments of a hornblende schist1 the other1 a fine-grained granite filling all the spaces between the fragments of schist1 even in cracks less than a quarter of an inch wide4 ,the schist is the older rock and in its first appearance represents a deposit of mud 7clay and sand7 on the floor of the ocean1 well out from the shore1 and somewhere off to the east of ,mt4 ,toby1 perhaps ten miles1 perhaps more1 from the place where it was found4 ,this was back in early ,palozoic times1 millions of years ago4 ,this deposit was buried by further layers of sediment on the sea bottom and cemented into a shale4 ,then during a mountain making period the region was folded1 and the sediments were altered by the combined pressure and heat1 our layer of rock becoming a hornblende schist4 ,after that happened considerable time must have passed1 but just how much is not indicated by the pebble1 before another period of disturbance took place1 during which this deep seated schist was faulted1 and shattered to fragments along the line of breaking4 ,this accounts for the angular fragments4 ,then into the fissure thus formed was pressed a molten magma1 which while liquid enough to flow and be squeezed into every opening could not have been very hot2 for not even the corners of the schist fragments are melted or altered1 so as to appear any different from the mass of the schist4 ,the molten magma cooled rather slowly1 making a fine-grained granite4 ,this must all have taken place far below the surface1 or the magma would have cooled into a felsite or dense lava4 ,again a long time must have elapsed1 while the rock overlying our piece was eroded away1 so it could come to the surface4 ,just about the time it did come to the surface1 the ,connecticut ,valley was formed by a great block1 #ie miles long by fifteen to twenty miles wide1 dropping down six or eight thousand feet 7probably not all at once but by one or two hundred feet at a time7 between two north and south faults4 ,this took place in the ,triassic ,period4 ,of course the streams then began to wash sand and stones of all sizes into the hole4 ,our pebble was one of these4 ,while still an angular fragment1 lying perhaps ten miles east of the ,connecticut ,valley1 a stream started it moving1 and as it rolled along the brook bed1 it was battered and rounded to its present shape1 and finally tumbled over a waterfall to the bottom of the great hole1 which had been formed as described above4 ,here with other stones it formed part of a coarse gravel1 coarsest near the sides of the hole1 and finer toward the middle2 for the material was further distributed in the bottom of the valley4 ,our stone stayed pretty near the side and was soon buried beneath hundreds of feet of similar material4 ,the leaching water dissolved enough iron rust so that this acted on the lower layers as a cement and bound the whole mass into a conglomerate4 ,here for some millions of years our pebble rested1 while above it was piled sand and gravel and a couple of sheets of lava1 until the hole was filled1 and our pebble was near the bottom of the mass4 ,later movements of the land raised the whole region1 fully six thousand feet1 and erosion went on for other millions of years4 ,the conglomerate and sandstone wore away faster than the metamorphosed rocks on either side of the filled valley1 so that a new valley1 the present ,connecticut ,valley1 came into existence4 ,when our pebble finally came near to the surface on the side of ,mt4 ,toby 7a mound of conglomerate which somehow was protected and wore down a little less rapidly than the conglomerate on either side of it71 it was just about the time of the glacial period4 ,the great ice sheet went over the mountain removing all the loose material and some more of the solid conglomerate4 ,this brought our pebble to the surface1 but too late to be moved by the ice4 ,however as soon as the ice left the ,mt4 ,toby region1 the rains fell1 and in the further weathering of the conglomerate1 the cement holding our pebble in place was dissolved and it was freed4 ,at once a tiny brook started it rolling down the side of the mountain1 a brook so small that when the pebble reached the foot of the slope it did not have power to carry it further4 ,here there gathered a fan-shaped mound of such pebbles1 known as an alluvial fan4 ,it rested here not over a couple of thousand years1 when the ,central ,vermont ,r4 ,r4 cut a groove through the fan1 using the material for ballast1 and here the pebble was found and brought home4 ,meteorites ,meteorites can hardly be called common1 but there is always a chance of finding one1 and their interest is so great1 that none should escape because unrecognized4 ,meteorites are visitors to the earth from space1 and they bring to us knowledge of the composition of planets and solar systems1 other than our own4 ,it is of interest to note1 that while they have brought to us some combinations of elements which do not occur in the earth1 still they have not brought any element with which we were not already familiar4 ,they are popularly known as 8falling0 or 8shooting stars10 though of course they are not stars1 but only small masses of matter which are entirely invisible until they come inside our atmosphere4 ,in space there are many small 7compared with the size of the earth7 chunks of matter1 each pursuing its solitary way around the sun1 or wandering through space along paths entirely unrelated to the sun4 ,from time to time one of these passes near enough to the earth1 so as to be influenced by its attraction1 and then comes rushing toward it at tremendous speed1 #bj to #cj miles per second4 ,as soon as it comes into the atmosphere1 even the very attenuated atmosphere1 a couple of hundred miles above the surface1 friction heats the surface of the meteor until it glows1 and by that light we see the so-called shooting star1 often with a trail of luminous matter streaming out behind4 ,of course in using this term 8shooting star10 we understand the meteor is no star1 for they are bodies as big as our sun1 shining at distances billions of miles away4 ,as the meteor rushes through the atmosphere it may all burn up1 no large fragment reaching the earth's surface4 ,the luminous matter streaming out behind is material which has melted and dripped off the main mass4 ,as this oxidizes and cools1 that part which did not become gaseous will finally fall to the earth as fine dust4 ,when however a meteor actually falls to the earth1 its surface is still hot1 though probably there has not been time enough for much heat to be transmitted to the interior4 ,at any rate they do not show any alteration due to this cause4 ,on landing and sometimes before they land meteors break into two or more pieces4 ,when found the surface always shows the effects of the heat generated by the friction of passing through the air1 the surface being smoothed1 and covered with stream lines and melted out pits and hollows1 and the outer surface consisting of a thin crust1 making an appearance1 which once seen1 can hardly be mistaken4 ,there are two types of meteorites1 those made wholly or largely of iron with some nickel1 and appearing like great chunks of iron1 and those which are stony and resemble a granite boulder4 ,in collections the first sort1 i4e4 iron meteorites1 are most abundantly represented1 because most easily recognized when found4 ,they consist of masses of iron and nickel with small amounts of other elements1 ranging in size from the ,cape ,york meteorite1 which fell in northern ,greenland in #ahid and was later brought by ,peary to the ,american ,museum1 and weighs some #cf tons1 down to small grains as small as a grain of wheat4 ,the largest one which has fallen in the ,united ,states was the ,willamette meteorite weighing some #ae tons1 and falling #ai miles south of ,portland1 ,oregon4 ,these and all iron meteorites have the iron in crystalline form which is readily seen if the meteorite is cut1 and the surface thus made polished1 then etched with acid1 which is put on and quickly washed off4 ,every meteorite has its particular pattern1 as illustrated on ,plate #gb1 and by these patterns can be identified4 ,meteorites have a high value and are eagerly sought by certain large institutions and collectors4 ,since the crystalline structure is so characteristic of each fall1 when a new meteorite is found1 it is usually cut in two1 and one part retained by the finder or some institution2 while the other part is cut into small pieces1 an inch or two on a side and a quarter of an inch thick1 but each large enough to show the characteristic pattern4 ,these are distributed largely by sale to other collectors4 ,thus a great meteorite collection consists of a few large meteorites and a great many small portions of other meteorites4 ,the second type of meteorite is the stony meteorite4 ,where meteorites have been located as they fell and recovered1 the majority of them were of this type1 so that probably more than half of the meteorites which fall are of the stony type4 ,however when the stony meteorite is exposed to weathering it takes only a very short time before the surface is eroded off and then such a meteorite looks like any other boulder and probably most of them fail to be recognized1 and so have been lost4 ,because they have so much greater variety1 they are in many ways of greater interest than the iron type4 ,it is desirable that every one have his eye out for meteorites1 and when found it is desirable that the fact should be reported to some one of the great institutions which collect them1 such as the ,national ,museum in ,washington1 or the ,american ,museum in ,new ,york4 ,each one should be on record even if it is desired to keep it in a private collection4 ,fossils ,in the sedimentary rocks one is apt to find remains of some of the animals and plants that lived at the time the rock was forming4 ,while the soft parts of animals decompose rapidly1 shells and bones are likely to be buried in the sediments1 and if the conditions have been favorable1 these remains may be preserved more or less perfectly4 ,all through the millions of years that sedimentary rocks have been forming in the sea1 in lakes1 on river flood plains and in wind swept deserts1 there was an abundance of life1 as much as there is today2 and our knowledge of that life is derived from these buried fossil remains1 so that fossils have a great historic interest4 ,however as there have lived and died several times as many different kinds of animals as live today1 the study of fossils becomes a separate subject1 which cannot be treated in this book4 ,should any collector of rocks and minerals come upon fossils1 he is opening a new field1 and it will be necessary to turn to other sources for their identification4 ,general books on this subject are scarce1 but one or two are given in the literature list4 ,a ,list of the ,elements1 the ,abbreviations ,used for ,them1 and ,their ,atomic ,weight1 ,which ,is ,approximately the ,number of ,times ,heavier ,they ,are ,than ,hydrogen4 ,name ,oxygen #af ,aluminium1 ,al #bg ,antimony1 ,sb #abb ,argon1 ,ar #dj ,arsenic1 ,as #ge ,barium1 ,ba #acg ,beryllium1 ,be #i ,bismuth1 ,bi #bji ,boron1 ,b #aa ,bromine1 ,br #hj ,cadmium1 ,cd #aab ,csium1 ,cs #acb ,calcium1 ,ca #dj ,carbon1 ,c #ab ,cerium1 ,ce #adj ,chlorine1 ,cl #ce ,chromium1 ,cr #eb ,cobalt1 ,co #ei ,columbium1 ,cb #ic ,copper1 ,cu #fd ,dysprosium1 ,dy #afb ,erbium1 ,er #afg ,europium1 ,eu #aeb ,fluorine1 ,f #ai ,gadolinium1 ,gd #aeg ,gallium1 ,ga #gj ,germanium1 ,ge #fc ,glucinum1 ,gl #i ,gold1 ,au #aig ,hafnium1 ,hf #agi ,helium1 ,he #d ,holmium1 ,ho #afe ,hydrogen1 ,h #a ,indium1 ,in #aae ,iodine1 ,i #abg ,iridium1 ,ir #aic ,iron1 ,fe #ef ,krypton1 ,kr #hd ,lanthanum1 ,la #aci ,lead1 ,pb #bjg ,lithium1 ,li #g ,lutecium1 ,lu #age ,magnesium1 ,mg #bd ,manganese1 ,mn #ee ,mercury1 ,hg #bja ,molybdenum1 ,mo #if ,neodymium1 ,nd #add ,neon1 ,ne #bj ,nickel1 ,ni #ei ,nitrogen1 ,n #ad ,osmium1 ,os #aij ,oxygen1 ,o #af ,palladium1 ,pd #ajg ,phosphorus1 ,p #ca ,platinum1 ,pt #aie ,potassium1 ,k #ci ,prseodymium1 ,pr #ada ,protoactinium1 ,pa #bca ,radium1 ,ra #bbf ,radon1 ,rn #bbb ,rhenium1 ,re #ahf ,rhodium1 ,rh #ajc ,rubidium1 ,rb #he ,ruthenium1 ,ru #ajb ,samarium1 ,sm #aej ,scandium1 ,sc #de ,selenium1 ,se #gi ,silicon1 ,si #bh ,silver1 ,ag #ajh ,sodium1 ,na #bc ,strontium1 ,sr #hh ,sulphur1 ,s #cb ,tantalum1 ,ta #aha ,tellurium1 ,te #abh ,terbium1 ,tb #aei ,thallium1 ,tl #bjd ,thorium1 ,th #bcb ,thulium1 ,tu #afi ,tin1 ,sn #aai ,titanium1 ,ti #dh ,tungsten1 ,w #ahd ,uranium1 ,u #bch ,vanadium1 ,v #ea ,xenon1 ,xe #aca ,ytterbium1 ,yt #agc ,yttrium1 ,y #hi ,zinc1 ,zn #fe ,zirconium1 ,zr #ia ,table of ,geologic ,time ,eras ,periods and their ,important ,physical ,important ,duration in ,millions ,events ,organic ,events of ,years ,cenozoic ,quaternary ,recent ,youthful land forms ,dominance of man4 having high relief formed4 ,pleistocene ,epoch #b ,m4,y4 ,period of ,heidelberg1 glaciation2 four ,neanderthal1 and great ice advances4 ,cr-,magnon man2 extinction of large mammals4 ,tertiary ,pliocene ,epoch #aj ,m4,y4 ,continuing ,intermigration of world-wide land ,north and ,south elevation4 ,american mammals4 ,transformation of ape to man4 ,miocene ,epoch #ah ,m4,y4 ,cordilleras1 ,alps1 ,culmination of ,himalayas formed4 modern types of ,widespread mammals4 ,apes vulcanism-basalt appear in ,old flows in ,world4 northwestern ,united ,states4 ,oligocene ,epoch #aj ,m4,y4 ,land dominant2 seas ,carnivores and marginal4 ungulates develop into importance4 ,eocene ,epoch #bj ,m4,y4 ,extensive ,dawn of the sedimentation2 seas dominance of marginal4 mammals4 ,reptiles subordinate4 ,cretaceous #fe ,m4,y4 ,widespread ,climax and epicontinental culmination of seas4 ,laramide reptiles1 revolution at close especially of period--,rocky dinosaurs2 first ,mountains formed4 flowering plants and grasses4 ,mesozoic ,jurassic #ch ,m4,y4 ,continent emergent2 ,rise of birds and shallow seas on flying reptiles1 western ,north first modern ,america4 trees4 ,triassic #ce ,m4,y4 ,continent emergent2 ,rise of seas marginal4 dinosaurs1 cycads1 and ammonites4 ,paleozoic ,permian #ce ,m4,y4 ,world-wide ,extinction of continental uplift most ,paleozoic and mountain fauna and flora4 building4 ,first modern ,widespread insects4 glaciation4 ,pennsylvanian #dh ,m4,y4 ,continent ,great alternately rising coal-forming and sinking4 forests1 of ferns and seed-ferns4 ,mississippian #ce ,m4,y4 ,low lands and ,culmination of widespread crinoids1 submergence4 numerous sharks4 ,devonian #dj ,m4,y4 ,widespread ,first known land submergence1 local animals1 first vulcanism4 forests4 ,silurian #bh ,m4,y4 ,widespread ,first lung fishes submergence1 local and scorpions1 deserts4 abundant corals4 ,ordovician #fe ,m4,y4 #fj of ,north ,climax of ,america below sea4 invertebrate dominance1 first vertebrate4 ,cambrian #aje ,m4,y4 ,widespread ,first abundant submergence4 invertebrate fauna1 trilobites dominant4 ,proterozoic #gjj ,m4,y4 ,long periods of ,bacteria and granite intrusion1 seaweeds present4 sedimentation1 and ,most mountain building4 invertebrates probably present1 but remains are lacking4 ,archeozoic #hjj ,m4,y4 ,world-wide ,blue-green algae intrusive igneous present1 activity2 some primitive sediments4 one-celled plants and animals probably present4 ,,bibliography ,,mineralogy ,getting ,acquainted with ,mineralogy4 ,by ,g4 ,l4 ,english1 #aicf1 ,mc,graw-,hill ,book ,co4 ,a beginning textbook of mineralogy4 ,introduction to the ,study of ,minerals and ,rocks4 #crd ,edition1 by ,a4 ,f4 ,rogers1 #aicg1 ,mc,graw-,hill ,book ,co4 ,describes the commoner minerals systematically4 ,dana's ,textbook of ,mineralogy4 #dth ,edition1 revised by ,w4 ,e4 ,ford1 #aicb1 ,john ,wiley and ,sons4 ,detailed descriptions of minerals1 their physical properties1 and their occurrence4 ,manual of ,mineralogy4 #aeth ,edition1 by ,e4 ,s4 ,dana1 revised by ,c4 ,s4 ,hurlburt1 #aida1 ,john ,wiley and ,sons4 ,a textbook of mineralogy4 ,,mineral ,,economics1 ,,geopolitics ,world ,minerals and ,world ,peace4 ,by ,c4 ,k4 ,leith1 ,j4 ,w4 ,furness1 and ,cleona ,lewis1 #aidc1 ,the ,brookings ,institution4 ,physical1 economic1 and political trends in the mineral industry4 ,minerals in ,world ,affairs4 ,by ,t4 ,s4 ,lovering1 #aidc1 ,prentice-,hall4 ,minerals ,yearbook4 ,u4 ,s4 ,bureau of ,mines4 ,an annual volume presenting statistical data on the production of the mineral resources of the ,united ,states4 ,reports on individual minerals or rocks may be had separately4 ,,economic ,,geology ,mineral ,deposits4 #dth ,edition1 by ,w4 ,lindgren1 #aicc1 ,mc,graw-,hill ,book ,co4 ,the manner of occurrence and origin of mineral deposits4 ,elements of ,engineering ,geology4 #bnd ,edition1 by ,h4 ,ries and ,t4 ,l4 ,watson1 #aidg1 ,john ,wiley and ,sons4 ,this ,fascinating ,oil ,business4 ,by ,m4 ,w4 ,ball1 #aidj1 ,bobbs-,merrill ,co4 ,a simple and elementary description of the petroleum industry4 ,geology of ,coal4 ,by ,o4 ,stutzer and ,a4 ,c4 ,noe1 #aidj1 ,university of ,chicago ,press4 ,,general ,,geology ,down to ,earth4 ,by ,c4 ,croneis and ,w4 ,c4 ,krumbein1 #aicf1 ,university of ,chicago ,press4 ,an introduction to geology1 profusely illustrated4 ,textbook of ,geology ,part ,i--,physical ,geology4 #dth ,edition1 by ,c4 ,r4 ,longwell1 ,a4 ,knopf1 and ,r4 ,f4 ,flint1 #aici1 ,john ,wiley and ,sons4 ,a standard text on geology4 ,field ,geology4 #dth ,edition1 by ,f4 ,h4 ,lahee1 #aida1 ,mc,graw-,hill ,book ,co4 ,recognition and interpretation of geologic structures and topographic forms as they are observed1 and methods of geologic work4 ,,precious ,,stones ,a ,book of ,precious ,stones4 ,by ,j4 ,wodiska1 #aiaj1 ,g4 ,p4 ,putnam's ,sons4 ,written for jewelers1 but of general interest4 ,the ,curious ,lore of ,precious ,stones4 ,by ,g4 ,f4 ,kunz1 #aiac1 ,lippincott4 ,legends and stories of the gem minerals4 ,the ,magic of ,jewels and ,charms4 ,by ,g4 ,f4 ,kunz1 #aiae1 ,lippincott4 ,popular ,gemology4 ,by ,r4 ,m4 ,pearl1 #aidh1 ,john ,wiley and ,sons4 ,scientific and industrial uses of gems1 current information about their locality and production4 ,,fossils ,an ,introduction to the ,study of ,fossils4 ,by ,h4 ,w4 ,shimer1 #aicc1 ,macmillan ,co4 ,an introductory textbook about fossil plants and animals4 ,invertebrate ,paleontology4 ,by ,w4 ,h4 ,twenhofel and ,r4 ,p4 ,shrock1 #aice1 ,mc,graw-,hill ,book ,co4 ,textbook of ,geology ,part ,,ii--,historical ,geology4 #dth ,edition1 by ,c4 ,schuchert and ,c4 ,o4 ,dunbar1 #aida1 ,john ,wiley and ,sons4 ,the story of the development of life through the ages4 ,,index ,a ,actinolite1 #abj ,adobe1 #baj ,agate1 #ajg ,agate1 moss1 #gc1 #ajh ,alabaster1 #aeb ,albertite1 #bbi ,albite1 #aaj1 #aac1 #aae ,almandine1 #ig ,almandite1 #abb1 #abc ,aluminum bronze1 #gd ,aluminum group1 #gc ,amazon stone1 #aad ,amber1 #bbc ,amethyst1 #ajd ,amethyst1 ,oriental1 #ge ,amianthus1 #abj ,amphibole group1 #aai ,amygdoloid1 #aid ,amygdoloidal1 #agf ,analcite1 #ada ,andesite1 #aac1 #ahg ,andradite1 #abb1 #abd ,anglesite1 #fb ,anhydrite1 #adi ,anorthite1 #aaj1 #aac ,anorthosite1 #ahc ,anthracite1 #bah1 #bbb ,antimony1 #ha ,antimony1 gray1 #ha ,apatite1 #afj ,aquamarine1 #abe ,aragonite1 #adg ,argentite1 #ce ,argillite1 #bdb ,arkose1 #bjf ,arsenic group1 #gh ,arsenopyrite1 #gi ,asbestos1 #abj1 #adj ,augite1 #aah ,aventurine1 #ajd ,azurite1 #df ,b ,barite1 #aed ,barium group1 #aed ,basalt1 #ahh ,batholith1 #agd ,bauxite1 #gg ,beryl1 #abe ,beryl1 golden1 #abe ,beryllium1 #abe ,bibliography1 #bgj ,biotite1 #abi1 #acj ,bitumen1 #bbh ,black jack1 #fe ,bloodstone1 #ajf ,bog lime1 #bac ,bombs1 #aia ,boracite1 #afd ,borax1 #afe ,bornite1 #da ,brass1 #fd ,breccia1 #aia1 #aih ,brittania metal1 #ha ,bronze1 #ch ,bronze ,age1 #ch ,bronzite1 #aah ,bytownite1 #aac ,c ,calamine1 #fh ,calaverite1 #cj ,calcite1 #add ,calcium1 #adc ,carbon1 #aef ,carbonite1 #bbb ,carbuncle1 #abd ,carnelian1 #ajf ,carnotite1 #ij ,cassiterite1 #ic ,cat's eye1 #ajd ,celestite1 #aec ,cerargyrite1 #cg ,cerrusite1 #fa ,ceylonite1 #ig ,chalcedony1 #ajd1 #ajf ,chalcocite1 #db ,chalcopyrite1 #dj ,chalcotrichite1 #de ,chalk1 #bac ,chert1 #ajg ,chlorite1 #adj ,chlorospinel1 #ih ,chromite1 #hg ,chromium1 #hf ,chrysocola1 #dg ,chrysolite1 #acd1 #adj ,chrysoprase1 #ajf ,cinnabar1 #ia ,cinnamon stone1 #abc ,citrine1 #ajc ,clay1 #bjg ,clay1 ball1 #bjh ,clay1 brick1 #bji ,clay1 china1 #bjh ,clay1 fire1 #bjh ,clay1 paving brick1 #bji ,clay1 sewer-pipe1 #bji ,clay1 slip1 #bji ,clay1 stoneware1 #bji ,clay stones1 #bej ,cleavage1 #ba ,cleavage1 slaty1 #bcd ,coal1 #bag ,coal1 bituminous1 #bab1 #bbj ,coal1 cannel1 #bba ,coal1 hard1 #bbb ,coal1 soft1 #bbj ,cobalt1 #hd ,cobalt bloom1 #he ,cobalt glance1 #he ,cobalt gray ore1 #he ,cobaltite1 #hc ,coke1 #bbj ,colemanite1 #afe ,collecting1 #e1 #g ,color1 #bc ,concretions1 #bdh ,concretions1 flint1 #bec ,concretions1 lime1 #bea ,concretions1 other1 #bee ,concretions1 sandstone1 #bec ,conglomerate1 #bjb ,copper1 #cg1 #ci ,copper1 blushing1 #db ,copper1 glance1 #db ,copper1 grey1 #dc ,copper1 peacock1 #db ,copper1 plush1 #de ,copper1 purple1 #da ,copper1 red1 #dd ,copper1 variegated1 #db ,copper1 yellow1 #dj ,coquina1 #bac ,coral1 #adf ,coral rock1 #bad ,corundum1 #ge ,crude oil1 #bbg ,cryolite1 #gh ,crystal balls1 #aja ,crystal formation1 #ad ,crystal rock1 #ajc ,crystal structure1 #aa ,crystal systems1 #ac-ah ,cuprite1 #dd ,cyanite1 #abh ,d ,dacite1 #ahg ,dense1 #agf ,diamond1 #aeg ,diamonds1 ,matura1 #abg ,diamonds1 slave's1 #acc ,diatoms1 #bca ,dikes1 #agd ,diorite1 #ahb ,dog-tooth spar1 #ade ,dolomite1 #ii ,dry bone1 #fh ,e ,earth1 diatomaceous1 #bc ,elements1 listed1 #bfg ,emerald1 #abe ,emerald1 ,oriental1 #ge ,emery1 #gf ,enstatite1 #aag ,epidote1 #acd ,equipment1 #g ,erubescite1 #db ,extrusive1 #agc ,f ,feldspar1 #aaj ,feldspar1 alkalic1 #aaa ,felsite1 #ahf ,felsitic1 #agf ,ferromanganese1 #gj ,flagstone1 #bjg ,flint1 #ajf ,fluorine1 #afb ,fluorite1 #afb ,fossils1 #bff ,fragmental1 #agf ,franklinite1 #fi ,freestone1 #bjg ,g ,gabbro1 #ahc ,galena1 #fj ,garnet group1 #aba ,garnet1 ,sirian1 #abc ,geodes1 #bee ,german silver1 #hb ,gilsonite1 #bbi ,glassy1 #agf ,glucinum1 #abe ,gneiss1 #bcg ,goethite1 #ea1 #eb ,gold1 #ca ,gold foil1 #fd ,gold group1 #bi ,gossan1 #ej ,granite1 #agh ,granite1 graphic1 #agi ,granitoid1 #agf ,graphite1 #aef1 #bai ,gravel1 #bja ,graywacke1 #bjf ,grit1 #bjf ,grossularite1 #abb1 #abc ,guano1 #bcj ,gumbo1 #baj ,gypsum1 #aej ,h ,halite1 #afc ,hardness1 #bj ,hardpan1 #baf ,heavy spar1 #aed ,heliotrope1 #ajf ,hematite1 #ec ,hemihedral forms1 #ai ,hercynite1 #ih ,hexagonal system1 #ah ,hornblende1 #aba ,hornstone1 #ajg ,hyacinth1 #abg ,hypersthene1 #aah ,i ,ice1 #afg ,iceland spar1 #ade ,ice stone1 #gh ,ilmenite1 #id ,intrusive1 #agd ,iron1 #dg ,iron1 bog1 #ej ,iron1 chromic1 #hg ,iron1 magnetic1 #ed ,iron pyrites1 #ef ,iron1 spathic1 #ee ,iron1 specular1 #ec ,isometric system1 #ac ,j ,jacinth1 #abg ,jargons1 #abg ,jargoons1 #abg ,jasper1 #ajf ,jet1 #bbb ,k ,kaolin1 #acg1 #bjh ,kaolinite1 #acg ,l ,labels1 #e ,labradorite1 #aac1 #aaf ,laccolith1 #agd ,lapilli1 #aia ,lava1 #agc ,lead1 #ei ,lead glance1 #fj ,lead1 green ore1 #fc ,lead1 white ore1 #fa ,lepidolite1 #abi1 #acj ,lignite1 #bah1 #bai ,limestone1 #bab ,limestone1 encrinal1 #bad ,limestone1 hydraulic1 #bad ,limestone1 lithographic1 #bad ,limonite1 #di1 #ea ,loess1 #baj ,luster1 #bc ,m ,magma1 #agc ,magnesite1 #ih ,magnesium group1 #if ,magnetite1 #ed ,malachite1 #de ,malanite1 #abd ,malta1 #bbi ,manganese group1 #gj ,manganite1 #gb ,marble1 #bdc ,marble1 ,suisun1 #adf ,marcasite1 #eg ,marl1 #baa ,mercury1 #ij ,meteorites1 #bfb ,mica group1 #abh ,microcline1 #aac1 #aad ,millerite1 #hc ,mineral tables1 #be ,minerals1 defined1 #aj ,molybdenite1 #ha ,molybdenum1 #hj ,monoclinic system1 #ag ,monzonite1 #aha ,morion1 #ajc ,mother-of-pearl1 #adh ,muscovite1 #abi ,n ,natrolite1 #adb ,natural gas1 #bbg ,needle iron stone1 #eb ,niccolite1 #hc ,nickel1 copper1 #hc ,nickel group1 #hb ,o ,obsidian1 #aia ,ochre red1 #ed ,ochre yellow1 #di ,oligoclase1 #aac1 #aae ,olivine1 #acd ,olivine-gabbro1 #ahc ,onyx1 #ajh ,onyx1 ,californian1 #adf ,onyx marble1 #bae ,onyx1 ,mexican1 #adf ,oolites1 #bed ,opal1 #ajh ,opal-agate1 #aji ,opal1 common1 #aji ,opal1 fire1 #aji ,opal1 precious1 #aji ,ophicalcite1 #bdf ,ophiolite1 #bdf ,orpiment1 #hj ,orthoclase1 #aaj1 #aac ,orthorhombic system1 #af ,p ,paste1 #ajc ,pearls1 #adh ,pearlstone1 #aic ,peat1 #bah1 #bai ,pebbles1 #bef ,pegmatite1 #agi ,peridot1 #acd ,peridotite1 #ahd ,perlite1 #aic ,petroleum series1 #bbd1 #bbg ,pewter1 #fj ,phenocrysts1 #ahi ,phlogopite1 #abi1 #aca ,phosphate1 #afj1 #bcj ,phosphorus1 #aei ,phyllite1 #bdb ,picotite1 #ig ,pisolite1 #bee ,pitchstone1 #aic ,plagioclase1 #aaa ,plasma1 #ajf ,platinum1 #ie ,plumbago1 #aef ,porous1 #agf ,porphyritic1 #agf ,porphyry1 #ahi ,prase1 #ajd ,prousite1 #cf ,psilomelane1 #gb ,pumice1 #aic ,pyrargyrite1 #ce ,pyrite1 #ef ,pyrite1 capillary1 #hc ,pyrite1 magnetic1 #eh ,pyrite1 white1 #eg ,pyritohedron1 #ef1 #cah ,pyrolusite1 #ga ,pyromorphite1 #fc ,pyrope1 #abb1 #abc ,pyroxene group1 #aaf ,pyroxenite1 #ahe ,pyrrhotite1 #eh ,q ,quartz1 #ajj ,quartz-diorite1 #aha ,quartz1 milky1 #ajc ,quartz1 rose1 #ajd ,quartz1 smoky1 #ajc ,quartzite1 #bci ,quicksands1 #bjd ,quicksilver1 #ij ,r ,radium1 #hi ,realgar1 #hj ,rhinestones1 #aja ,rhodochrosite1 #gc ,rhyolite #ahe ,rock1 phosphate1 #bcj ,rocks1 #agj ,rocks1 defined1 #aj ,rocks1 igneous1 #agb ,rocks1 igneous1 classified1 #agg ,rocks1 metamorphic1 #bcb ,rocks1 metamorphic1 classified1 #bcf ,rocks1 sedimentary1 #aid ,rocks1 sedimentary1 classified1 #aif ,rubicelle1 #ig ,ruby1 #ge ,ruby1 ,balas1 #ig ,ruby mica1 #eb ,rutile1 #id ,s ,salt1 #afc ,sand1 #bjb ,sandstone1 #bje ,sapphire1 #ge ,sapphire1 ,oriental white1 #ge ,sardonyx1 #ajh ,satin spar1 #adf ,schist1 #bdj ,schistosity1 #bcd ,scoria1 #aib1 #aic ,septeria1 #beb ,sericite1 #acj ,serpentine1 #aci1 #bde ,shale1 #baj ,shale1 oil-bearing1 #bbe ,sheet1 #agc ,siderite1 #ee ,silica1 #ii ,silicates1 #ii ,silicon1 #ii ,sill1 #agd ,sillimanite1 #abh ,silver1 #cd ,silver1 dark red1 #ce ,silver1 ,german1 #fe ,silver glance1 #ce ,silver group1 #cb ,silver1 horn1 #cg ,silver1 light red1 #cf ,silver1 ruby1 #ce ,sinter1 #aaj ,slate1 #bda ,smalt1 #hd ,smaltite1 #he ,smithsonite1 #fh ,soapstone1 #bdd ,sodalite1 #abf ,soil1 #aih ,solder1 #fj ,specific gravity1 #bb ,speigeleisen1 #gj ,spelter1 #fd ,spessartite1 #abb1 #abc ,sphalerite1 #fe ,spinel1 #ig ,spinel-ruby1 #ig ,stalactites1 #adf ,stalagmites1 #adf ,staurolite1 #acc ,steatite1 #bdd ,stellite1 #hd1 #hh ,stibnite1 #ha ,stilbite1 #adc ,stock1 #agd ,streak1 #bc ,strontianite1 #aeb ,strontium group1 #aeb ,sulphur1 #aff ,syenite1 #ahj ,sylvanite1 #cj ,t ,talc1 #ach ,talus1 #aig ,tetragonal system1 #ae ,tetrahedrite1 #dc ,tile ore1 #de ,till1 #bae ,tillite1 #bag ,time chart1 #bfh ,tin1 #ib ,tin stone1 #ic ,titanium1 #ic ,tonalite1 #aha ,topaz1 #aca ,topaz1 false1 #ajc ,topaz1 ,oriental1 #ge ,topaz1 ,saxon1 #acb ,topaz1 ,scotch1 #acb ,topaz1 smoky1 #acb ,topaz1 ,spanish1 #acb ,tourmaline1 #ace ,trachite1 #ahf ,trap1 #ahh ,travertine1 #adf1 #bae ,tremolite1 #abj ,triclinic system1 #ah ,tripolite1 #aaj ,tufa1 calcareous1 #adg ,tuff1 #aij ,tungsten1 #hg ,turgite1 #ea ,turquois1 #afa ,twinning1 #ai ,type metal1 #fj ,u ,uintaite1 #bbi ,uranium1 #hi ,uvarovite1 #abb1 #abc ,v ,vanadium1 #hi ,verde antique1 #bdg ,volcanic ash1 #aij ,volcanic blocks1 #aia ,w ,water1 #afg ,white metal1 #fd ,willemite1 #fg ,witherite1 #aec ,wolframite1 #hh ,wood1 agatized1 #ajh ,wood1 opalized1 #aji ,wood1 silicified1 #ajh ,x ,xanthosiderite1 #ea ,z ,zeolites1 #ada ,zinc1 #fc ,zinc blende1 #fe ,zinc red ore1 #ff ,zinc1 ruby1 #fe ,zincite1 #ff ,zircon1 #abg ,plate ,frontispiece ,illustration3 ,tourmaline crystals1 growing amid feldspar crystals in a cavity in granite1 from ,paris1 ,me4 ,plate #e ,illustration3 ,gold in quartz1 from ,california ,plate #f ,illustration3 ,native silver in calcite ,illustration3 ,argentite1 the black masses throughout the white quartz ,plate #g ,illustration3 ,pyrargyrite as it appears after moderate exposure to the light4 ,illustration3 ,crystal form of ,pyrargyrite ,illustration3 ,prousite as it appears after moderate exposure to the light ,plate #h ,illustration3 ,native copper from ,michigan ,illustration3 ,chalcopyrite in tetrahedrons and an occasional octahedron4 ,plate #i ,illustration3 ,chalcocite crystals with the bluish tarnish ,illustration3 ,tetrahedrite crystals ,plate #aa ,illustration3 ,cuprite1 the red crystals showing characteristic color1 other showing the green tarnish of malachite ,illustration3 ,malachite 7green7 and azurite 7blue71 the two minerals shown together as they very commonly occur ,plate #ab ,illustration3 ,limonite ,illustration3 ,the crystal form in which goethite is found1 p is the prism faces1 b and c are faces formed by beveling the edges of the prism1 o is the pyramidal face characteristic of the ends ,plate #ac ,illustration3 ,hematite1 ,clinton iron ore1 oolitic ,illustration3 ,siderite crystals ,plate #ae ,illustration3 ,pyrite crystals ,illustration3 ,marcasite in concretionary form with radiate structure ,plate #ag ,illustration3 ,galena in crystals ,illustration3 ,pyromorphite crystals 7green7 ,plate #ai ,illustration3 ,sphalerite1 some the normal yellow and some crystals with the reddish tinge4 7,white is dolomite7 ,illustration3 ,zincite ,plate #ba ,illustration3 ,smithsonite in yellow crystals ,illustration3 ,franklinite in octahedral crystals ,plate #bd ,illustration3 ,arsenopyrite1 showing crystals massed so as to be incompletely developed ,illustration3 ,realgar as it usually occurs in powdery incrustations ,plate #be ,illustration3 ,large crystal of stibnite1 the light colored face is the one parallel to which cleavage occurs ,illustration3 ,niccolite as a vein in slate ,plate #bf ,illustration3 ,cobaltite1 silver color1 with pink tinge ,illustration3 ,smaltite1 pink is cobalt bloom ,plate #bg ,illustration3 ,carnotite from southwest ,colorado ,illustration3 ,cinnabar ,plate #ca ,illustration3 ,amethyst1 not however deep enough colored for gems ,illustration3 ,jasper1 with botryoidal surface ,plate #cb ,illustration3 ,banded ,agate from ,brazil ,plate #cc ,illustration3 ,common ,opal from ,arizona ,illustration3 ,siliceous sinter or ,geyserite from ,the ,yellowstone ,park ,plate #ce ,illustration3 ,a group of ,microcline crystals from ,pike's ,peak1 ,colo4 ,illustration3 ,labradorite1 showing multiple twinning 7the striation71 and the iridescent play of colors ,plate #cf ,illustration3 ,crystal form of a pyroxene2 a and b prism faces1 m the beveled edge between two prism faces ,illustration3 ,cross section of a pyroxene crystal showing the lines of intersection of the two cleavage planes ,illustration3 ,cross sections of pyroxenes1 showing typical forms taken by crystals ,illustration3 ,augite crystals1 in crystalline limestone ,plate #ch ,illustration3 ,the dodecahedron and the #bd-sided figure characteristic of garnets ,illustration3 ,the garnet1 grossularite ,illustration3 ,the garnet alamandite ,plate #ci ,illustration3 ,beryl of gem quality ,illustration3 ,zircon in syenite ,plate #dj ,illustration3 ,cyanite crystals in schist ,illustration3 ,a crystal of mica1 showing basal cleavage ,plate #da ,illustration3 ,crystal form typical of topaz ,illustration3 ,a topaz crystal from ,brazil ,illustration3 ,crystal form typical of staurolite when simple ,illustration3 ,a typical twin of staurolite ,plate #dc ,illustration3 ,serpentine ,illustration3 ,chlorite ,plate #di ,illustration3 ,apatite crystals in crystalline calcite ,illustration3 ,the ends of apatite crystals showing common modes of termination ,plate #ej ,illustration3 ,a group of fluorite crystals ,illustration3 ,a group of halite crystals ,plate #fa ,illustration3 ,amber ,illustration3 ,two bottles of petroleum1 the left hand one with a paraffin base1 the right hand one with an asphalt base ,plate #fe ,illustration3 ,mica schist1 with garnets ,illustration3 ,chlorite schist ,plate #fg ,illustration3 ,serpentine1 composed of serpentine1 hematite1 and some calcite ,plate #a ,basal forms of the isometric system ,illustration3 ,cube ,illustration3 ,octahedron ,illustration3 ,dodecahedron ,plate #b ,basal forms of the tetragonal system ,illustration3 ,a square prism ,illustration3 ,octahedron ,basal forms of the orthorhombic system ,illustration3 ,a ,rectangular prism ,illustration3 ,octahedron ,plate #c ,basal forms of the monoclinic system ,illustration3 ,the rectangular prism askew ,illustration3 ,the octahedron ,illustration3 ,a cross section of the prism with its edges beveled so that the b faces are obliterated by the m faces1 and a six-sided prism is formed 7pseudo-hexagonal7 ,illustration3 ,basal form of the triclinic system ,plate #d ,basal forms of the hexagonal system ,illustration3 ,the six-sided prism ,illustration3 ,the double pyramid ,illustration3 ,the rhombohedron ,plate #aj ,illustration3 ,tetrahedrons showing characteristic manner in which tetrahedrite occurs ,illustration3 ,a cube with the edges beveled and the corners cut in a form characteristic of cuprite ,plate #cj ,illustration3 ,two intergrowing or twinned quartz crystals ,illustration3 ,diagram of the typical quartz crystal1 p prism faces1 l left hand rhombohedron1 r right hand rhombohedron ,illustration3 ,a quartz crystal on which the left hand rhombohedron is represented by small faces while the right hand rhombohedron has large faces ,plate #ad ,illustration3 ,crystal forms of hematite1 ,a the rhombohedron with the edges beveled2 ,b the tabular form1 resulting from the excessive development of the two o faces opposite each other ,illustration3 ,a typical crystal of magnetite ,illustration3 ,the rhombohedron typical of siderite ,plate #af ,illustration3 ,the pyritohedron ,illustration3 ,the pyritohedron with certain of its edges beveled by the cube faces1 to show the relationship of these two forms ,plate #ah ,typical forms for cerrusite ,illustration3 ,the pyramid1 n the prism face1 m the beveled prism1 p the octahedral face1 and o the edge of the octahedral faces beveled ,illustration3 ,the simple type of twinning ,illustration3 ,a multiple twin where three crystals grow through each other ,illustration3 ,forms in which anglesite occurs3 l the pyramid face1 p the prism face1 o the vertical edge of the prism beveled1 m the horizontal edge of the prism beveled1 n a further beveling of the horizontal edge of the prism4 ,d the tabular1 ,e the prismatic form ,plate #bj ,illustration3 ,a characteristic form in which sphalerite may occur2 being the combination of1 d the dodecahedron1 o the octahedron1 and t1 a #bd-sided figure ,illustration3 ,characteristic form for zincite crystals1 n the hexagonal prism1 and p pyramidal faces on it ,illustration3 ,typical form of crystal of willemite3 p the prism1 r rhombohedron faces on end1 r a second lower rhombohedron ,plate #bb ,illustration3 ,moss agates1 showing the dendritic growth of manganitic minerals1 like manganite or pyrolusite ,illustration3 ,moss agates ,illustration3 ,crystal form of manganite ,plate #bc ,illustration3 ,crystals of green corundum in syenite1 from ,montana ,illustration3 ,typical crystal forms of corundum3 ,a the elongated prism with the alternate corners cut by rhombohedral faces1 ,b the tabular prism1 ,c the double pyramid ,plate #bh ,illustration3 ,cassiterite1 twinned crystals ,illustration3 ,the crystal form in which both cassiterite and rutile occur when in simple crystals1 p prism faces1 m beveling of the prism1 o octahedral face1 n beveling of the edge between octahedral faces ,illustration3 ,multiple twinning characteristic of rutile ,plate #bi ,illustration3 ,crystal of ,spinel ,crystal forms in which dolomite occurs ,illustration3 ,a the cleavage form1 rhombohedron with the faces curved ,illustration3 ,b the rhombohedron with the corners cut1 as it often occurs ,illustration3 ,c the form found in gypsum or anhydrite ,plate #cd ,illustration3 ,orthoclase1 a cleavage piece1 a and b the perfect cleavage planes1 and c the imperfect cleavage plane ,crystal forms of orthoclase ,illustration3 ,a the simple crystal ,illustration3 ,b the twinned form ,illustration3 ,c the twinned form in which the crystals are intergrowing ,illustration3 ,diagram of a multiple twin of a plagioclase feldspar ,plate #cg ,diagrams of amphibole crystals ,illustration3 ,a a typical crystal ,illustration3 ,b cross section showing the intersection of cleavage planes ,illustration3 ,c and ,d cross sections to show variations in outline ,illustration3 ,tremolite in silky fibrous crystals4 ,asbestos ,illustration3 ,hornblende crystals in quartzite ,plate #db ,illustration3 ,epidote crystals ,illustration3 ,typical forms of epidote crystals2 p prism faces1 m1 n1 x1 and y beveled edges of the prism1 o octahedral faces ,typical forms of tourmaline ,illustration3 ,a side view2 ,b and ,c ends to show terminations2 p prism faces1 m beveling of prism edges1 r a low rhombohedron on the end1 s the opposite rhombohedron1 b basal face1 and the other faces represent bevelings ,plate #dh ,illustration3 ,a group of barite crystals ,illustration3 ,outline of the typical tabular barite crystal ,illustration3 ,the six-sided double pyramid1 composed of three interpenetrating crystals1 typical of witherite and strontianite ,plate #dd ,illustration3 ,the typical form of analcite ,illustration3 ,a typical natrolite crystal ,illustration3 ,the typical crystal form of stilbite ,illustration3 ,a sheaf-like bundle of fibrous crystals1 typical of stilbite ,plate #de ,illustration3 ,a group of calcite crystals ,typical forms of calcite ,illustration3 ,a the rhombohedron formed by cleavage ,illustration3 ,b a rhombohedral crystal truncated by the basal plane ,illustration3 ,c the scalenohedron ,illustration3 ,d the scalenohedron truncated by the rhombohedron ,illustration3 ,e the scalenohedron on a prism ,plate #df ,typical forms of aragonite ,illustration3 ,a the simple crystal ,illustration3 ,b a needle-like form1 twinned ,illustration3 ,c cross section to show how the form may appear six-sided ,illustration3 ,typical form of the anhydrite crystal ,plate #dg ,illustration3 ,a piece of gypsum looking on the surface of the perfect cleavage1 and showing the two other cleavages as lines1 intersecting at #ff4 ,twinning is also shown ,illustration3 ,a simple crystal of gypsum ,illustration3 ,twin crystals of gypsum ,plate #ea ,illustration3 ,sulphur crystals ,illustration3 ,ice crystals1 the top one1 the end of a hexagonal prism2 the two lower figures multiple twins as in snow flakes ,plate #eb ,illustration3 ,the ,devil's ,tower1 ,wyoming1 an example of igneous rock with columnar structure1 and resting on sedimentary rocks4 ,courtesy of the ,u4 ,s4 ,geological ,survey ,plate #ec ,illustration3 ,a coarse granite ,illustration3 ,graphic granite ,plate #ed ,illustration3 ,syenite ,illustration3 ,gabbro ,plate #ee ,illustration3 ,basalt-porphyry4 ,the large white crystals are phenocrysts of plagioclase feldspar ,illustration3 ,basalt-obsidian ,plate #ef ,illustration3 ,amgydoloid ,plate #eg ,illustration3 ,the north face of ,scott's ,bluff1 ,neb41 showing sedimentary sandstones above and clays below4 ,the type of erosion is characteristic of arid regions4 ,courtesy of the ,u4 ,s4 ,geological ,survey ,plate #eh ,illustration3 ,breccia ,illustration3 ,conglomerate ,plate #ei ,illustration3 ,calcareous shale ,illustration3 ,coquina ,plate #fj ,illustration3 ,foramenifera from ,chalk2 enlarged about #be diameters ,illustration3 ,encrinal ,limestone2 fragments of the stems1 arms and body of ,crinoids ,plate #fb ,illustration3 ,a diatomaceous earth magnified #ej times ,illustration3 ,b and ,c two diatoms from the above enlarged #bej times4 ,after ,gravelle1 by the courtesy of ,natural ,history ,plate #fc ,illustration3 ,a metamorphic rock1 showing the contortion of layers due to expansion under heat ,plate #fd ,illustration3 ,a conglomerate partly metamorphosed to a gneiss4 ,note the flattened pebbles and the alternation of the intermediate material to mica scales1 etc4 ,illustration3 ,a typical gneiss ,plate #ff ,illustration3 ,phyllite ,illustration3 ,a white marble1 with black streaks due to graphite ,plate #fh ,illustration3 ,claystones1 simple and compound ,illustration3 ,a line concretion1 which on splitting disclosed a fern leaf of the age of the coal measures ,plate #fi ,illustration3 ,a septeria from ,seneca ,lake1 ,n4 ,y4 ,illustration3 ,pisolite ,plate #gj ,illustration3 ,a geode filled with quartz crystals ,plate #ga ,illustration3 ,a quartz pebble from the bed of a ,new ,england brook ,illustration3 ,a pebble of schist and granite from the foot of ,mt4 ,toby1 ,mass4 ,plate #gb ,illustration3 ,an iron-nickel meteorite1 of #bc lbs4 which fell in ,claiborne ,co41 ,tenn4 ,illustration3 ,an etched slice of an iron meteorite which fell in ,reed ,city1 ,osceola ,co41 ,mich4 ,plate #gc ,illustration3 ,a stony meteorite1 about natural size1 which fell in #ahge1 in ,iowa ,co41 ,iowa ,,putnam',s ,,nature ,,field ,,books ,companion books to this one ,mathews ,american ,wild ,flowers ,american ,trees and ,shrubs ,wild ,birds and ,their ,music ,durand ,wild ,flowers in ,homes and ,gardens ,my ,wild ,flower ,garden ,common ,ferns ,lutz ,insects ,loomis ,rocks and ,minerals ,eliot ,birds of the ,pacific ,coast ,armstrong ,western ,wild ,flowers ,alexander ,birds of the ,ocean ,anthony ,north ,american ,mammals ,thomas ,common ,mushrooms ,sturgis ,birds of the ,panama ,canal ,zone ,miner ,seashore ,life ,breder ,marine ,fishes of the ,atlantic ,coast ,morgan ,ponds and ,streams ,longyear ,rocky ,mountain ,trees and ,shrubs ,olcott ,field ,book of the ,skies ,putnam ,beebe ,the ,shore ,fishes of ,bermuda ,tee-,van ,schrenkeisen ,fresh-,water ,fishes of ,north ,america ,north of ,mexico ,transcriber's ,notes --,retained publication information from the printed edition3 this e,book is public-domain in the country of publication4 --,in the text versions only1 text in italics is delimited by underscores4 --,silently corrected a few typos4 --,reconstructed an image caption 7,pisolite7 on ,plate #fi4 --,generated a cover image based on elements in the book4