file which includes the original illustrations4 ,see #bhjeh-;h4htm or #bhjeh-;h4zip3 7https3_/_/www4gutenberg4org_/dirs_/#b_/ h_/j_/e_/bhjeh_/bhjeh-;h_/#bhjeh-;h4htm7 or 7https3_/_/www4gutenberg4org_/dirs_/#b_/ h_/j_/e_/bhjeh_/bhjeh-;h4zip7 ,by ,frank ,b4 ,wade ,diamonds ,a ,text-,book of ,precious ,stones ,a ,,text-,,book ,,of ,,precious ,,stones ,,for ,,jewelers ,,and ,,the ,,gem-,,loving ,,public by ,,frank ,b4 ,,wade1 ,b4,s4 ,head of the ,department of ,chemistry1 ,shortridge ,high ,school1 ,indianapolis1 ,ind4 ,author of ,diamonds3 ,a ,study of the ,factors ,that ,govern ,their ,value ,illustrated ,g4 ,p4 ,putnam's ,sons ,new ,york and ,london ,the ,knickerbocker ,press ,copyright1 #aiah by ,frank ,b4 ,wade ,first printing1 ,january1 #aiah ,second ,march1 #aibd ,device ,made in the ,united ,states of ,america ,,preface ,in this little text-book the author has tried to combine the trade information which he has gained in his avocation1 the study of precious stones1 with the scientific knowledge bearing thereon1 which his vocation1 the teaching of chemistry1 has compelled him to master4 ,in planning and in writing the book1 every effort has been made to teach the fundamental principles and methods in use for identifying precious stones1 in as natural an order as possible4 ,this has been done in the belief that the necessary information will thus be much more readily acquired by the busy gem merchant or jeweler than would have been the case had the material been arranged in the usual systematic order4 ,the latter is of advantage for quick reference after the fundamentals of the subject have been mastered4 ,it is hoped1 however1 that the method of presentation used in this book will make easy the acquisition of a knowledge of gemology and that many who have been deterred from studying the subject by a feeling that the difficulties due to their lack of scientific training were insurmountable1 will find that they can learn all the science that is really necessary1 as they proceed4 ,to that end the discussions have been given in as untechnical language as possible and homely illustrations have in many cases been provided4 ,nearly every portion of the subject that a gem merchant needs to know has been considered and there is provided for the interested public much material which will enable them to be more intelligent purchasers of gem-set jewelry1 as well as more appreciative lovers of ,nature's wonderful mineral masterpieces4 ,f4 ,b4 ,w4 ,,indianapolis1 ,december #bf1 #aiaf ,,introduction ,because of the rapid increase in knowledge about precious stones on the part of the buying public1 it has become necessary for the gem merchant and his clerks and salesmen to know at least as much about the subject of gemology as their better informed customers are likely to know4 ,in many recent articles in trade papers1 attention has been called to this need1 and to the provision which ,columbia ,university has made for a course in the study of gems4 ,the action of the ,national ,association of ,goldsmiths of ,great ,britain in providing annual examinations in gemology1 and in granting certificates and diplomas to those who successfully pass the examinations1 has also been reported1 and it has been suggested that some such course should be pursued by jewelers' associations in this country4 ,the greatest difficulty in the way of such formal study among our jewelers and gem merchants is the lack of time for attendance on formal courses1 which must necessarily be given at definite times and in definite places4 ,as a diamond salesman was heard to say recently3 ,the boss said he wanted me to take in that course at ,columbia1 but he didn't tell me how ,i was going to do it4 ,here ,i am a thousand miles from ,columbia1 and it was only six weeks ago that he was telling me ,i ought to take that course4 ,i can't stay around ,new ,york all the time4 ,similarly those whose work keeps them in ,new ,york might object that their hours of employment prevented attendance on day courses1 and that distance from the university and fatigue prevent attendance on night courses4 ,the great mass of gem dealers in other cities must also be considered4 ,it will therefore be the endeavor of this book to provide guidance for those who really want to make themselves more efficient in the gem business1 but who have felt that they needed something in the way of suggestion regarding what to attempt1 and how to go about it4 ,study of the sort that will be suggested can be pursued in spare moments1 on street cars or elevated trains1 in waiting rooms1 or in one's room at night4 ,it will astonish many to find how much can be accomplished by consistently utilizing spare moments4 ,booker ,t4 ,washington is said to have written in such spare time practically all that he has published4 ,for the practical study of the gems themselves1 which is an absolutely essential part of the work1 those actually engaged in the trade have better opportunities than any school could give and1 except during rush seasons1 there is plenty of time during business hours for such study4 ,no intelligent employer will begrudge such use of time for which he is paying1 if the thing be done in reason and with a serious view to improvement4 ,the frequent application of what is acquired1 as opportunity offers1 in connection with ordinary salesmanship1 will help fix the subject and at the same time increase sales4 ,many gem dealers have been deterred from beginning a study of gems because of the seeming difficulties in connection with the scientific determination of the different varieties of stones4 ,now science is nothing but boiled-down common sense1 and a bold front will soon convince one that most of the difficulties are more apparent than real4 ,such minor difficulties as exist will be approached in such a manner that a little effort will overcome them4 ,for those who are willing to do more work1 this book will suggest definite portions of particular books1 which are easily available1 for reference reading and study--but the lessons themselves will attempt to teach the essential things in as simple a manner as is possible4 ,perhaps the first essential for the gem merchant is to be able surely to distinguish the various stones from one another and from synthetic and imitation stones4 ,that such ability is much needed will be clear to anyone who in casting a backward glance over his experience recalls the many serious mistakes that have come to his knowledge4 ,many more have doubtless occurred without detection4 ,several times recently the author has come across cases where large dealers have been mistaken in their determination of colored stones1 particularly emeralds4 ,only the other day a ring was brought to me that had been bought for a genuine emerald ring after the buyer had taken it to one of the dealers in his city and had paid for an examination of it1 which had resulted in its being declared genuine4 ,on examining the stone with a lens of only moderate power1 several round air bubbles were noted in it1 and on barely touching it with a file it was easily scratched4 ,the material was green glass4 ,now1 what was said about the dealer who sold it and the one who appraised it may be imagined4 ,the long chain of adverse influence which will be put in action against those dealers1 even though the one who sold the stone makes good the loss1 is something that can be ill afforded by any dealer1 and all this might have been avoided by even a rudimentary knowledge of the means of distinguishing precious stones4 ,the dealer was doubtless honest1 but1 through carelessness or ignorance1 was himself deceived4 ,our first few lessons will therefore be concerned chiefly with learning the best means of telling the different stones from one another4 ,,contents ,,page ,,preface iii ,,lesson ,i4--,,how ,,stones ,,are ,,distinguished ,,from ,,one ,,another #a ,,ii4--,,refraction #d ,,iii4--,,double ,,refraction #h ,,iv4--,,absorption ,,and ,,dichroism #ae ,v4--,,specific ,,gravity #bc ,,vi4--,,specific ,,gravity ,,determinations #ca ,,vii4--,,luster ,,and ,,other ,,reflection ,,effects #ch ,,viii4--,,hardness #dg ,,ix4--,,hardness 7,continued7 #ee ,x4--,,dispersion #fj ,,xi4--,,color #ff ,,xii4--,,color 7,continued7 #ge ,,xiii4--,,color 7,continued7 #hg ,,xiv4--,,color 7,concluded7 #ic ,,xv4--,,how ,,to ,,tell ,,scientific ,,stones ,,from ,,natural ,,gems #ii ,,xvi4--,,how ,,to ,,test ,,an ,,unknown ,,gem #aji ,,xvii4--,,suitability ,,of ,,stones ,,for ,,various ,,types ,,of ,,jewels1 ,,as ,,determined ,,by ,,hardness1 ,,brittleness1 ,,and ,,cleavability #aai ,,xviii4--,,mineral ,,species ,,to ,,which ,,the ,,various ,,gems ,,belong ,,and ,,the ,,chemical ,,composition ,,thereof #acc ,,xix4--,,the ,,naming ,,of ,,precious ,,stones #adi ,,xx4--,,the ,,naming ,,of ,,precious ,,stones 7,concluded7 #afd ,,xxi4--,,where ,,precious ,,stones ,,are ,,found #agi ,,xxii4--,,how ,,rough ,,precious ,,stones ,,are ,,cut #bja ,,xxiii4--,,how ,,rough ,,precious ,,stones ,,are ,,cut ,,and ,,what ,,constitutes ,,good ,,make 7,concluded7 #bac ,,xxiv4--,,forms ,,given ,,to ,,precious ,,stones #bbg ,,xxv4--,,imitations ,,of ,,precious ,,stones #bcg ,,xxvi4--,,alteration ,,of ,,the ,,color ,,of ,,precious ,,stones #bej ,,xxvii4--,,pearls #beh ,,xxviii4--,,cultured ,,pearls ,,and ,,imitations ,,of ,,pearls #bgg ,,xxix4--,,the ,,use ,,of ,,balances ,,and ,,the ,,unit ,,of ,,weight ,,in ,,use ,,for ,,precious ,,stones #bhc ,,xxx4--,,tariff ,,laws ,,on ,,precious ,,and ,,imitation ,,stones #bid ,,bibliography #cja ,,index #cac ,a ,text-,book of ,precious ,stones ,,lesson ,i ,,how ,,stones ,,are ,,distinguished ,,from ,,one ,,another ,,precious ,,stones ,,distinguished ,,by ,,their ,,properties4 ,one precious stone is best distinguished from another just as substances of other types are distinguished1 that is to say1 by their properties4 ,for example1 salt and sugar are both white1 both are soluble in water1 and both are odorless4 ,so far the italicized properties would not serve to distinguish the two substances4 ,but sugar is sweet while salt is salty in taste4 ,here we have a distinguishing property4 ,now1 just as salt and sugar have properties1 so have all precious stones1 and while1 as was the case with salt and sugar1 many precious stones have properties in common1 yet each has also some properties which are distinctive1 and which can be relied upon as differentiating the particular stone from other stones4 ,in selecting properties for use in distinguishing precious stones1 such properties as can be determined by quantity1 and set down in numbers1 are probably more trustworthy than those that can be observed by mere inspection4 ,those also which have to do with the behavior of light in passing through the stone are extremely valuable4 ,,importance ,,of ,,numerical ,,properties4 ,it is because gem dealers so often rely upon the more obvious sort of property1 such as color1 that they so frequently make mistakes4 ,there may be several different types of stones of a given color1 but each will be found to have its own numerical properties such as density1 hardness1 refractive power1 dispersive power1 etc41 and it is only by an accurate determination of two or three of these that one can be sure what stone he has in hand4 ,it must next be our task to find exactly what is meant by each of these numerical properties1 and how one may determine each with ease and exactness4 ,,lesson ,,ii ,,refraction ,,explanation ,,of ,,refraction4 ,perhaps the surest single method of distinguishing precious stones is to find out the refractive index of the material4 ,to one not acquainted with the science of physics this calls for some explanation4 ,the term refraction is used to describe the bending which light undergoes when it passes 7at any angle but a right angle7 from one transparent medium to another4 ,for example1 when light passes from air into water1 its path is bent at the surface of the water and it takes a new direction within the water4 7,see ,fig4 #a47 ,illustration3 ,,fig4 #a4 ,,ab represents the path of light in the air and ,,bc its path in the water4 ,while every gem stone refracts light which enters it from the air1 each stone has its own definite ability to do this1 and each differs from every other in the amount of bending which it can bring about under given conditions4 ,the accurate determination of the amount of bending in a given case requires very finely constructed optical instruments and also a knowledge of how to apply a certain amount of mathematics4 ,however1 all this part of the work has already been done by competent scientists1 and tables have been prepared by them1 in which the values for each material are put down4 ,,the ,,herbert-,,smith ,,refractometer4 ,there is on the market an instrument called the ,herbert-,smith refractometer1 by means of which anyone with a little practice can read at once on the scale within the instrument the refractive index1 as it is called1 of any precious stone that is not too highly refractive4 7,its upper limit is #a4hj4 ,this would exclude very few stones of importance1 i4 e41 zircon1 diamond1 sphene1 and demantoid garnet47 ,those readers who wish to make a more intensive study of the construction and use of the refractometer will find a very full and complete account of the subject in ,gem-,stones and their ,distinctive ,characters1 by ,g4 ,f4 ,herbert-,smith1 ,new ,york2 ,james ,pott ,co41 #aiab4 ,chapter ,,iv41 pp4 #ba-cf4 ,the ,herbert-,smith refractometer is there described fully1 its principle is explained and directions for using it are given4 ,the price of the refractometer is necessarily so high 7duty included7 that its purchase might not be justified in the case of the smaller retailer4 ,every large dealer in colored stones1 whether importer1 wholesaler1 or retailer1 should have one1 as by its use very rapid and very accurate determinations of stones may be made1 and its use is not confined to unmounted stones1 for any stone whose table facet can be applied to the surface of the lens in the instrument can be determined4 ,,lesson ,,iii ,,double ,,refraction ,,explanation ,,of ,,double ,,refraction4 ,in ,lesson ,,ii4 we learned what is meant by refraction of light4 ,while glass and a small number of precious stones 7diamond1 garnet1 and spinel7 bend light as was illustrated in ,fig4 #a1 practically all the other stones cause a beam of light on entering them to separate1 and the path of the light in the stone becomes double1 as shown in ,fig4 #b4 ,this behavior is called double refraction4 ,it may be used to distinguish those stones which are doubly refracting from those which are not4 ,for example1 in the case of a stone which is doubly refracting to a strong degree1 such as a peridot 7the lighter yellowish-green chrysolite is the same material and behaves similarly toward light71 the separation of the light is so marked that the edges of the rear facets1 as seen through the table1 appear double when viewed through a lens4 ,a zircon will also similarly separate light and its rear facets also appear double-lined as seen with a lens from the table of the stone4 ,the rarer stones1 sphene and epidote1 likewise exhibit this property markedly4 ,some colorless zircons1 when well cut1 so closely resemble diamonds that even an expert might be deceived1 if caught off his guard1 but this simple test of looking for the doubled lines at the back of the stone would alone serve to distinguish the two stones4 ,illustration3 ,,fig4 #b4 ,a ,,simple ,,but ,,very ,,valuable ,,test ,,for ,,the ,,kind ,,of ,,refraction ,,of ,a ,,cut ,,stone4 ,in the case of most of the other doubly refracting stones the degree of separation is much less than in peridot and zircon1 and it takes a well-trained and careful eye to detect the doubling of the lines4 ,here a very simple device will serve to assist the eye in determining whether a cut stone is singly or doubly refracting4 ,expose the stone to direct sunlight and hold an opaque white card a few inches from the stone1 in the direction of the sun1 so as to get the bright reflections from within the stone reflected onto the card4 ,if the material is singly refractive 7as in the case of diamond1 garnet1 spinel1 and glass71 single images of each of the reflecting facets will appear on the card1 but if doubly refracting--even if slightly so--double images will appear4 ,when the stone is slightly moved1 these pairs of reflections will travel together as pairs and not tend to separate4 ,the space between the two members of each pair of reflections serves to give a rough idea of the degree of the double refraction of the material if compared with the space between members in the case of some other kind of stone held at the same distance from the card4 ,thus zircon separates the reflections widely4 ,aquamarine1 which is feebly doubly refracting1 separates them but slightly4 ,it will be seen at once that we have here a very easily applied test and one that requires no costly apparatus4 ,it is1 furthermore1 a sure test1 after a little practice4 ,for example1 if one has something that looks like a fine emerald1 but that may be glass1 all one need to do is to expose it in the sun1 as above indicated4 ,if real emerald1 double images will be had 7very close together1 because emerald is but feebly doubly refracting74 ,if glass1 the images on the card will be single4 ,similarly1 ruby can at once be distinguished from even the finest garnet or ruby spinel1 as the last two are singly refracting4 ,so1 too1 are glass imitations of ruby and ruby doublets 7which consist of glass and garnet74 ,this test cannot injure the stone1 it may be applied to mounted stones1 and it is reliable4 ,for stones of very deep color this test may fail for lack of sufficiently brilliant reflections4 ,in such a case hold the card beyond the stone and let the sunlight shine through the stone onto the card1 observing whether the spots of light are single or double4 ,the table below gives the necessary information as to which stones show double and which single refraction4 ,,table ,,giving ,,character ,,of ,,refraction ,,in ,,the ,,principal ,,gems ,refraction ,single3 ,diamond ,garnet 7all types7 ,spinel ,opal ,glass ,difference between highest and lowest refractive indices ,refraction ,double3 ,sphene 4#jhd ,zircon 4#jec ,benitoite 4#jdg ,peridot or chrysolite 4#jch ,epidote 4#jca ,tourmaline 4#jbj ,kunzite 4#jae ,ruby and sapphire 4#jji ,topaz 7precious7 4#jji ,amethyst and quartz topaz 4#jji ,emerald and aquamarine 4#jjg ,chrysoberyl 4#jjg ,the student should now put into practice the methods suggested in this lesson4 ,look first for the visible doubling of the lines of the back facets in peridot 7or chrysolite72 then in zircon2 then in some of the less strongly doubly refracting stones2 then try the sunlight-card method with genuine stones and with doublets and imitations until you can tell every time whether you are dealing with singly or doubly refracting material4 ,when a stone of unknown identity comes along1 try the method on it and thus assign it as a first step to one or the other class4 ,other tests will then be necessary to definitely place it4 ,,differences ,,in ,,refraction ,,due ,,to ,,crystal ,,form4 ,the difference in behavior toward light of the singly and doubly refracting minerals depends upon the crystal structure of the mineral4 ,all gems whose crystals belong in the cubic system are singly refracting in all directions3 ,in the case of some other systems of crystals the material may be singly refracting in one or in two directions1 but doubly refracting in other directions4 ,no attention need be paid to these complications1 however1 when using the sunlight-card method with a cut stone1 for in such a case the light in its course within the stone will have crossed the material in two or more directions1 and the separation and consequent doubling of image will be sure to result4 ,for those who wish to study double refraction more in detail1 ,chapter ,,vi41 pages #dj-eb1 of ,g4 ,f4 ,herbert-,smith's ,gem-,stones will serve admirably as a text4 ,as an alternative any text-book on physics will answer4 ,,lesson ,,iv ,,absorption ,,and ,,dichroism ,,cause ,,of ,,color ,,in ,,minerals4 ,in ,lesson ,,iii4 we saw that many gem materials cause light that enters them to divide and take two paths within the material4 ,now all transparent materials absorb light more or less2 that is1 they stop part of it1 perhaps converting it into heat1 and less light emerges than entered the stone4 ,if light of all the rainbow colors 7red1 orange1 yellow1 green1 blue1 violet7 is equally absorbed1 so that there is the same relative amount of each in the light that comes out as in the light that went into a stone1 we say that the stone is a white stone2 that is1 it is not a colored stone4 ,if1 however1 only blue light succeeds in getting through1 the rest of the white light that entered being absorbed within1 we say that we have a blue stone4 ,similarly1 the color of any transparent material depends upon its relative degree of absorption of each of the colors in white light4 ,that color which emerges most successfully gives its name to the color of the stone4 ,thus a ruby is red because red light succeeds in passing through the material much better than light of any other color4 ,,unequal ,,absorption ,,causes ,,dichroism4 ,all that has been said so far applies equally well to both singly and doubly refracting materials1 but in the latter sort it is frequently the case1 in those directions in which light always divides1 that the absorption is not equal in the two beams of light 7one is called the ordinary ray and the other the extraordinary ray74 ,for example1 in the case of a crystal of ruby1 if white light starts to cross the crystal1 it not only divides into an ordinary ray and an extraordinary ray1 but the absorption is different in the two cases1 and the two rays emerge of different shades of red4 ,with most rubies one ray emerges purplish red1 the other yellowish red4 ,it will at once be seen that if the human eye could distinguish between the two rays1 we would have here a splendid method of determining many precious stones4 ,unfortunately1 the eye does not analyze light1 but rather blends the effect so that the unaided eye gives but a poor means of telling whether or not a stone exhibits twin colors1 or dichroism1 as it is called4 7,the term signifies two colors47 ,a well-trained eye can1 however1 by viewing a stone in several different positions1 note the difference in shade of color caused by the differential absorption4 ,,the ,,dichroscope4 ,now1 thanks to the scientific workers1 there has been devised a relatively simple and comparatively inexpensive instrument called the dichroscope1 which enables one to tell almost at a glance whether a stone is or is not dichroic4 ,the construction is indicated in the accompanying drawing and description4 ,illustration3 ,,the ,,dichroscope4 ,illustration3 ,,fig4 #c4 ,a1 simple lens2 ,b1 piece of ,iceland spar with glass prisms on ends to square them up2 ,c1 square hole4 ,illustration3 ,,fig4 #d4 ,if the observer looks through the lens 7,a7 toward a bright light1 as1 for example1 the sky1 he apparently sees two square holes1 ,fig4 #d4 ,what has happened is that the light passing through the square hole 7,c of ,fig4 #c7 has divided in passing through the strongly doubly refracting ,iceland spar 7,b of ,fig4 #c7 and two images of the square hole are thus produced4 ,if now a stone that exhibits dichroism is held in front of the square hole and viewed toward the light1 two images of the stone are seen1 one due to its ordinary ray 7which1 as was said above1 will have one color71 and the other due to its extraordinary ray 7which will have a different color or shade of color71 thus the color of the two squares will be different4 ,with a singly refracting mineral1 or with glass1 or with a doubly refracting mineral when viewed in certain directions of the crystal 7which do not yield double refraction7 the colors will be alike in the two squares4 ,thus to determine whether a red stone is or is not a ruby 7it might be a garnet or glass or a doublet1 all of which are singly refracting and hence can show no dichroism71 hold the stone before the hole in the dichroscope and note whether or not it produces twin colors4 ,if there seems to be no difference of shade turn the stone about1 as it may have accidentally been placed so that it was viewed along its direction of single refraction4 ,if there is still no dichroism it is not a ruby4 7,note4--,scientific rubies exhibit dichroism as well as natural ones1 so this test will not distinguish them47 ,a dichroscope may be had for from seven to ten dollars1 according to the make1 and everyone who deals in colored stones should own and use one4 ,not all stones that are doubly refracting exhibit dichroism4 ,white stones of course cannot exhibit it even though doubly refracting1 and some colored stones1 though strongly doubly refracting1 do not exhibit any noticeable dichroism4 ,the zircon1 for example1 is strongly doubly refracting1 but shows hardly any dichroism4 ,the test is most useful for emerald1 ruby1 sapphire1 tourmaline1 kunzite and alexandrite1 all of which show marked dichroism4 ,it is of little use to give here the twin colors in each case as the shades differ with different specimens1 according to their depth and type of color4 ,the deeper tinted stones of any species show the effect more markedly than the lighter ones4 ,the method is rapid and easy--it can be applied to mounted stones as well as to loose ones1 and it cannot injure a stone4 ,the student should1 if possible1 obtain the use of a dichroscope and practice with it on all sorts of stones4 ,he should especially become expert in distinguishing between rubies1 sapphires1 and emeralds1 and their imitations4 ,the only imitation 7scientific rubies and sapphires are not here classed as imitations71 which is at all likely to deceive one who knows how to use the dichroscope is the emerald triplet1 made with real 7but pale7 beryl above and below1 with a thin strip of green glass between4 ,as beryl is doubly refracting to a small degree1 and dichroic1 one might perhaps be deceived by such an imitation if not careful4 ,however1 the amount of dichroism would be less in such a case than in a true emerald of as deep a color4 ,those who wish to study further the subject of dichroism should see ,gem-,stones1 by ,g4 ,f4 ,herbert-,smith1 ,chapter ,,vii41 pp4 #ec-ei1 or see ,a ,handbook of ,precious ,stones1 by ,m4 ,d4 ,rothschild1 ,putnam's1 pp4 #ad-af4 ,,lesson ,v ,,specific ,,gravity ,the properties so far considered as serving to distinguish precious stones have all depended upon the behavior of the material toward light4 ,these properties were considered first because they afford1 to those acquainted with their use1 very rapid and sure means of classifying precious stones4 ,,density ,,of ,,minerals4 ,we will next consider an equally certain test1 which1 however1 requires rather more time1 apparatus1 and skill to apply4 ,each kind of precious stone has its own density4 ,that is1 if pieces of different stones were taken all of the same size1 the weights would differ1 but like-sized pieces of one and the same material always have the same weight4 ,it is the custom among scientists to compare the densities of substances with the density of water4 ,the number which expresses the relation between the density of any substance and the density of water is called the specific gravity number of the substance4 ,for example1 if1 size for size1 a material1 say diamond1 is #c4ea times as heavy as water1 its specific gravity is #c4ea4 ,it will be seen that since each substance always has1 when pure1 the same specific gravity1 we have here a means of distinguishing precious stones4 ,it is very seldom1 if ever1 the case that we find any two precious stones of the same specific gravity4 ,a few stones have nearly the same specific gravities1 and in such cases it is well to apply other tests also4 ,in fact one should always make sure of a stone by seeing that two or three different tests point to the same species4 ,we must next find out how to determine the specific gravity of a precious stone4 ,if the shape of a stone were such that the volume could be readily calculated1 then one could easily compare the weight with the volume or with the weight of the same volume of water1 and thus get the specific gravity 7for a specific gravity number really tells how much heavier a piece of material is than the same volume of water74 ,unfortunately the form of most precious stones is such that it would be very difficult to calculate the volume from the measurements1 and the latter would be hard to make accurately with small stones4 ,to avoid these difficulties the following ingenious method has been devised3 ,if a stone is dropped into water it pushes aside1 or displaces1 a body of water exactly equal in volume to itself4 ,if the water thus displaced were caught and weighed1 and the weight of the stone then divided by the weight of the water displaced1 we would have the specific gravity number of the stone4 ,this is precisely what is done in getting the specific gravity of small stones4 ,to make sure of getting an accurate result for the weight of water displaced the following apparatus is used4 ,illustration3 ,,fig4 #e4 ,a1 ,flask-like ,bottle2 ,b1 ,indicates ,ground ,glass ,stopper2 ,c1 ,shows ,hole ,drilled through ,stopper4 ,,the ,,specific ,,gravity ,,bottle4 ,a small flask-like bottle 7see ,fig4 #e7 is obtained4 ,this has a tightly fitting ground glass stopper 7,b74 ,the stopper has a small hole 7,c7 drilled through it lengthwise4 ,if the bottle is filled with water1 and the stopper dropped in and tightened1 water will squirt out through the small hole in the stopper4 ,on wiping off stopper and bottle we have the bottle exactly full of water4 ,if now the stopper is removed1 the stone to be tested 7which must of course be smaller than the neck of the bottle7 dropped in1 and the stopper replaced1 exactly as much water will squirt out as is equal in volume to the stone that was dropped in4 ,if we had weighed the full bottle with the stone on the pan beside it1 and then weighed the bottle with the stone inside it we could now1 by subtracting the last weight from the first1 find out how much the water1 that was displaced1 weighed4 ,this is precisely the thing to do4 ,the weight of the stone being known we now have merely to divide the weight of the stone by the weight of the displaced water1 and we have the specific gravity number4 ,reference to a table of specific gravities of precious stones will enable us to name our stone4 ,such a table follows this lesson4 ,a ,,sample ,,calculation4 ,the actual performance of the operation1 if one is skilled in weighing1 takes less time than it would to read this description4 ,at first one will be slow1 and perhaps one should read and re-read this lesson1 making sure that all the ideas are clear before trying to put them in practice4 ,a sample calculation may help make the matter clearer1 so one is appended3 ,weight of bottle stone 7outside7 #ec4ea carats ,weight of bottle stone 7inside7 #eb4ea carats ------------ ,weight of water displaced #a4jj carat ------------ ,weight of stone #c4ea carats ,weight of stone #c4ea ,specific gravity --------------- ---- #c4ea ,sp4 g4 ,weight of water #a4jj ,in this case the specific gravity being #c4ea1 the stone is probably diamond 7see table71 but might be precious topaz1 which has nearly the same specific gravity4 ,it is assumed that the jeweler will weigh in carats1 and that his balance is sensitive to 4#ja carat4 ,with such a balance1 and a specific gravity bottle 7which any scientific supply house will furnish for less than #a7 results sufficiently accurate for the determination of precious stones may be had if one is careful to exclude air bubbles from the bottle1 and to wipe the outside of the bottle perfectly dry before each weighing4 ,the bottle should never be held in the warm hands1 or it will act like a thermometer and expand the water up the narrow tube in the stopper1 thus leading to error4 ,a handkerchief may be used to grasp the bottle4 ,,table ,,of ,,specific ,,gravities ,,of ,,the ,,principal ,,gem ,,materials ,beryl 7,emerald7 #b4gd ,chrysoberyl 7,alexandrite7 #c4gc ,corundum 7,ruby1 sapphire1 ,oriental topaz7 #d4jc ,diamond #c4eb ,garnet 7,pyrope7 #c4gh 7,hessonite7 #c4fa 7,demantoid1 known in the trade as ,olivine7 #c4hd 7,almandite7 #d4je ,opal #b4ae ,peridot #c4dj ,quartz 7,amethyst1 common topaz7 #b4ff ,spinel 7,rubicelle1 ,balas ruby7 #c4fj ,spodumene 7,kunzite7 #c4ah ,topaz 7precious7 #c4ec ,tourmaline #c4aj ,turquoise #b4hb ,zircon1 lighter variety #d4bj heavier variety #d4fi ,for a more complete and scientific discussion of specific gravity determination see ,gem-,stones1 by ,g4 ,f4 ,herbert-,smith1 ,chapter ,,viii41 pp4 #fc-gg2 or see1 ,a ,handbook of ,precious ,stones1 by ,m4 ,d4 ,rothschild1 pp4 #ba-bg1 for an excellent account with illustrations2 or see any physics text-book4 ,,lesson ,,vi ,,specific ,,gravity ,,determinations ,,weighing ,a ,,gem ,,in ,,water4 ,in the previous lesson it was seen that the identity of a precious stone may be found by determining its specific gravity1 which is a number that tells how much heavier the material is than a like volume of water4 ,it was not explained1 however1 how one would proceed to get the specific gravity of a stone too large to go in the neck of a specific gravity bottle4 ,in the latter case we resort to another method of finding how much a like volume of water weighs4 ,if the stone1 instead of being dropped into a perfectly full bottle of water 7which then overflows71 be dropped into a partly filled glass or small beaker of water1 just as much water will be displaced as though the vessel were full1 and it will be displaced upward as before1 for lack of any other place to go4 ,consequently its weight will tend to buoy up or float the stone by trying to get back under it1 and the stone when in water will weigh less than when in air4 ,anyone who has ever pulled up a small anchor when out fishing from a boat will recognize at once that this is the case1 and that as the anchor emerges from the water it seems to suddenly grow heavier4 ,not only does the stone weigh less when in the water1 but it weighs exactly as much less as the weight of the water that was displaced by the stone 7which has a volume equal to the volume of the stone74 ,if we weigh a stone first in the air1 as usual1 and then in water 7where it weighs less71 and then subtract the weight in water from the weight in air we will have the loss of weight in water1 and this equals the weight of an equal volume of water1 which is precisely what we got by our bottle method4 ,we now need only divide the weight in air by the loss of weight in water1 and we shall have the specific gravity of the stone4 ,illustration3 ,,fig4 #f4 ,to actually weigh the stone in water we must use a fine wire to support the stone4 ,we must first find how much this wire itself weighs 7when attached by a small loop to the hook that supports the balance pan and trailing partly in the water1 as will be the case when weighing the stone in water74 ,this weight of the wire must of course be deducted to get the true weight of the stone in water4 ,the beaker of water is best supported by a small table that stands over the balance pan4 ,one can easily be made out of the pieces of a cigar box4 7,see ,fig4 #f47 ,the wire that is to support the stone should have a spiral at the bottom in which to lay the gem1 and this should be so placed that the latter will be completely submerged at all times1 but not touching bottom or sides of the beaker4 ,example of data1 and calculation1 when getting specific gravity by the method of weighing in water3 ,weight of stone #d4jb carats ----------- ,weight of stone 7plus wire7 in water #c4cb carats ,weight of wire 4#cj carat ----------- ,true weight of stone in water #c4jb carats ----------- ,loss of weight in water #a4jj carat ,weight of stone #d4jb ,specific gravity --------------- ---- #d4jb ,loss in water #a4jj ,here the specific gravity1 #d4jb would indicate some corundum gem 7ruby or sapphire71 and the other characters would indicate at once which it was4 ,the student who means to master the use of the two methods given in ,lessons ,v4 and ,,vi4 should proceed to practice them with stones of known specific gravities until he can at least get the correct result to the first decimal place4 ,it is not to be expected that accurate results can be had in the second decimal place1 with the balances usually available to jewelers4 ,when the learner can determine specific gravities with some certainty he should then try unknown gems4 ,the specific gravity method is of especial value in distinguishing between the various colorless stones1 as1 for example1 quartz crystal1 true white topaz1 white sapphire1 white or colorless beryl1 etc4 ,these are all doubly refractive1 have no color1 and hence no dichroism1 and unless one has a refractometer to get the refractive index1 they are difficult to distinguish4 ,the specific gravities are very different1 however1 and readily serve to distinguish them4 ,it should be added that the synthetic stones show the same specific gravities as their natural counterparts1 so that this test does not serve to detect them4 ,where many gems are to be handled and separated by specific gravity determinations1 perhaps the best way to do so is to have several liquids of known specific gravity and to see what stones will float and what ones will sink in the liquids4 ,methylene iodide is a heavy liquid 7sp4 g4 #c4cb71 on which a quartz-topaz1 for example1 sp4 g4 #b4ff1 would float1 but a true topaz1 sp4 g4 #c4ec1 would sink in it4 ,by diluting methylene iodide with benzol 7sp4 g4 #j4hh7 any specific gravity that is desired may be had 7between the two limits #j4hh and #c4cb74 ,specimens of known specific gravity are used with such liquids and their behavior 7as to whether they sink or float1 or remain suspended in the liquid17 indicates the specific gravity of the liquid4 ,an unknown stone may then be used and its behavior noted and compared with that of a known specimen1 whereby one can easily find out whether the unknown is heavier or lighter than the known sample4 ,an excellent account of the detail of this method is given in ,g4 ,f4 ,herbert-,smith's ,gem-,stones1 pages #fd-ga1 of ,chapter ,,viii41 and various liquids are there recommended4 ,it is doubtful if the practical gem dealer would find these methods necessary in most cases4 ,where large numbers of many different unknown gems have to be determined it would pay to prepare1 and standardize1 and use such solutions4 ,,lesson ,,vii ,,luster ,,and ,,other ,,reflection ,,effects ,by the term luster we refer to the manner and degree in which light is reflected from the surface of a material4 ,surfaces of the same material1 but of varying degrees of smoothness would1 of course1 vary in the vividness of their luster1 but the type of variation that may be made use of to help distinguish gems1 depends upon the character of the material more than upon the degree of smoothness of its surface4 ,just as silk has so typical a luster that we speak of it as silky luster1 and just as pearl has a pearly luster1 so certain gems have peculiar and characteristic luster4 ,the diamond gives us a good example4 ,most diamond dealers distinguish between real and imitation diamonds at a glance by the character of the luster4 ,that is the chief1 and perhaps the only property1 that they rely upon for deciding the genuineness of a diamond1 and they are fairly safe in so doing1 for1 with the exception of certain artificially decolorized zircons1 no gem stone is likely to deceive one who is familiar with the luster of the diamond4 ,it is not to be denied that a fine white zircon1 when finely cut1 may deceive even one who is familiar with diamonds4 ,the author has fooled many diamond experts with an especially fine zircon1 for the luster of zircon does approach1 though it hardly equals1 that of the diamond4 ,rough zircons are frequently mistaken for diamonds by diamond prospectors1 and even by pickers in the mines1 so that some care should be exercised in any suspicious case1 and one should not then rely solely on the luster4 ,however1 in most cases in the trade there is almost no chance of the unexpected presence of a zircon and the luster test is usually sufficient to distinguish the diamond4 7,zircons are strongly doubly refractive1 as was said in ,lesson ,,iii4 on ,double ,refraction1 and with a lens the doubling of the back lines may be seen47 ,,adamantine ,,luster4 ,the luster of a diamond is called adamantine 7the adjective uses the ,greek name for the stone itself74 ,it is keen and cold and glittering1 having a metallic suggestion4 ,a very large per cent4 of the light that falls upon the surface of a diamond at any low angle is reflected1 hence the keenness of its luster4 ,if a diamond and some other white stone1 say a white sapphire1 are held so as to reflect at the same time images of an incandescent light into the eye of the observer1 such a direct comparison will serve to show that much more light comes to the eye from the diamond surface than from the sapphire surface4 ,the image of the light filament1 as seen from the diamond1 is much keener than as seen from the sapphire4 ,the same disparity would exist between the diamond and almost any other stone4 ,zircon comes nearest to having adamantine luster of any of the other gems4 ,the green garnet that is called olivine in the trade also approaches diamond in luster1 hence the name demantoid1 or diamond like1 sometimes applied to it4 ,,vitreous ,,luster4 ,the other stones nearly all have what is called vitreous luster 7literally1 glass like71 yet owing to difference of hardness1 and consequent minute differences in fineness of surface finish1 the keenness of this vitreous luster varies slightly in different stones1 and a trained eye can obtain clues to the identity of certain stones by means of a consideration of the luster4 ,garnets1 for example1 being harder than glass1 take a keener polish1 and a glance at a doublet 7of which the hard top is usually garnet and the base of glass7 will show that the light is better reflected from the garnet part of the top slope than from the glass part4 ,this use of luster affords the quickest and surest means of detecting a doublet4 ,one can even tell a doublet inside a show window1 although the observer be outside on the sidewalk1 by moving to a position such that a reflection from the top slope of the stone is to be had4 ,when a doublet has a complete garnet top no such direct comparison can be had1 but by viewing first the top luster1 and then the back luster1 in rapid succession1 one can tell whether or not the stone is a doublet4 ,,oily ,,luster4 ,certain stones1 notably the peridot 7or chrysolite7 and the hessonite 7or cinnamon stone71 have an oily luster4 ,this is possibly due to reflection of light that has penetrated the surface slightly and then been reflected from disturbed layers beneath the surface4 ,at any rate1 the difference in luster may be made use of by those who have trained their eyes to appreciate it4 ,much practice will be needed before one can expect to tell at a glance when he has a peridot 7or chrysolite7 by the luster alone1 but it will pay to spend some spare time in studying the luster of the various stones4 ,a true1 or precious topaz1 for example1 may be compared with a yellow quartz-topaz1 and owing to the greater hardness of the true topaz1 it will be noted that it has a slightly keener luster than the other stone1 although both have vitreous luster4 ,similarly the corundum gems 7ruby and sapphire71 being even harder than true topaz1 take a splendid surface finish and have a very keen vitreous luster4 ,turquoise has a dull waxy luster1 due to its slight hardness4 ,malachite1 although soft1 has1 perhaps because of its opacity1 a keen and sometimes almost metallic luster4 ,one may note the luster rapidly1 without apparatus and without damage to the stone4 ,we thus have a test which1 while it is not conclusive except in a very few cases1 will supplement and serve to confirm other tests1 or perhaps1 if used at first1 will suggest what other tests to apply4 ,another optical effect that serves to distinguish some stones depends upon the reflection of light from within the material due to a certain lack of homogeneity in the substance4 ,,cause ,,of ,,color ,,in ,,the ,,opal4 ,thus the opal is distinguished by the prismatic colors that emerge from it owing to the effect of thin layers of material of slightly different density1 and hence of different refractive index from the rest of the material4 ,these thin films act much as do soap-bubble films1 to interfere with light of certain wave lengths1 but to reflect certain other wave lengths and hence certain colors4 ,again1 in some sapphires and rubies are found minute1 probably hollow1 tube-like cavities1 arranged in three sets in the same positions as the transverse axes of the hexagonal crystal4 ,the surfaces of these tubes reflect light so as to produce a six-pointed star effect1 especially when the stone is properly cut to a high1 round cabochon form1 whose base is parallel to the successive layers of tubes4 ,,starstones1 ,,moonstones1 ,,cat',s-,,eyes4 ,in the moonstone we have another sort of effect1 this time due to the presence of hosts of small twin crystal layers that reflect light so as to produce a sort of moonlight-on-the-water appearance within the stone when the latter is properly cut1 with the layers of twin crystals parallel to its base4 ,ceylon-cut moonstones are frequently cut to save weight1 and may have to be recut to properly place the layers so that the effect may be seen equally over all parts of the stone1 as set4 ,cat's-eye and tiger's-eye owe their peculiar appearance to the presence1 within them1 of many fine1 parallel1 silky fibers4 ,the quartz cat's-eye was probably once an asbestos-like mineral1 whose soft fibers were replaced by quartz in solution1 and the latter1 while giving its hardness to the new mineral1 also took up the fibrous arrangement of the original material4 ,the true chrysoberyl cat's-eye also has a somewhat similar fibrous or perhaps tubular structure4 ,such stones1 when cut en cabochon1 show a thin sharp line of light running across the center of the stone 7when properly cut with the base parallel to the fibers74 ,this is due to reflection of light from the surfaces of the parallel fibers4 ,the line of light runs perpendicularly to the fibers4 ,in these cases 7opals1 starstones1 moonstones1 and cat's-eyes7 the individual stone is usually easily distinguished from other kinds of stones by its peculiar behavior towards light4 ,however1 it must be remembered that other species than corundum furnish starstones 7amethyst and other varieties of quartz1 for example71 so that it does not follow that any starstone is a corundum gem4 ,also the more valuable chrysoberyl cat's-eye may be confused with the cheaper quartz cat's-eye unless one is well acquainted with the respective appearances of the two varieties4 ,whenever there is any doubt other tests should be applied4 ,for further account of luster and other types of reflection effects see ,gem-,stones1 by ,g4 ,f4 ,herbert-,smith1 ,chapter ,v41 pp4 #cg-ci1 or ,a ,handbook of ,precious ,stones1 ,m4 ,d4 ,rothschild1 pp4 #ag1 #ah4 ,,lesson ,,viii ,,hardness ,another property by means of which one may distinguish the various gems from each other is hardness4 ,by hardness is meant the ability to resist scratching4 ,the term hardness should not be taken to include toughness1 yet it is frequently so understood by the public4 ,most hard stones are more or less brittle and would shatter if struck a sharp blow4 ,other hard stones have a pronounced cleavage and split easily in certain directions4 ,true hardness1 then1 implies merely the ability to resist abrasion 7i4 e41 scratching74 ,now1 not only is hardness very necessary in a precious stone in order that it may receive and keep a fine polish1 but the degree in which it possesses hardness as compared with other materials of known hardness may be made use of in identifying it4 ,no scale of absolute hardness has ever come into general use1 but the mineralogist ,mohs many years ago proposed the following relative scale1 which has been used very largely3 ,,mohs',s ,,scale ,,of ,,hardness4 ,diamond1 the hardest of all gems1 was rated as #aj by ,mohs4 ,this rating was purely arbitrary4 ,mohs might have called it #ajj or #a with equal reason4 ,it was merely in order to represent the different degrees of hardness by numbers1 that he picked out the number #aj to assign to diamonds4 ,sapphire 7and ruby7 ,mohs called #i1 as being next to diamond in hardness4 ,true topaz 7precious topaz7 he called #h4 ,quartz 7amethyst and quartz topaz7 was given the number #g4 ,feldspar 7moonstone7 was rated #f1 the mineral apatite #e1 fluorspar #d1 calcite #c1 gypsum #b1 and talc #a4 ,it may be said here that any mineral in this series1 that is of higher number than any other1 will scratch the other4 ,thus diamond 7#aj7 will scratch all the others1 sapphire 7#i7 will scratch any but diamond1 topaz 7#h7 will scratch any but diamond and sapphire1 and so on4 ,it must not be thought that there is any regularity in the degrees of hardness as expressed by these numbers4 ,the intervals in hardness are by no means equal to the differences in number4 ,thus the interval between diamond and sapphire1 although given but one number of difference1 is probably greater than that between sapphire 7#i7 and talc 7#a74 ,the numbers thus merely give us an order of hardness4 ,many gem minerals are1 of course1 missing from this list1 and most of the minerals from #e down to #a are not gem minerals at all4 ,few gem materials are of less hardness than #g1 for any mineral less hard than quartz 7#g7 will inevitably be worn and dulled in time by the ordinary road dust1 which contains much powdered quartz4 ,in testing a gem for hardness the problem consists in finding out which of the above minerals is most nearly equal in hardness to the unknown stone4 ,any gem that was approximately equal in hardness to a true topaz 7#h7 would also be said to be of hardness #h4 ,thus spinel is of about the same hardness as topaz and hence is usually rated as #h in hardness4 ,similarly opal1 moonstone1 and turquoise are of about the same hardness as feldspar and are all rated #f4 ,frequently stones will be found that in hardness are between some two of ,mohs's minerals4 ,in that case we add one half to the number of the softer mineral2 thus1 peridot1 benitoite1 and jade 7nephrite7 are all softer than quartz 7#g7 but harder than feldspar 7#f72 hence we say they are #f-a_/b in hardness4 ,beryl 7aquamarine and emerald71 garnet 7almandine71 and zircon are rated #g-a_/b in hardness1 being softer than true topaz but harder than quartz4 ,a table of the hardness of most of the commonly known gem-stones follows this lesson4 ,having now an idea of what hardness means and how it is expressed1 we must next inquire how one may make use of it in identifying unknown gems4 ,,how ,,to ,,apply ,,the ,,hardness ,,test4 ,in the first place1 it is necessary to caution the beginner against damaging a fine gem by attempting to test its hardness in any but the most careful manner4 ,the time-honored file test is really a hardness test and serves nicely to distinguish genuine gems1 of hardness #g or above1 from glass imitations4 ,a well-hardened steel file is of not quite hardness #g1 and glass of various types while varying somewhat averages between #e and #f4 ,hence1 glass imitations are easily attacked by a file4 ,to make the file test use only a very fine file and apply it with a light but firm pressure lengthwise along the girdle 7edge7 of the unset stone4 ,if damage results it will then be almost unnoticeable4 ,learn to know the feel of the file as it takes hold of a substance softer than itself4 ,also learn the sound4 ,if applied to a hard stone a file will slip on it1 as a skate slips on ice4 ,it will not take hold as upon a softer substance4 ,if the stone is set1 press a sharp corner of a broken-ended file gently against a back facet1 preferably high up toward the girdle1 where any damage will not be visible from the front1 and move the file very slightly along the surface1 noting by the feel whether or not it takes hold and also looking with a lens to see if a scratch has been made4 ,do not mistake a line of steel1 left on a slightly rough surface1 for a true scratch4 ,frequently on an unpolished girdle of real gem material the file will leave a streak of steel4 ,similarly when using test minerals in accordance with what follows do not mistake a streak of powder from the yielding test material1 for a true scratch in the material being tested4 ,the safe way is to wipe the spot thus removing any powder4 ,a true scratch will1 of course1 persist4 ,a doublet1 being usually constructed of a garnet top and a glass back1 may resist a file at the girdle if the garnet top covers the stone to the girdle1 as is sometimes the case1 especially in the smaller sizes4 ,in this case the back must be tested4 ,one should never pass a file rudely across the corners or edges of the facets on any stone that may be genuine1 as such treatment really amounts to a series of light hammer blows1 and the brittleness of most gem stones would cause them to yield1 irrespective of their hardness4 ,it should be remembered that some genuine stones are softer than a file1 so that it will not do to reject as worthless any material that is attacked by a file4 ,lapis lazuli 7#e71 sphene 7#e71 opal 7#f71 moonstone 7#f71 amazonite 7#f71 turquoise 7#f71 peridot 7#f-a_/b71 demantoid garnet 7#f-a_/b7 7the olivine of the trade71 and jade 7nephrite7 7#f-a_/b71 are all more or less attacked by a file4 ,,table ,,of ,,hardness ,,of ,,the ,,principal ,,gem-,,stones #aj4 ,diamond4 #i-a_/b4 7,carborundum47 #i4 ,sapphire and ruby 7also all the color varieties of sapphire74 #h-a_/b4 ,chrysoberyl 7alexandrite74 #h4 ,true topaz and spinel 7rubicelle1 balas ruby74 #g-a_/b4 ,emerald1 aquamarine1 beryl1 ,morganite1 zircon 7jacinth and true hyacinth and jargoon71 almandine garnet4 #g-a_/d4 ,pyrope garnet 7,arizona ruby1 cape ruby71 hessonite garnet 7cinnamon stone71 tourmaline 7various colors vary from #g to #g-a_/b71 kunzite 7#g74 #g4 ,amethyst1 various quartz gems1 quartz topaz1 jade 7jadeite74 #f-a_/b4 ,peridot 7chrysolite71 demantoid garnet 7olivine71 jade 7nephrite74 #f4 ,opal1 moonstone1 turquoise4 #e4 ,lapis lazuli4 ,,lesson ,,ix ,,hardness--,continued ,,minerals ,,used ,,in ,,testing ,,hardness4 ,for testing stones that are harder than a file the student should provide himself with the following set of materials3 #a4 ,a small crystal of carborundum4 7,most hardware stores have specimen crystals as attractive advertisements of carborundum as an abrasive material1 or the ,carborundum ,co41 ,niagara ,falls1 ,n4 ,y41 will supply one47 #b4 ,a small crystal of sapphire 7not of gem quality1 but it should be transparent and compact4 ,a pale or colorless ,montana sapphire can be had for a few cents of any mineral dealer74 #c4 ,a small true topaz crystal4 7,the pure white topaz of ,thomas ,mountain1 ,utah1 is excellent2 or white topaz from ,brazil or ,japan or ,mexico or ,colorado will do4 ,any mineral house can furnish small crystals for a few cents when not of specially fine crystallization47 #d4 ,a small quartz crystal4 7,this may be either amethyst or quartz-topaz or the common colorless variety4 ,the fine1 sharp1 colorless crystals from ,herkimer ,county1 ,n4 ,y41 are excellent4 ,these are very inexpensive47 #e4 ,a fragment of a crystal of feldspar4 7,common orthoclase feldspar1 which is frequently of a brownish pink or flesh color1 will do47 ,these five test stones represent the following degrees of hardness3 #a4 ,carborundum is harder than any gem material but diamond4 ,it will scratch sapphire and ruby1 which are rated #i in hardness1 hence we may call carborundum #i-a_/b if we wish4 ,it is1 however1 very much softer than diamond1 and the latter will scratch it upon the slightest pressure4 #b4 ,sapphire1 of hardness #i1 scratching any gem material except diamond4 #c4 ,true topaz1 of hardness #h4 ,it is scratched by sapphire 7and1 of course1 ruby71 also by chrysoberyl 7which is hence rated #h-a_/b71 but scratches most other stones4 ,spinel 7which is also rated as #h in hardness7 is really a bit harder than topaz4 #d4 ,quartz1 of hardness #g1 and scratched by all the previous stones but scratching those that were listed above as of less hardness than a file4 #e4 ,feldspar1 of hardness #f1 hence slightly softer than a file and yielding to it1 but scratching the stones likewise rated as #f when applied forcibly to them4 ,also scratching stones rated as less than #f on slight pressure4 ,we must next consider how these minerals may be safely used upon gem material4 ,obviously it would be far safer to use them upon rough gem material than upon cut stones4 ,however1 with care and some little skill1 one may make hardness tests without particular danger to fine cut material4 ,the way to proceed is to apply the cut stone 7preferably its girdle1 or if that is so set as not to be available1 a corner where several facets meet7 gently to the flat surface of one of the softer test stones1 drawing it lightly along the surface and noting the feel and looking to see if a scratch results4 ,if the test stone is scratched try the next harder test stone similarly4 ,do not attempt to use the test stone upon any valuable cut stone4 ,proceed as above until the gem meets a test stone that it does not attack4 ,its hardness is then probably equal to the latter and perhaps if pressed forcibly against it a slight scratch would result1 but it is not advisable to resort to heavy pressure4 ,a light touch should be cultivated in this work4 ,having now an indication as to the hardness of the unknown gem look up in the table of the previous lesson those gems of similar hardness and then by the use of some of the tests already given decide which of the stones of that degree of hardness you have4 ,never rely upon a single test in identifying a gem4 ,for further study of hardness and its use in testing gems see ,gem-,stones1 ,g4 ,f4 ,herbert-,smith1 ,chap4 ,,ix41 pp4 #gh-ha1 and table on p4 #cje2 or see ,a ,handbook of ,precious ,stones1 ,rothschild1 pp4 #ai1 #bj1 #ba4 ,,lesson ,x ,,dispersion ,another property which may be made use of in deciding the identity of certain gems is that called dispersion4 ,we have seen in ,lesson ,,ii4 that light in entering a stone from the air changes its path 7refraction71 and in ,lesson ,,iii4 it was explained that many minerals cause light that enters them1 to divide and proceed along two different paths 7double refraction74 ,now it is further true that light of the various colors 7red1 orange1 yellow1 green1 blue1 and violet7 is refracted variously--the violet being bent most sharply1 the red least1 and the other colors to intermediate degrees4 ,the cut 7,fig4 #g7 represents roughly and in an exaggerated manner the effect we are discussing4 ,illustration3 ,,fig4 #g4 ,now in a cut stone this separation of light of different colors1 or dispersion of light1 as it is called1 results in the reflection of each of the colors separately from the steep sloping back facets of the stone4 ,if almost any clear1 colorless facetted stone is placed in the sunlight and a card held before it to receive the reflections1 it will be seen that rainbow-like reflections appear on the card4 ,these spectra1 as they are called1 are caused by the dispersion of light4 ,with a diamond the spectra will be very brilliant and of vivid coloring1 and the red will be widely separated from the blue4 ,with white sapphire or white topaz1 or with rock crystal 7quartz71 the spectra will be less vivid--they will appear in pairs 7due to the double refraction of these minerals71 and the red and blue will be near together 7i4 e41 the spectra will be short74 ,this shortness in the latter cases is due to the small dispersive power of the three minerals mentioned4 ,paste 7lead glass7 gives fairly vivid spectra1 and they are single like those from diamond1 as glass is singly refracting4 ,the dispersion of the heavy lead glass approaches that of diamond4 ,the decolorized zircon 7jargoon7 has a dispersion well up toward that of diamond and gives fairly vivid spectra on a card1 but they are double1 as zircon is doubly refracting4 ,sphene 7a gem rarely seen in the trade7 and the demantoid garnet 7a green gem often called olivine in the trade7 both have very high dispersive power1 exceeding the diamond in this respect4 ,as they are both colored stones 7sphene is usually yellowish1 sometimes greenish or brown71 the vividness of their color-play is much diminished by absorption of light within them4 ,so also the color-play of a deeply colored fancy diamond is diminished by absorption4 ,,dispersion ,,as ,a ,,test ,,of ,,the ,,identity ,,of ,a ,,gem4 ,we may now consider how an acquaintance with the dispersive powers of the various stones can be used in distinguishing them4 ,if a stone has high dispersive power it will exhibit fire1 as it is called--i4 e41 the various colors will be so widely separated within the stone1 and hence reflected out so widely separated1 that they will fall on the eye 7as on the card above7 in separate layers1 and vivid flashes of red or yellow or other colors will be seen4 ,such stones as the white sapphire 7and others of small dispersion71 however1 while separating the various colors appreciably as seen reflected on a card1 do not sufficiently separate them to produce the fire effect when the light falls on the eye4 ,this is because the various colors1 being very near together in this case1 cross the eye so rapidly1 when the stone is moved1 that they blend their effect and the eye regards the light that thus falls upon it as white4 ,we have here a ready means of distinguishing the diamond from most other colorless gems4 ,the trained diamond expert relies 7probably unconsciously7 upon the dispersive effect 7or fire7 nearly as much as upon the adamantine luster1 in telling at a glance whether a stone is or is not a diamond4 ,of all colorless stones1 the only one likely to mislead the expert in this respect is the whitened zircon 7jargoon71 which has almost adamantine luster and in addition nearly as high dispersive power as diamond4 ,however1 zircon is doubly refracting 7strongly so71 and the division of the spectra which results 7each facet producing two instead of only one7 weakens the fire so that even the best zircon is a bit sleepy as compared with even an ordinary diamond4 ,in addition to providing a ready means of identifying the diamond1 a high degree of dispersion in a stone of pronounced color would lead one to consider sphene1 demantoid garnet 7if green71 and zircon 7which might be reddish1 yellowish1 brown1 or of other colors71 and if the stone did not agree with these in its other properties one should suspect glass4 ,a good way to note the degree of dispersion1 aside from the sunlight-card method1 is to look at the stone from the back while holding it up to the light 7daylight74 ,stones of high dispersive power will display vivid color play in this position4 ,glass imitations of rubies1 emeralds1 amethysts1 etc41 will display altogether too much dispersion for the natural gems4 ,in ,chap4 ,,iii41 p4 #bj1 of ,g4 ,f4 ,herbert-,smith's ,gem-,stones1 a brief account of dispersion is given4 ,college text-books on physics also treat of it1 and the latter give an account of how dispersion is measured and what is meant by a coefficient of dispersion4 ,most gem books say little about it1 but as we have seen above1 a knowledge of the matter can1 when supplemented by other tests1 be applied practically in distinguishing gems4 ,,lesson ,,xi ,,color ,in reserving to the last the property of color1 which many dealers in gems use first when attempting to identify a precious stone1 ,i have sought to point out the fact that a determination based solely upon color is very likely to be wrong4 ,so many mineral species are found in so many different colors that to attempt to identify any mineral species by color alone is usually to invite disaster4 ,the emerald1 alone among gems1 has1 when of fine color1 a hue that is not approached by any other species4 ,the color of the grass in the springtime fitly describes it4 ,yet even here the art of man has so closely counterfeited in glass the green of the emerald that one cannot be sure of his stone by color alone4 ,as was suggested earlier in these lessons1 the writer has several times recently had occasion to condemn as glass imitations stones for which high prices had been paid as genuine emeralds1 those who sold them having relied solely upon a trained eye for color4 ,,confusion ,,of ,,gems ,,due ,,to ,,similarity ,,of ,,color4 ,the same tendency to rely upon color causes many in the trade to call all yellow stones topaz whether the species be corundum 7oriental topaz71 true topaz 7precious topaz71 citrine quartz 7quartz topaz71 heliodor 7yellow beryl71 jacinth 7yellow zircon71 or what not4 ,similarly the public calls all red stones ruby4 ,thus we have cape ruby and ,arizona ruby 7pyrope garnet71 spinel ruby 7more properly ruby spinel71 ,siam ruby 7very dark red corundum71 ,ceylon ruby 7pale pinkish corundum71 rubellite 7pink tourmaline71 and lastly ,burmah ruby 7the fine blood-red corundum74 ,while it is true that color1 unless skillfully estimated and wisely used in conjunction with other properties1 is a most unreliable guide1 yet when thus used1 it becomes a great help and serves sometimes to narrow down the chase1 at the start1 to a very few species4 ,to thus make use of it requires an actual acquaintance with the various gem materials1 in their usual colors and shades and an eye trained to note and to remember minute differences of tint and shade4 ,the suggestions which follow as to usual colors of mineral species must then be used only with discretion and after much faithful study of many specimens of each of the species4 ,let us begin with the beginning color of the visible spectrum1 red1 and consider how a close study of shades of red can help in distinguishing the various red stones from each other4 ,in the first place we will inquire what mineral species are likely to furnish us with red stones4 ,omitting a number of rare minerals1 we have 7#a7 corundum ruby1 7#b7 garnet of various types1 7#c7 zircon1 7#d7 spinel1 7#e7 tourmaline4 ,these five minerals are about the only common species which give us an out-and-out red stone4 ,let us now consider the distinctions between the reds of these different species4 ,the red of the ruby1 whether dark 7,siam type71 blood red 7,burmah type71 or pale 7,ceylon71 is more pleasing usually than the red of any of the other species4 ,viewed from the back of the stone 7by transmitted light7 it is still pleasing4 ,it may be purplish1 but is seldom orange red4 ,also1 owing to the dichroism of the ruby the red is variable according to the changing position of the stone4 ,it therefore has a certain life and variety not seen in any of the others except perhaps in red tourmaline1 which1 however1 does not approach ruby in fineness of red color4 ,,red ,,stones ,,of ,,similar ,,shades4 ,the garnet1 on the other hand1 when of fire-red hue1 is darker than any but the ,siam ruby4 ,it is also more inclined to orange red or brownish red--and the latter is especially true when the stone is seen against the light 7by transmitted light74 ,its color then resembles that of a solution of iron such as is given as medicine4 ,the so-called almandine garnets 7those of purplish-red tint7 do not equal the true ruby in brightness of color and when held up to the light show more prismatic colors than the true ruby1 owing to the greater dispersion of garnet4 ,the color also lacks variety 7owing to lack of dichroism74 ,while a fine garnet may make a fair-looking ruby when by itself1 it looks inferior and dark when beside a fine ruby4 ,by artificial light1 too1 the garnet is dark as compared with the true ruby1 and the latter shows its color at a distance much more strongly than the garnet4 ,the red zircon1 or true hyacinth1 is rare4 7,many hessonite garnets are sold as hyacinths in the trade4 ,these are usually of a brownish red47 ,the red of the hyacinth is never equal to that of the ruby4 ,it is usually more somber1 and a bit inclined to a brownish cast4 ,the dispersion of zircon1 too1 is so large 7about #hg per cent4 of that of diamond7 that some little color-play is likely to appear along with the intrinsic color4 ,the luster too is almost adamantine while that of ruby is softer and vitreous4 ,although strongly doubly refracting1 the hyacinth shows scarcely any dichroism and thus lacks variety of color4 ,hence a trained eye will at once note these differences and not confound the stone with ruby4 ,spinels1 when red1 are almost always more yellowish or more purplish than fine corundum rubies4 ,they are also singly refracting and hence exhibit no dichroism and therefore lack variety of color as compared with true ruby4 ,some especially fine ones1 however1 are of a good enough red to deceive even jewelers of experience1 and one in particular that ,i have in mind has been the rounds of the stores and has never been pronounced a spinel1 although several experts have insisted that it was a scientific ruby4 ,the use of a dichroscope would have saved them that error1 for the stone is singly refracting4 ,spinels are usually clearer and more transparent than garnets and show their color better at a distance or when in a poor light4 ,tourmaline of the reddish variety 7rubellite7 is seldom of a deep red4 ,it is more inclined to be pinkish4 ,the dichroism of tourmaline is stronger than that of ruby and more obvious to the unaided eye4 ,the red of the rubellite should not deceive anyone who has ever seen a fine corundum ruby4 ,,yellow ,,stones ,considering next the stones of yellow color1 we have the following species to deal with3 7#a7 diamond1 7#b7 corundum1 7#c7 precious topaz1 7#d7 quartz1 7#e7 beryl1 7#f7 zircon1 7#g7 tourmaline4 ,,yellow ,,zircon ,,resembles ,,yellow ,,diamond4 ,here we have less opportunity to judge of the species by the color than was the case with the red stones4 ,the diamond1 of course1 is easy to tell1 not by the kind of yellow that it displays1 for it varies greatly in that respect1 but rather by its prismatic play blended with the intrinsic color4 ,its luster also gives an immediate clue to its identity4 ,it is necessary1 however1 to be sure that we are not being deceived by a yellow zircon1 for the latter has considerable fire and a keen luster4 ,its strong double refraction and its relative softness1 as well as its great density will serve to distinguish it4 ,of the other yellow stones1 the true or precious topaz is frequently inclined to a pinkish or wine yellow and many such stones lose all their yellow 7retaining their pink7 when gently heated4 ,the so-called pinked topazes are thus produced4 ,the yellow corundum rarely has a color that is at all distinctive4 ,as far as color goes the material might be yellow quartz1 or yellow beryl1 or yellow zircon1 or yellow tourmaline 7,ceylon type74 ,many of the yellowish tourmalines have a decidedly greenish cast 7greenish-yellow chrysoberyl might resemble these also74 ,however1 in general if one has a yellow stone to determine it will be safer to make specific gravity or hardness tests1 or both1 before deciding1 rather than to rely upon color4 ,,lesson ,,xii ,,color--,continued ,,green ,,stones ,let us first consider what mineral species are most likely to give us green stones4 ,omitting the semi-precious opaque or translucent stones we have3 #a4 ,grass-green beryl 7the emerald7 which is1 of course1 first in value among the green stones and first in the fine quality of its color4 #b4 ,tourmaline 7some specimens of which perhaps more nearly approach the emerald than any other green stones74 #c4 ,the demantoid garnet 7sometimes called olivine in the trade74 #d4 ,true olivine 7the peridot and the chrysolite of the trade74 #e4 ,bluish-green beryl 7aquamarine74 #f4 ,green sapphire 7,oriental emerald or ,oriental aquamarine74 #g4 ,chrysoberyl 7alexandrite and also the greenish-yellow chrysoberyl74 #a4 ,considering first the emerald1 we have as legitimate a use of color in distinguishing a stone as could be selected1 for emerald of fine grass-green color is not equaled by any other precious stone in the rich velvety character of its color4 ,we have to beware here1 however1 of the fine glass imitations1 which1 while lacking the variety of true emerald1 because of lack of dichroism1 are nevertheless of a color so nearly like that of the emerald that no one should attempt to decide by color alone as to whether a stone is genuine or imitation emerald4 ,if a hardness test shows that the material is a genuine hard stone and not a paste1 then one who is well accustomed to the color of fine emerald can say at once whether a stone is a fine emerald or some other hard green stone4 ,where the color is less fine1 however1 one might well refuse to decide by the color1 even when sure that the material is not glass1 for some fine tourmalines approach some of the poorer emeralds in richness of color4 ,,the ,,scientific ,,emerald ,,fraud4 ,no scientific emeralds of marketable size have ever been produced as far as can be learned4 ,many attempts to reproduce emerald by melting beryl or emerald of inferior color have resulted only in the production of a beryl glass1 which1 while its color might be of desirable shade1 was softer and lighter in weight than true emerald4 ,it was also a true glass and hence singly refracting and without dichroism1 whereas emerald is crystalline 7not glassy or amorphous71 is doubly refracting1 and shows dichroism4 ,do not be misled1 then1 into buying or selling an imitation of emerald under the terms synthetic1 scientific1 or reconstructed1 as such terms1 when so used1 are used to deceive one into thinking that the product offered bears the same relation to the true emerald that scientific rubies and sapphires bear to the natural stones4 ,such is not the case4 ,about the most dangerous imitation of the emerald that is ever seen in the trade is the triplet that has a top and a back made of true but pale beryl 7the same mineral as emerald1 but not of the right color7 and a thin slice of deep emerald green glass laid between4 ,this slice of glass is usually placed behind the girdle so that a file will not find any point of attack4 ,the specific gravity of the triplet is practically that of emerald1 its color is often very good1 and it is doubly refracting4 ,it is thus a dangerous imitation4 7,see ,fig4 #h47 ,,emerald ,,triplets4 ,a careful examination of one of these triplets1 in the unset condition1 with a good lens1 will reveal the thin line of junction of the beryl with the glass4 7,the surface lusters of the two materials are enough different for the trained eye to detect the margin at once47 ,such a triplet1 if held in the sun1 will reflect onto a card two images in pale or white light1 one coming from the top surface of the table and the other from the top surface of the glass slice within4 ,in other words1 it acts in this respect like a doublet4 ,a true emerald would give only one such reflection1 which would come from the top surface of the table4 ,illustration3 ,,fig4 #h4--;,,emerald ,,triplet4 #b4 ,tourmalines1 when green1 are usually darker than emeralds and of a more pronounced yellow green1 or they may be of too bluish a green1 as is the case with some of the finest of the green tourmalines from ,maine4 ,connecticut green tourmaline tends more to the dark yellowish green1 and ,ceylon tourmaline to the olive green4 ,the stronger dichroism of the tourmaline frequently reveals itself to the naked eye1 and there is usually one direction or position in which the color of the stone is very inferior to its color in the opposite direction or position4 ,most tourmalines 7except the very lightest shades7 must be cut so that the table of the finished stone lies on the side of the crystal1 as1 when cut with the table lying across the crystal 7perpendicular to the principal optical axis7 the stones are much too dark to be pretty4 ,hence when one turns the cut stone so that he is looking in the direction which was originally up and down the crystal 7the direction of single refraction and of no dichroism7 he gets a glimpse of a less lovely color than is furnished by the stone in other positions4 ,with a true emerald no such disparity in the color would appear4 ,there might be a slight change of shade 7as seen by the naked eye71 but no trace of an ugly shade would appear4 ,by studying many tourmalines and a few emeralds one may acquire an eye for the differences of color that characterize the two stones1 but it is still necessary to beware of the fine glass imitation and to use the file and also to look with a high-power glass for any rounding bubbles4 ,the emerald will never have the latter4 ,the glass imitation frequently does have them4 ,the sharp jagged flaws and cracks that so often appear in emerald are likely to appear also in tourmaline as both are brittle materials4 ,the glass imitations frequently have such flaws put into them either by pinching or by striking the material4 ,frequently1 too1 wisps of tiny air bubbles are left in the glass imitations in such fashion that unless one scrutinizes them carefully with a good lens they strongly resemble the flaws in natural emerald4 ,i have thus gone into detail as to how one may distinguish true emerald from tourmaline and from glass imitations because1 on account of the high value of fine emerald and its infrequent occurrence1 there is perhaps more need for the ability to discriminate between it and its imitations and substitutes than there is in almost any other case4 ,where values are high the temptation to devise and to sell imitations or substitutes is great and the need for skill in distinguishing between the real and the false is proportionally great4 #c4 ,the demantoid garnet 7often unfortunately and incorrectly called olivine in the trade7 is usually of an olive or pistachio shade4 ,it may1 however1 approach a pale emerald4 ,the refraction being single in this1 as in all garnets1 there is little variety to the color4 ,the dispersion being very high1 however1 there is a strong tendency1 in spite of the depth of the body color1 for this stone to display fire1 that is1 rainbow color effects4 ,the luster1 too1 is diamond-like as the name demantoid signifies4 ,with this account of the stone and a few chances to see the real demantoid garnet beside an emerald no one would be likely to mistake one for the other4 ,the demantoid garnet is also very soft as compared with emerald 7#f-a_/b as against nearly #h74 #d4 ,true olivine 7the peridot or the chrysolite of the trade7 is of a fine leaf-green or bottle-green shade in the peridot4 ,the chrysolite of the jeweler is usually of a yellower green4 ,frequently an olive-green shade is seen4 ,the luster of olivine 7whether of the peridot shade or not7 is oily1 and this may serve to distinguish it from tourmaline 7which it may resemble in color74 ,its double refraction is very large also1 so that the doubling of the edges of the rear facets may easily be seen through the table with a lens4 ,the dichroism is feeble too1 whereas that of tourmaline is strong4 ,no one would be likely to confuse the stone with true emerald after studying what has preceded4 #e4 ,bluish-green beryl 7aquamarine7 is usually of a pale transparent green or blue green 7almost a pure pale blue is also found74 ,having all the properties of its more valuable variety1 emerald1 the pale beryl may1 by the use of these properties1 be distinguished from the pale blue-green topaz which so strongly resembles it in color4 #f4 ,green sapphire seldom even approaches emerald in fineness of color4 ,when it remotely suggests emerald it is called ,oriental emerald to denote that it is a corundum gem4 ,most green sapphires are of too blue a green to resemble emerald4 ,some are really ,oriental aquamarines4 ,in some cases the green of the green sapphire is due to the presence1 within the cut stone1 of both blue and yellow portions1 the light from which1 being blended by its reflection within the stone1 emerges as green as seen by the unaided eye1 which cannot analyze colors4 ,the dark sapphires of ,australia are frequently green when cut in one direction and deep blue when cut in the opposite direction4 ,the green1 however1 is seldom pleasing4 #g4 ,chrysoberyl as usually seen is of a yellowish green4 ,the fine gem chrysoberyls known as alexandrites1 however1 have a pleasing bluish green or deep olive green color by daylight and change in a most surprising fashion by artificial light under which they show raspberry red tints4 ,this change1 according to ,g4 ,f4 ,herbert-,smith1 is due principally to the fact that the balance in the spectrum of light transmitted by the stone is so delicate that when a light1 rich in short wave lengths1 falls upon it the blue green effect is evident1 whereas when the light is rich in long wave lengths 7red end of the spectrum71 the whole stone appears red4 ,the strong dichroism of the species also aids this contrast4 ,the chrysoberyls of the cat's-eye type 7of fibrous or tubular internal structure7 are usually of olive green or brownish-green shades4 ,those who wish to further study color distinctions in green stones are recommended to see the chapters on beryl 7pp4 #ahd-aif71 peridot 7pp4 #bbe-bbg71 corundum 7pp4 #agb-ahc71 tourmaline 7pp4 #bai-bbd71 chrysoberyl 7pp4 #bcc-bcg71 and garnet 7demantoid1 pp4 #baf-bah7 in ,g4 ,f4 ,herbert-,smith's ,gem-,stones4 ,,lesson ,,xiii ,,color--,continued ,,blue ,,stones ,the species that furnish blue stones in sufficient number to deserve consideration are1 aside from opaque stones3 #a4 ,corundum 7sapphire74 #b4 ,spinel4 #c4 ,tourmaline4 #d4 ,topaz4 #e4 ,diamond4 #f4 ,zircon4 #a4 ,of these minerals the only species that furnishes a fine1 deep velvety blue stone is the corundum1 and fine specimens of the cornflower blue variety are very much in demand and command high prices4 ,the color in sapphires ranges from a pale watery blue through deeper shades 7often tinged with green7 to the rich velvety cornflower blue that is so much in demand1 and on to dark inky blues that seem almost black by artificial light4 ,most sapphires are better daylight stones than evening stones4 ,some of the sapphires from ,montana1 however1 are of a bright electric blue that is very striking and brilliant by artificial light4 ,,how ,,sapphires ,,should ,,be ,,cut4 ,the direction in which the stone is cut helps determine the quality of the blue color1 as the ordinary ray 7sapphire exhibits dichroism7 is yellowish and ugly in color1 and if allowed to be conspicuous in the cut stone1 its presence1 blending with the blue1 may give it an undesirable greenish cast4 ,sapphires should usually be cut so that the table of the finished stone is perpendicular to the principal optical axis of the crystal4 ,another way of expressing this fact is that the table should cross the long axis of the usual hexagonal crystal of sapphire1 at right angles4 ,this scheme of cutting puts the direction of single refraction up and down the finished stone1 and leaves the ugly ordinary rays in poor position to emerge as the light that falls upon the girdle edges cannot enter and cross the stone to any extent4 ,to find out with a finished stone whether or not the lapidary has cut it properly as regards its optical properties one may use the dichroscope1 and if there is little or no dichroism in evidence when looking through the table of the stone it is properly cut4 ,where a sapphire shows a poor color and the dichroscope shows that the table was laid improperly1 there is some possibility of improving the color by recutting to the above indicated position4 ,however1 one must use much judgment in such a case1 as sapphires1 like other corundum gems1 frequently have their color irregularly distributed1 and the skillful lapidary will place the culet of the stone in a bit of good color1 and thus make the whole stone appear to better advantage4 ,it would not do to alter such an arrangement1 as one would get poorer rather than better color by recutting in such a case4 ,while some of the blue stones about to be described may resemble inferior sapphires1 none of them approaches the better grades of sapphire in fineness of blue coloration4 ,the scientific sapphire1 of course1 does approach and even equals the natural sapphire so that one must know how to distinguish between them4 ,this distinction is not one of color1 however1 and it will be separately considered a little later4 #b4 ,blue spinels are infrequently seen in commerce4 ,they never equal the fine sapphire in their color1 being more steely4 ,they1 of course1 lack dichroism and are softer than sapphire as well as lighter4 #c4 ,blue tourmalines are never of fine sapphire blue4 ,the name indicolite which mineralogists give to these blue stones suggests the indigo-blue color which they afford4 ,the marked dichroism of tourmaline will also help detect it4 ,some tourmalines from ,brazil are of a lighter shade of blue and are sometimes called ,brazilian sapphires4 #d4 ,blue topaz is usually of a pale sky blue or greenish blue and is likely to be confused with beryl of similar color4 ,the high density of topaz 7#c4ec7 as compared with beryl 7#b4gd7 serves best to distinguish it4 ,,fancy ,,blue ,,diamonds4 #e4 ,blue diamonds are usually of very pale bluish or violet tint4 ,a few deeper blue stones are seen occasionally as fancy diamonds4 ,these are seldom as deep blue as pale sapphires4 ,even the famous ,hope ,blue ,diamond1 a stone of about forty-four carats and of great value1 is said to be too light in color to be considered a fine sapphire blue4 ,some of the deeper blue diamonds have a steely cast4 ,the so-called blue-white stones are rarely blue in their body color1 but rather are so nearly white that the blue parts of the spectra which they produce are very much in evidence1 thus causing them to face up blue4 ,there is little likelihood of mistaking a bluish diamond for any other stone on account of the fire and the adamantine luster of the diamond4 #f4 ,blue zircon1 however1 has nearly adamantine luster and considerable fire4 ,the color is usually sky blue4 ,such stones are seldom met with in the trade4 ,for a more detailed account of the various blue stones see ,g4 ,f4 ,herbert-,smith's ,gem-,stones1 as follows3 ,for sapphires1 pp4 #agb-agc1 #agf1 #ahb2 for spinel1 pp4 #bjc1 #bjd1 #bje2 for tourmaline1 pp4 #bbj1 #bba1 #bbc2 for topaz1 pp4 #aih1 #bjj1 #bja2 for diamond1 pp4 #acj1 #acf1 #agj1 and for zircon1 pp4 #bbi1 #bca4 ,,lesson ,,xiv ,,color--,concluded ,,pink1 ,,purple1 ,,brown1 ,,and ,,colorless ,,stones ,,pink ,,stones4 ,pink stones are yielded by 7#a7 corundum 7pink sapphire71 7#b7 spinel 7balas ruby71 7#c7 tourmaline 7rubellite71 7#d7 true topaz 7almost always artificially altered71 7#e7 beryl 7morganite71 7#f7 spodumene 7kunzite71 and 7#g7 quartz 7rose-quartz74 ,these pink minerals are not easily differentiated by color alone1 as the depth and quality of the pink vary greatly in different specimens of the same mineral and in the different minerals4 ,there is dichroism in the cases of pink sapphire1 pink tourmaline 7strong71 pink topaz 7strong71 pink beryl 7less pronounced71 and kunzite 7very marked and with a yellowish tint in some directions that contrasts with the beautiful violet tint in another direction in the crystal74 ,pink quartz is almost always milky1 and shows little dichroism4 ,pink spinel is without dichroism1 being singly refracting4 ,hardness and specific gravity tests will best serve to distinguish pink stones from each other4 ,the color alone is not a safe guide4 ,,purple ,,stones4 ,among the mineral species that furnish purple stones1 7#a7 quartz is pre-eminent in the fineness of the purple color4 ,such purple stones are1 of course1 known as amethysts4 ,after quartz come 7#b7 corundum 7,oriental amethyst71 7#c7 spinel 7almandine spinel71 7#d7 garnet 7almandine71 and 7#e7 spodumene 7variety kunzite74 ,the purple of the amethyst varies from the palest tints to the full rich velvety grape-purple of the so-called ,siberian amethysts4 ,the latter are of a reddish purple 7sometimes almost red7 by artificial light1 but of a fine violet by daylight4 ,no other purple stone approaches them in fineness of coloring1 so that here we have a real distinction based on color alone4 ,if the purple is paler1 however1 one cannot be sure of the mineral by its color4 ,purple corundum 7,oriental amethyst7 is seldom as fine in color as ordinary amethyst1 and never as fine as the best amethyst4 ,it is usually of a redder purple1 and by artificial light is almost ruby-like in its color4 ,purple spinels are singly refracting1 and lack dichroism1 and hence lack variety of color4 ,almandine garnets also show no dichroism and lack variety of color4 ,the garnets are1 as a rule1 apt to be more dense in color than the spinels4 ,purple spodumene 7kunzite7 is pinkish to lilac in shade--usually pale1 unless in large masses1 and it shows very marked dichroism4 ,a yellowish cast of color may be seen in certain directions in it also1 which will aid in distinguishing it from other purple stones4 ,,brown ,,stones4 7#a7 ,diamond1 7#b7 garnet1 7#c7 tourmaline1 and 7#d7 zircon furnish the principal brown stones4 ,diamond1 when brown1 unless of a deep and pleasing color1 is very undesirable1 as it absorbs much light1 and appears dirty by daylight and dark and sleepy by artificial light4 ,when of a fine golden brown a diamond may have considerable value as a fancy stone4 ,such golden fancies can be distinguished from other brown stones 7except perhaps brown zircons7 by their adamantine luster1 and their prismatic play or fire4 ,brown garnet 7hessonite or cinnamon stone71 sometimes wrongly called hyacinth in the trade1 is of a deep reddish-brown color4 ,usually the interior structure1 as seen under a lens1 is streaky1 having a sort of mixed oil and water appearance4 ,brown tourmaline is sometimes very pleasing in color4 ,it is deep in shade1 less red than cinnamon stone1 and with marked dichroism1 which both brown diamond and brown garnet lack4 ,brown zircon1 while lacking dichroism1 is frequently rich and pleasing in shade1 and when well cut is very snappy1 the luster being almost adamantine1 the dispersion being large1 and the refractive index high4 ,it is useless to deny that by the unaided eye one might be deceived into thinking that a fine brown zircon was a brown diamond4 ,however1 the large double refraction of the zircon easily distinguishes it from diamond 7use the sunlight-card method or look for the doubling of the edges of the rear facets as seen through the table74 ,the relative softness 7#g-a_/b7 also easily differentiates it from diamond4 ,,colorless ,,stones4 ,few colorless stones other than diamond1 white sapphire 7chiefly scientific71 and quartz are seen in the trade4 ,colorless true topaz is sometimes sold and artificially whitened zircon 7jargoon7 is also occasionally met with4 ,beryl of very light green tint or even entirely colorless may also be seen at times4 ,such colorless stones must of course be distinguished by properties other than color4 ,they are mentioned here merely that the learner may be aware of what varieties of gem minerals occur in the colorless condition1 and that all these minerals also occur with color in their more usual forms4 ,this does not even except the diamond1 which is rarely truly colorless4 ,,lesson ,,xv ,,how ,,to ,,tell ,,scientific ,,stones ,,from ,,natural ,,gems ,it should be said first that the only true scientific or synthetic stones on the market are those having the composition and properties of corundum1 that is to say1 the ruby and the several color varieties of sapphire1 as blue1 pink1 yellow1 and white4 ,there is also a greenish stone that appears reddish by artificial light1 which is called scientific alexandrite but which has1 however1 the composition and properties of the corundum gems rather than those of true alexandrite4 ,all so-called scientific emeralds have proved to be either of paste of one sort or another1 or else triplets having a top and a back of some inexpensive but hard stone of pale color1 and a central slice of deep green glass1 the three pieces being cemented together so skillfully that the junctions frequently escape any but a very careful examination with a lens4 ,,all ,,scientific ,,stones ,,are ,,corundum ,,gems4 ,now the fact that all true scientific stones are corundum gems makes their determination fairly simple on the following basis3 ,among the considerable number of corundum gems of nature1 whether ruby or sapphire of various colors1 there is seldom found one that is entirely free from defects4 ,almost always1 even in what are regarded as fine specimens1 one will easily find with a glass1 defects in the crystallization4 ,moreover these defects are characteristic of the corundum gems4 ,the scientific corundum gems1 however1 never have these specific defects4 ,hence the surest and simplest way of distinguishing between the two kinds of stones is to acquaint oneself with the typical defects of natural corundum gems1 and then to look for such defects in any specimen of ruby or sapphire that is in question4 ,while a description of some of the most common of the typical defects of rubies and sapphires is to follow1 the jeweler1 who may not yet be familiar with them by actual experience1 owes it to himself and to his customers to acquaint himself at first hand with the natural defects of such material1 which he is always in a position to do through the courtesy of representatives of houses dealing in precious stones1 if he himself does not carry such material in stock4 ,,typical ,,defects ,,of ,,natural ,,corundum ,,gems4 ,perhaps the most common of the defects of natural corundum gems is the peculiar appearance known as silk4 ,this is best seen when a strong light is allowed to stream through the stone at right angles to the observer's line of sight4 ,sets of fine1 straight1 parallel lines will be seen1 and these will frequently meet other sets of similar lines at an angle of #abj degrees 7like the angle at which the sides of a regular hexagon meet7 or the lines may cross each other at that angle or at an angle of #fj degrees 7the supplement of #abj degrees74 ,such straight parallel lines are never seen in scientific stones1 and their presence may be taken to indicate positively that the stone having them is a natural stone4 ,in fine specimens of natural ruby or sapphire such lines will be few and difficult to find1 but in some position or other they will usually be found if the search is even as careful as that which one would habitually employ in looking for defects in a diamond4 ,in the vast majority of cases no such careful search will be required to locate silk in natural rubies1 and if a stone that is apparently a ruby is free from such defects it is almost a foregone conclusion it is a scientific stone4 ,another common type of defect in corundum gems is the occurrence of patches of milky cloudiness within the material4 ,a little actual acquaintance with the appearance of this sort of defect in natural stones will make it easy to distinguish from the occasional cloudiness found in scientific stones1 which latter cloudiness is due to the presence of swarms of minute gas bubbles4 ,these tiny bubbles can be seen under a high power lens1 and this suggests a third feature that may be used to tell whether one has a natural stone or not4 ,natural rubies and sapphires1 like scientific ones1 frequently contain bubbles1 but these are always angular in the natural stones1 while those of the scientific stones are generally round or rounding1 never angular4 ,to sum up the suggestions already presented it may be said that1 since natural and scientific corundum gems are composed of essentially the same material1 and have identically the same physical and chemical properties1 and frequently very closely resemble each other in color1 it is necessary to have recourse to some other means of distinguishing between them4 ,the best and simplest means for those who are acquainted with the structural defects common to natural corundum gems is to seek for such defects in any specimen that is in question1 and if no such defects can be found1 to be very sceptical as to the naturalness of the specimen1 inasmuch as perfect corundum gems are very rare in nature1 and when of fine color command exceedingly high prices4 ,no jeweler can afford to risk his reputation for knowledge and for integrity by selling as a natural stone any gem which does not possess the minor defects common to practically all corundum gems4 ,,structural ,,defects ,,of ,,scientific ,,stones4 ,so far our tests have been mostly negative4 ,it was said1 however1 that spherical bubbles sometimes appear in scientific gems4 ,another characteristic structural defect of practically every scientific gem may be utilized to distinguish them4 ,as is well known1 the rough material is formed in boules or pear-shaped drops under an inverted blowpipe4 ,the powdered material is fed in with one of the gases and passes through the flame1 melting as it goes1 and then accumulating and crystallizing below as a boule4 ,the top or head of this boule is rounding from the start1 and hence the successive layers of material gather in thin curved zones4 ,the color and structure of these successive zones are not perfectly uniform1 hence when cut stones are made from the boules these curving parallel layers may be seen within by the use of a good lens1 especially if the cut stone is held in a strong crossing light1 as was suggested when directions were given above as to the best way to look for silk in a natural stone4 ,owing to the shape of a well cut stone it is sometimes difficult to get light through the material1 yet by turning the stone repeatedly1 some position will be found in which the curving parallel stri can be seen4 ,they are easily seen in scientific ruby1 less easily in dark blue sapphire1 but still they can be found on close search4 ,in the light colored stones and in white sapphire1 the difficulty is greater1 as there are no color variations in the latter case4 ,however1 the value of white sapphire is so slight1 whether natural or artificial1 that it is a matter of but little moment1 and what has already been said as to natural defects1 applies to white sapphire as well as to the colored varieties1 and absolutely clear and perfect natural white sapphire is rare4 ,one more distinguishing mark of the scientific stones may be added to give full measure to the scheme of separation1 that no one need be deceived4 ,the surface finish of the scientific stones is rarely as good as that of the natural material and it appears to be more difficult to produce a good polish on scientific stones than on natural ones4 ,the degree of hardness of the scientific stones seems to be slightly variable in different parts of the same piece so that the polishing material removes the surface material unequally1 leaving minute streaky marks on the surfaces of the facets4 ,possibly this condition might be remedied by skillful treatment1 but hardly at the price obtainable for the product1 so that a close study of the surface finish will sometimes help in distinguishing between natural and artificial material4 ,any fine specimen of natural ruby or sapphire will have usually received very expert treatment and a splendid surface finish4 ,in conclusion1 then1 the points to be remembered in determining the origin of corundum gems are four in number4 #a4 ,expect to find natural defects1 such as silk or cloudy patches1 or angular bubbles in all natural stones4 #b4 ,if bubbles are present in artificial material they will be round or rounding4 #c4 ,artificial material will always have curving parallel stri within it4 #d4 ,the surface finish of artificial material is seldom or never equal to that of natural material4 ,it ought not to be necessary to add that material from either source may be cut to any shape1 and that artificial rubies may be seen in most ,oriental garb1 hence all specimens should have applied to them the above tests regardless of the seeming antiquity of their cut or of their alleged pedigree4 ,,lesson ,,xvi ,,how ,,to ,,test ,,an ,,unknown ,,gem ,having now considered separately the principal physical properties by means of which one can identify a precious stone1 let us attempt to give as good an idea as the printed page can convey of how one should go about determining to what species a gem belongs4 ,,signs ,,of ,,wear ,,in ,,an ,,emerald4 ,to make the matter more concrete1 and therefore more interesting1 let us consider a real case1 the most recent problem1 in fact1 that the author has had to solve4 ,a lady of some wealth had purchased1 for a large sum1 a green stone which purported to be an emerald4 ,after a few years of wear as a ring stone she noticed one day that the stone had dulled around the edges of its table1 and thinking that that ought not to be the case with a real emerald1 she appealed to a dealer in diamonds to know if her stone was a real emerald4 ,the diamond merchant told her frankly that1 while he was competent in all matters pertaining to diamonds1 he could not be sure of himself regarding colored stones1 and advised the lady to see the author4 ,the matter being thus introduced1 the lady was at once informed that even a real emerald might show signs of wear after a few years of the hard use that comes to a ring stone4 ,while emerald has1 as we saw in the lesson on hardness1 a degree of hardness rated as nearly #h 7#g-a_/b in the table71 it is nevertheless a rather brittle material and the long series of tiny blows that a ring stone is bound to meet with will cause minute yielding along the exposed edges and corners of the top facets4 ,this being announced1 the first step in the examination of the stone was to clean it and to give it a careful examination with a ten-power lens4 7,an aplanatic triplet will be found best for this purpose47 ,,color4 ,the color was1 of course1 the most obvious property1 but1 as has already been said1 color is not to be relied upon in all cases4 ,in this case the color was a good emerald green but a bit bluer than the finest grass green4 ,a very fine ,maine tourmaline might approach this stone in color1 so it became necessary to consider this possibility4 ,a glass imitation1 too1 might have a color equal or superior to this4 ,,imperfections4 ,while noting the color1 the imperfections of the stone claimed attention4 ,they consisted mainly of minute jagged cracks of the character peculiar to brittle materials such as both emerald and tourmaline4 ,so far it will be noted either of the above minerals might have furnished the lady's gem4 ,as glass can be artificially crackled to produce similar flaws the stone might have been only an imitation as far as anything yet learned about it goes4 ,,file ,,test4 ,the next step was to test its hardness by gently applying a very fine file to an exposed point at one corner of the girdle4 ,the file slipped on the material as a skate slips on ice4 ,evidently we did not have to do with a glass imitation4 ,,refraction4 ,knowing now that we had a true hard mineral1 it remained to be determined what mineral it was4 ,on holding the stone in direct sunlight and reflecting the light onto a white card it was seen at once that the material was doubly refracting1 for a series of double images of the back facets appeared4 ,these double images might have been produced by tourmaline as well as by emerald4 7,not however by glass which is singly refracting47 ,if a direct reading refractometer had been available the matter could have been settled at once by reading the refractive indices of the material1 for tourmaline and emerald have not only different refractive indices but have double refraction to different degrees4 ,such an instrument was not available at the time and will hardly be available to most of those who are studying this lesson1 so we can go on with our account of the further testing of the green stone4 ,,hardness4 ,a test upon the surface of a quartz crystal showed that the stone was harder than quartz 7but so is tourmaline74 ,a true topaz crystal was too hard for the ring stone1 whose edge slipped over the smooth topaz surface4 ,the green stone was therefore not a green corundum 7,oriental emerald7 as the latter has hardness #i and scratches topaz4 ,with hardness evidently between #g and #h and with double refraction and with the kind of flaws peculiar to rather brittle minerals we had in all probability either a tourmaline or an emerald4 ,,dichroism4 ,the dichroscope 7which might have been used much earlier in the test but was not at hand at the time7 was next tried and the stone was seen to have marked dichroism--a bluish green and a yellowish green appearing in the two squares of the instrument when the stone was held in front of the opening and viewed against a strong light4 ,as either tourmaline or emerald might thus exhibit dichroism 7the tourmaline more strongly1 however1 than the emerald7 one more test was tried to finally decide the matter4 ,,specific ,,gravity4 ,the stone was removed from its setting and two specific gravity determinations made by means of a specific gravity bottle and a fine chemical balance4 ,the two results1 which came closely alike1 averaged #b4gj which agrees very nearly with emerald 7#b4gd7 and which is far removed from the specific gravity of tourmaline 7#c4aj74 ,the stone was now definitely known to be an emerald1 as each of several tests agreed with the properties of emerald1 namely3 ,color--nearly grass green4 ,imperfections--like those of emerald4 ,hardness--#g-a_/b4 ,refraction--double4 ,dichroism--easily noted4 ,specific gravity--#b4gj4 ,while one who was accustomed to deal in fine emeralds might not need to make as detailed an examination of the stone as has just been indicated above1 yet for most of us who do not have many opportunities of studying valuable emeralds it is safer to make sure by complete tests4 ,one other concrete example of how to go about testing unknown stones must suffice to conclude this lesson1 after which the student1 who has mastered the separate lessons preceding this1 should proceed to test as many unknowns as his time and industry permit in order to really make his own the matter of these lessons4 ,it may be added here that the task of testing a stone is much more rapid than this laborious effort to teach others how to do it might indicate4 ,to one skilled in these matters only a few seconds are required for the inspection of a stone with the lens1 the dichroscope1 or the refractometer1 and hardness tests are swiftly made4 ,a specific gravity test requires more time and should be resorted to only when there remains a reasonable doubt after other tests have been applied4 ,now for our final example4 ,a red stone1 cut in the form of a pear-shaped brilliant1 was submitted to the writer for determination4 ,it had been acquired by an ,american gentleman in ,japan from an ,east ,indian who was in financial straits4 ,along with it1 as security for a loan1 the ,american obtained a number of smaller red stones1 a bluish stone1 and a larger red stone4 ,the red stones were all supposed to be rubies4 ,on examination of the larger red stone with a lens it was at once noted that the internal structure was that of scientific ruby4 ,,testing ,,other ,,stones4 ,somewhat dashed by the announcement of this discovery the owner began to fear that all his gems were false4 ,examination of the small red stones showed abundance of silk1 a peculiar fibrous appearance within the stone caused by its internal structure4 ,the fibers were straight and parallel1 not curved and parallel as in synthetic ruby4 ,tiny bubbles of angular shape also indicated that the small stones were natural rubies4 ,they exhibited dichroism and scratched topaz and it was therefore decided that they at least were genuine4 ,the pear-shaped brilliant which was first mentioned was of a peculiar1 slightly yellowish1 red color4 ,it was very pellucid and free from any stri either of the straight or curved types4 ,it had in fact no flaws except a rather large nick on one of the back surfaces near the girdle4 ,this was not in evidence from the front of the stone and had evidently been left by the ,oriental gem cutter to avoid loss in weight while cutting the stone4 ,the peculiar yellowish character of the red color led us to suspect ruby spinel4 ,the stone was therefore inspected with the dichroscope and found to possess no dichroism4 ,the sunlight-card test1 too1 showed that the stone was singly refracting4 ,a test of the hardness showed that the material barely scratched topaz1 but was attacked by sapphire4 ,it was therefore judged to be a red spinel4 ,the large bluish stone which the gentleman acquired with the red stones proved to be iolite1 sometimes called cordierite or water-sapphire 7,saphir d'eau71 a stone seldom seen in this country4 ,it had marked dichroism--showing a smoky blue color in one direction and a yellowish white in another4 ,the difference was so marked as to be easily seen without the dichroscope4 ,,lesson ,,xvii ,,suitability ,,of ,,stones ,,for ,,various ,,types ,,of ,,jewels1 ,,as ,,determined ,,by ,,hardness1 ,,brittleness1 ,,and ,,cleavability ,,hard ,,stones ,,not ,,necessarily ,,tough4 ,as was suggested in the lesson on hardness there is prevalent in the public mind an erroneous belief that hardness carries with it ability to resist blows as well as abrasion4 ,now that it does not follow that because a precious stone is very hard1 it will wear well1 should be made plain4 ,some rather hard minerals are seldom or never used as gems1 in spite of considerable beauty and hardness1 because of their great brittleness4 ,other stones1 while fairly hard and reasonably tough in certain directions1 have nevertheless so pronounced a cleavage that they do not wear well if cut1 and are sometimes very difficult to cut at all4 ,in view of these facts it will be well to consider briefly what stones1 among those most in use1 are sufficiently tough as well as hard1 to give good service in jewels1 such as rings1 which are subject to rough wear4 ,we may also consider those stones1 whose softness1 or brittleness1 or ready cleavability1 requires that they should be reserved for use only in those jewels which1 because of their nature1 receive less rough usage4 ,in order to deal with the principal gems systematically1 let us consider them in the order of their hardness1 beginning with the hardest gem material known1 which is1 of course1 diamond4 ,,durability ,,of ,,the ,,diamond4 ,fortunately this king of gems possesses in addition to its great hardness1 considerable toughness1 and although it is readily cleavable in certain directions it nevertheless requires a notable amount of force applied in a particular direction to cause it to cleave4 ,although sharp knocks will occasionally flake off thin layers from diamonds when roughly worn in rings1 or even in extreme cases fracture them1 yet this happens but seldom and1 as the enormous use of the diamond in ring mountings proves1 it is entirely suitable for that purpose4 ,it follows that1 if a stone can stand ring usage1 it can safely be used for any purpose for which precious stones are mounted4 ,,the ,,corundum ,,gems4 ,next after the diamond in hardness come the corundum gems1 i4 e41 ruby1 sapphire1 and the series of corundum gems of colors other than red and blue4 ,these stones have no noticeable cleavage and are exceedingly tough1 for minerals1 as well as very hard4 ,we have only to consider the use of impure corundum 7emery7 as a commercial abrasive in emery wheels1 emery cloth1 emery paper1 etc41 to see that the material is tough4 ,any of the corundum gems therefore may be used in any type of jewel without undue risk of wear or breakage4 ,customers of jewelers should1 however1 be cautioned against wearing ruby or sapphire rings on the same finger with a diamond ring in cases where it would be possible for the two stones to rub against each other4 ,so much harder than the ruby is the diamond 7in spite of the seeming closeness of position in ,mohs's scale7 that the slightest touch upon a ruby surface with a diamond will produce a pronounced scratch4 ,the possessor of diamonds and other stones should also be cautioned against keeping them loose in the same jewel case or other container1 as the shaking together may result in the scratching of the softer materials4 ,the ,arabs are said to have a legend to the effect that the diamond is an angry stone and that it should not be allowed to associate with other stones lest it scratch them4 ,,chrysoberyl4 ,passing on to the next mineral in the scale of hardness we come to chrysoberyl1 which is rated as #h-a_/b on ,mohs's scale4 ,this mineral furnishes us the gem1 alexandrite1 which is notable for its power to change in color from green in daylight to red in artificial light4 ,chrysoberyl also supplies the finest cat's-eyes 7when the material is of a sufficiently fibrous or tubular structure71 and it further supplies the greenish-yellow stones frequently 7though incorrectly7 called chrysolite by jewelers4 ,the material is very hard and reasonably tough and may be used in almost any suitable mounting4 ,,spinel4 ,after chrysoberyl come the materials rated as about #h in hardness4 ,first and hardest of these is spinel1 then comes true or precious topaz4 ,the various spinels are very hard and tough stones4 ,the rough material persists in turbulent mountain streams where weaker minerals are ground to powder1 and when cut and polished1 spinel will wear well in any jewel4 ,the author has long worn a ruby spinel in a ring on the right hand and has done many things that have subjected it to hard knocks1 yet it is still intact1 except for a spot that accidentally came in contact with a fast-flying carborundum wheel1 which of course abraded the spinel4 ,,topaz4 ,the true topaz is a bit softer than spinel1 and the rough crystals show a very perfect basal cleavage4 ,that is1 they will cleave in a plane parallel to the bases of the usual orthorhombic crystals4 ,this being the case a cut topaz is very likely to be damaged by a blow or even by being dropped on a hard surface1 and it would be wiser not to set such a stone in a ring unless it was to be but little used1 or used by one who would not engage in rough work while wearing it4 ,thus a lady might wear a topaz ring on dress occasions for a long time without damaging it1 but it would not do for a machinist to wear one in a ring4 ,,gems ,,between #g ,,and #h ,,in ,,hardness4 ,we now come to a rather long list of gem minerals ranging between #g and #h in hardness4 ,of these the principal ones are zircon1 almandine garnet1 and beryl 7emerald and aquamarine7 rated as #g-a_/b in hardness1 and pyrope and hessonite garnet rated as #g-a_/d in hardness4 ,tourmaline and kunzite may also be included in this group as being on the average slightly above #g in hardness4 ,the above minerals are all harder than quartz1 and hence not subject to abrasion by the quartz dust which is everywhere present4 ,in this respect they are suitable for fairly hard wear4 ,the garnets are of sufficient toughness so that they may be freely used in rings--and the extensive use of thin slices of garnet to top doublets proves the suitability of the material for resisting wear4 ,the zircon is rather more brittle and the artificially whitened zircons 7known as jargoons7 are especially subject to breakage when worn in rings4 ,fortunately jargoons are not commonly sold4 ,the beryl1 whether emerald or aquamarine1 is rather brittle4 ,emeralds are seldom found in river gravels4 ,the material cannot persist in the mountain streams that bring down other and tougher minerals4 ,the extreme beauty and value of the emerald has led to its use in the finest jewels1 and the temptation is strong to set it in rings1 especially in rings for ladies4 ,if such rings are worn with the care that valuable jewels should receive they will probably last a long time without any more serious damage than the dulling of the sharp edges of the facets around the table4 ,this slight damage can at any time be repaired by a light repolishing of the affected facets4 ,if an emerald is already badly shattered1 or as it is called mossy in character1 it will not be wise to set it in a ring1 as a slight shock might complete its fracture4 ,what has been said about emerald applies equally to aquamarine except that the value at stake is much less and the material is usually much freer from cracks4 ,tourmalines1 like emeralds1 are brittle1 and should be treated accordingly4 ,here1 however1 we are dealing with a much less expensive material than emerald1 and if a customer desires a tourmaline in a ring mounting1 while it will be best to suggest care in wearing it1 the loss1 in case of breakage1 will usually be slight4 ,kunzite1 like all spodumene1 has a pronounced cleavage4 ,it should therefore be used in brooches1 pendants1 and such jewels1 rather than in rings4 ,lapidaries dislike to cut it under some conditions because of its fragility4 ,,quartz ,,gems4 ,coming down to hardness #g we have the various quartz gems and jade 7variety jadeite74 ,the principal quartz gems are1 of course1 amethyst and citrine quartz 7the stone that is almost universally called topaz in the trade74 ,as crystalline quartz is fairly tough and lacks any pronounced cleavage1 and as it is as hard as anything it is likely to meet with in use1 it is a durable stone in rings or in other mountings4 ,in the course of time the sharp edges will wear dull from friction with objects carrying common dust1 which is largely composed of powdered quartz itself1 and which therefore gradually dulls a quartz gem4 ,old amethysts or topazes that have been long in use in rings show this dulling4 ,there is1 however1 little danger of fracture with amethyst or topaz unless the blow is severe and then any stone might yield4 ,the many semi-precious stones which have a quartz basis 7such as the varieties of waxy or cryptocrystalline chalcedony which is largely quartz in a very minutely crystalline condition7 are often even tougher than the clear crystallized quartz4 ,carnelian1 agate1 quartz cat's-eye1 jasper 7containing earthy impurities71 and those materials in which quartz has more or less completely replaced other substances1 such as silicified crocidolite1 petrified wood1 chrysocolla quartz1 etc41 are all nearly as hard and quite as tough as quartz itself1 and they make admirable stones for inexpensive rings of the arts and crafts type4 ,,jade4 ,jade1 of the jadeite variety1 which is rarer than the nephrite jade1 and more highly regarded by the ,chinese1 is an exceedingly tough material4 ,one can beat a chunk of the rough material with a hammer without making much impression upon it4 ,it is also fairly hard1 about as hard as quartz1 and with the two properties of toughness and hardness it possesses excellent wearing qualities in any kind of mounting4 ,true jade1 whether jadeite or nephrite1 deserves a larger use in inexpensive ornaments1 as it may be had of very fine green color and it is inexpensive and durable4 ,,softer ,,stones4 ,coming next to those minerals whose hardness is #f or over1 but less than #g1 we have to consider jade of the nephrite variety1 demantoid garnet 7olivine of the trade71 peridot 7or chrysolite1 or the olivine of the mineralogist71 turquoise1 moonstone1 and opal4 ,as has already been said of jadeite1 the jade of the nephrite variety1 while slightly less hard1 is about as tough a mineral as one could expect to find4 ,it can take care of itself in any situation4 ,the demantoid garnet 7the olivine of the trade7 is so beautiful and brilliant a stone that it is a pity that it is so lacking in hardness4 ,it will do very well for mounting in such jewels as scarf pins1 lavallires1 etc41 where but little hard wear is met with1 but it cannot be recommended for hard ring use4 ,the peridot1 too1 is rather soft for ring use and will last much better in scarf pins or other mountings little subject to rubbing or to shocks4 ,turquoise1 although rather soft1 is fairly tough1 as its waxy luster might make one suppose1 and in addition1 being an opaque stone1 slight dulling or scratching hardly lessens its beauty4 ,it may therefore be used in ring mountings4 ,however1 it should be suggested that most turquoise is sufficiently porous to absorb grease1 oil1 or other liquids1 and its color is frequently ruined thereby4 ,of course1 such a change is far more likely to occur to a ring stone than to a turquoise mounted in some more protected situation4 ,the moonstone1 being a variety of feldspar1 has the pronounced cleavage of that mineral and will not stand blows without exhibiting this property4 ,moonstones are therefore better suited to the less rude service in brooch mountings1 etc41 than to that of ring stones4 ,however1 being comparatively inexpensive1 many moonstones1 especially of the choicer bluish type1 are set in ring mountings4 ,the lack of hardness may be expected to dull their surfaces in time even though no shock starts a cleavage4 ,,the ,,opal4 ,there remains the opal1 of hardness #f1 to be considered4 ,as is well known opal is a solidified jelly of siliceous composition1 containing also combined water4 ,it is not only soft but very brittle and it will crack very easily4 ,many opals crack in the paper in which they are sold1 perhaps because of unequal expansion or contraction1 due to heat or cold4 ,in spite of this fragility1 thousands of fine opals1 and a host of commoner ones1 are set in rings1 where many of them subsequently come to a violent end1 and all1 sooner or later1 become dulled and require repolishing4 ,the great beauty of the opal1 rivaling any mineral in its color-play1 causes us to chance the risk of damage in order to mount it where its vivid hues may be advantageously viewed by the wearer as well as by others4 ,,very ,,soft ,,stones4 ,of stones softer than #f we have but few and none of them is really fit for hard service4 ,lapis lazuli1 #e-a_/b in hardness1 has a beautiful blue color1 frequently flecked with white or with bits of fool's gold4 ,its surface soon becomes dulled by hard wear4 ,two more of the softer materials1 malachite and azurite1 remain to be described4 ,these are both varieties of copper carbonate with combined water1 the azurite having less water4 ,both take a good polish1 but fail to retain it in use1 being only of hardness #c-a_/b to #d4 ,,lesson ,,xviii ,,mineral ,,species ,,to ,,which ,,the ,,various ,,gems ,,belong ,,and ,,the ,,chemical ,,composition ,,thereof ,although we have a very large number of different kinds of precious and semi-precious stones1 to judge by the long list of names to be found in books on gems1 yet all these stones can be rather simply classified on the basis of their chemical composition1 into one or another of a comparatively small number of mineral species4 ,while jewelers seldom make use of a knowledge of the chemistry of the precious stones in identifying them1 nevertheless such a knowledge is useful1 both by way of information1 and because it leads to a better and clearer understanding of the many similarities among stones whose color might lead one to regard them as dissimilar4 ,,mineral ,,species4 ,we must first consider what is meant by a mineral species and find out what relation exists between that subject and chemical composition4 ,now by a mineral species is understood a single substance1 having 7except for mechanically admixed impurities7 practically a constant chemical composition1 and having practically identical physical properties in all specimens of it4 ,,diamond ,,and ,,corundum4 ,a chemist would call a true mineral a pure substance1 just as sugar and salt are pure substances to the chemist4 ,thus diamond is a mineral species1 as is also corundum4 ,there are many different colors of both diamond and corundum1 but these different colors are believed to be due to the presence in the pure substance of impurities in small amounts4 ,thus every diamond consists mainly of pure carbon1 and all the corundum gems 7ruby and the various colors of sapphire7 consist mainly of pure oxide of aluminum4 ,the properties of all diamonds are practically alike and so are the properties of all the corundum gems whether red 7ruby71 blue 7sapphire71 yellow 7,oriental topaz71 green 7,oriental emerald71 or purple 7,oriental amethyst74 ,thus all diamonds1 of whatever color1 belong to the one species1 diamond1 and in this case the usual custom in naming them agrees with the facts4 ,similarly all sapphires1 of whatever color1 belong to the mineral species corundum4 ,thus a ruby is a red corundum4 ,the old ,french traveler and gem merchant1 ,tavernier1 tells us that in the seventeenth century1 when he visited the mines of ,pegu1 the natives knew of the similarity of the corundum gems and even called all by one name1 with other names attached to designate the color4 ,singularly enough1 the common name used by them was ruby rather than sapphire1 as now4 ,thus they called blue corundum gems blue rubies2 yellow corundums1 yellow rubies1 etc4 ,it is easily seen that if one recognizes the similar nature of all the many colors and shades of corundum that the number of things that one has to remember in order to be well acquainted with these stones is considerably diminished4 ,thus1 instead of having a whole series of specific gravities to remember one has only to remember that all the corundum gems have a specific gravity of approximately #d4 ,similarly they are all of practically the same refractive index 7#a4gfa-a4ggj1 being doubly refracting7 that they all exhibit dichroism when at all deeply colored1 etc4 ,having thus indicated what we mean by mineral species and having illustrated the matter by the cases of diamond and corundum and further having stated that all diamonds are composed of pure carbon 7except for traces of impurities7 and all corundum gems mainly of oxide of aluminum1 we may proceed to consider other mineral species and find out what gems they afford us4 ,,carbon1 ,,the ,,only ,,element ,,furnishing ,a ,,gem4 ,it will be noted that the first species considered1 diamond1 consisted of but a single element1 carbon4 ,it is thus exceedingly simple in composition1 being not only a pure substance but1 in addition1 an elementary substance4 ,,corundum1 the second species considered1 was a little more complex1 having two elements1 aluminum and oxygen1 in its make-up1 but completely and definitely combined in a new compound that resembles neither aluminum nor oxygen4 ,it is thus a compound substance4 ,no other element than carbon affords any gem-stone when by itself4 ,,oxides ,,of ,,metals4 ,there is1 however1 another oxide1 in addition to aluminum oxide1 that furnishes gem material4 ,it is silicon oxide1 containing the two elements silicon and oxygen4 ,silicon itself is a dark1 gray1 crystalline element that seems half metallic1 half non-metallic in its properties4 ,it is never found by itself in nature but about twenty-eight per cent4 of the crust of the earth is composed of it in compound forms1 and one of the most abundant of these is ,,quartz1 which is a mineral species1 and which contains just silicon and oxygen4 ,that is1 it is oxide of silicon4 ,now quartz is colorless when pure 7rock crystal71 but it is frequently found colored purple 7probably by oxide of manganese7 and it is then called amethyst by the jeweler4 ,at other times its color is yellow 7due to oxide of iron7 and then the jeweler is prone to call it topaz1 although properly speaking that name should1 as we shall soon see1 be reserved for an entirely different mineral species4 ,chalcedony too 7which when banded furnishes us our agates1 and when reddish our carnelian7 is a variety of quartz1 and prase is only quartz colored green by fibers of actinolite within it4 ,the common cat's-eye and the tiger's-eye are varieties of quartz enclosing fibrous minerals or replacing them while still keeping the arrangement that they had4 ,venus hair stone is quartz containing needle-like crystals of rutile1 and iris is quartz that has been crackled within1 so as to produce rainbow colors1 because of the effects of thin layers of material4 ,aventurine quartz 7sometimes called goldstone7 has spangles of mica or of some other mineral enclosed in it4 ,the jaspers are mainly quartz with more of earthy impurity than the preceding stones4 ,thus all this long list of stones of differing names can be classified under the one mineral species1 quartz4 ,together they constitute the quartz gems4 ,in properties they are essentially alike1 having specific gravity #b4ff1 hardness #g1 slight double refraction1 etc41 the slight differences that exist being due only to the presence of varying amounts of foreign matter4 ,,opal4 ,the opal may be considered along with the quartz gems1 because1 like them1 it is composed mainly of oxide of silicon1 but the opal also has water combined with the silicon oxide 7not merely imprisoned in it74 ,thus opal is a hydrous form of silica 7hydrous comes from the ,greek word for water74 ,,spinel4 ,all our other stones are of more complicated chemical composition than the preceding4 ,coming now to mineral species which have three chemical elements in them we may consider first spinel1 which has the two metallic elements aluminum and magnesium and the non-metallic element oxygen in it4 ,it is virtually a compound of the two oxides1 aluminum oxide and magnesium oxide4 ,the variously colored spinels1 like the various corundums1 all have the same properties1 thus they are all of hardness #h or a little higher1 they all have single refraction1 and all have specific gravity #c4fj4 ,,chrysoberyl4 ,another mineral species which1 like spinel1 has just three elements in its composition is chrysoberyl4 ,this mineral contains the metals aluminum and beryllium combined with the non-metal oxygen4 ,thus it is really to be regarded as a compound of the two oxides1 aluminum oxide and beryllium oxide4 ,this species furnishes us ,alexandrite1 chrysoberyl cat's-eye and less valuable chrysoberyls of yellowish-green color4 ,all are of the one species1 the marked color difference being due to the presence of different impurities4 ,the cat's-eye effect in one of the varieties is due to the internal structure rather than to the nature of the material4 ,,the ,,silicates4 ,nearly all of the remaining precious stones belong to a great group of mineral species known as the silicates4 ,these are so called because they consist largely of oxide of silicon 7the material above referred to under quartz gems74 ,this oxide of silicon is not free and separate in the silicates but is combined chemically with other oxides1 chiefly with metallic oxides4 ,thus there are many different silicates because1 in the earth1 many different metallic oxides have combined with silicon oxide4 ,also in many cases two or three or even more metallic oxides have combined with silicon oxide to make single new compounds4 ,,glass1 ,a ,,mixture ,,of ,,silicates4 ,those who are familiar with glass making may receive some help at this point by remembering that the various glasses are silicates1 for they are made by melting sand 7which is nearly pure oxide of silicon7 with various metallic oxides4 ,with lime 7calcium oxide7 and soda 7which yields sodium oxide7 we get soda-lime glass 7common window glass74 ,lead oxide being added to the mixture a dense1 very brilliant1 but soft glass 7flint glass7 results4 ,cut glass dishes and paste gems are made of this flint glass4 ,now the glasses1 although they are silicates1 are not crystalline1 but rather they are amorphous1 that is1 without any definite structure4 ,nature's silicates1 on the other hand1 are usually crystallized or at least crystalline in structure4 7,in a few cases we find true glasses1 volcanic glass1 or obsidian1 for example47 ,having thus introduced the silicates we may now consider which ones among the many mineral silicates furnish us with precious or semi-precious stones4 ,,beryl1 ,,emerald1 ,,and ,,aquamarine4 ,first in value among the silicates is beryl1 which1 when grass green1 we call emerald4 ,the aquamarine and golden beryl too belong to this same species4 ,beryl is a silicate of aluminum and beryllium4 ,that is1 it is a compound in which oxide of silicon is united with the oxides of aluminum and of beryllium4 ,there are thus four chemical elements combined in the one substance and it is hence more complicated in its composition than any of the gems that we have yet considered4 ,it is worthy of note that aluminum occurs in the majority of precious stones1 the only species so far considered that lack it being diamond1 and the quartz gems4 ,perhaps the silicates that are next in importance to the jeweler1 after beryl1 are those which form the garnets of various types4 ,there are four principal varieties of garnet 7although specimens of garnet frequently show a crossing or blending of the types74 ,,garnets4 ,the types are 7#a7 ,almandite garnet2 7#b7 ,pyrope garnet2 7#c7 ,hessonite garnet2 and 7#d7 ,andradite garnet4 ,these are all silicates1 the almandite garnets being silicates of iron and aluminum2 the pyrope garnets are silicates of magnesium and aluminum2 the hessonite garnets1 silicates of calcium and aluminum1 and the andradite garnets1 silicates of calcium and iron4 ,the so-called almandine garnets of the jeweler are frequently of the almandite class and tend to purplish red4 ,the pyrope garnets are1 as the name literally implies1 of fire red color1 as a rule1 but they also may be purplish in color4 ,the hessonite garnets are frequently brownish red and are sometimes called cinnamon stones4 ,the andradite garnets furnish the brilliant1 nearly emerald green demantoids 7so often called olivine by the trade74 ,thus all the garnets are silicates and yet we have these four principal mineral species1 which1 however1 are more closely related to each other in crystal form1 in character of composition and in general properties1 than is usual among the other silicates4 ,specimens which have any one of the four types of composition unblended with any of the other types would be found to be exactly alike in properties4 ,as was suggested above1 however1 there is a great tendency to blend and this is well illustrated by the magnificent rhodolite garnets1 of rhododendron hue which were found in ,macon ,county1 ,north ,carolina4 ,these had a composition between almandite and pyrope1 that is1 they had both magnesium and iron with aluminum and silica4 ,the true ,,topaz next calls for consideration as it too is a silicate4 ,the metallic part consists of aluminum1 and there are present also the non-metals fluorine and hydrogen4 ,here we have five elements in the one substance4 ,various specimens of this species may be wine yellow1 light blue1 or bluish green1 pink or colorless1 yet they all have essentially the same properties4 ,,tourmaline is about as complicated a mineral as we have4 ,it is a very complex silicate1 containing aluminum1 magnesium1 sodium 7or other alkali metal1 as1 for example1 lithium71 iron1 boron1 and hydrogen4 ,as ,ruskin says of it in his ,the ,ethics of the ,dust1 when ,mary asks and what is it made of8 ,a little of everything2 there's always flint 7silica7 and clay 7alumina7 and magnesia in it and the black is iron1 according to its fancy2 and there's boracic acid1 if you know what that is3 and if you don't1 ,i cannot tell you to-day and it doesn't signify2 and there's potash and soda2 and on the whole1 the chemistry of it is more like a medival doctor's prescription1 than the making of a respectable mineral4 ,the various tourmalines very closely resemble each other in their properties1 the slight differences corresponding to differences in composition do not alter the general nature of the material4 ,,moonstone belongs to a species of mineral known as feldspar4 ,the particular feldspar that furnishes most of the moonstone is orthoclase1 a silicate of potassium and aluminum4 ,another feldspar sometimes seen as a semi-precious stone is ,labradorite4 ,amazonite1 also1 is a feldspar4 ,sunstone is a feldspar which includes tiny flakes or spangles of some other mineral4 ,the mineral species olivine gives us peridot4 ,it is a silicate of magnesium4 ,,zircon is itself a species of mineral and is a silicate of zirconium4 ,the names hyacinth1 jacinth1 and jargoon are applied to red1 yellow1 and colorless zircon in the order as given4 ,,jade may be of any of several different species of minerals1 all of which are very tough4 ,the principal jades belong1 however1 to one or the other of two species1 jadeite and nephrite4 ,jadeite is a sodium aluminum silicate and nephrite1 a calcium magnesium silicate4 ,leaving the silicates we find very few gem minerals remaining4 ,the phosphates furnish us turquoise1 a hydrous aluminum phosphate1 with copper and iron4 ,variscite is also a phosphate 7a hydrated aluminum phosphate74 ,the carbonates give us malachite and azurite1 both carbonates of copper with combined water1 the malachite having more water4 ,,lesson ,,xix ,,the ,,naming ,,of ,,precious ,,stones ,owing to the confusion which may result from a lack of uniformity in the naming of precious stones1 it is very desirable that jewelers and stone merchants inform themselves in regard to the correct use of the names of the gems1 and that they use care in speaking and in writing such names4 ,as nearly all precious and semi-precious stones are derived from a relatively small number of mineral species1 as we saw in ,lesson ,,xviii41 and as the science of mineralogy has a very orderly and systematic method of naming the minerals1 the best results are had in the naming of gems when we use1 as far as is possible1 the language of mineralogy4 ,,ancient ,,usage4 ,long established custom and usage1 however1 must be observed1 for any system of naming must be generally understood in order to be useful4 ,thus the proper name for blood red1 crystallized oxide of aluminum1 of gem quality1 according to the mineralogical system of naming1 would be red corundum1 but that same material is referred to in the ,old ,testament thus 7in speaking of wisdom71 ,she is more precious than rubies4 ,it is obviously necessary to keep and to use all such terms as have been for years established in usage1 even though they do not agree with the scientific method of naming the particular mineral4 ,it is1 however1 necessary that any name1 thus retained1 should be correctly used1 and that it should not be applied to more than one material4 ,thus the term ruby should be reserved exclusively for red corundum1 and not applied to other red minerals such as garnet1 spinel1 etc41 as is too often done4 ,it will be the purpose of this lesson to attempt to set forth as clearly and as briefly as possible what constitutes good usage in the naming of the principal stones1 and also to point out what incorrect usage is most in need of being avoided4 ,to cover the subject systematically we will adopt the order of hardness that we did in discussing mineral species in ,lesson ,,xviii4 ,,fancy ,,diamonds4 ,beginning with the hardest of all gems1 the diamond1 we have no difficulty as regards naming1 as all specimens of this mineral1 regardless of color1 are called diamonds4 ,when it is necessary to designate particular colors or tints1 or differences in tint1 additional names are used--for example1 all diamonds of pronounced and pleasing color are called fancy diamonds in the trade4 ,certain of these fancy diamonds are still further defined by using a name specifying the color1 as1 for example1 canary diamonds 7when of a fine bright yellow71 or golden fancies1 when of a fine golden brown1 or orange1 or pink1 or absinthe green1 or violet1 as the case may be4 ,,names ,,of ,,various ,,grades ,,of ,,white ,,diamonds4 ,the great majority of the diamonds which come on the market as cut stones belong1 however1 to the group which would be spoken of as white diamonds1 but many qualifying names are needed to express the degree of approach to pure white possessed by different grades of these diamonds4 ,thus the terms3 #a1 ,jgers2 #b1 ,rivers2 #c1 ,blue ,wesseltons2 #d1 ,wesseltons2 #e1 ,top ,crystals2 #f1 ,crystals2 #g1 very light brown2 #h1 ,top ,silver ,capes2 #i1 ,silver ,capes2 #aj1 ,capes2 #aa1 ,yellows1 and #ab1 ,browns1 describe increasing depth of color1 and hence decreasing value in diamonds4 ,,popular ,,names4 ,certain more popular names for diamonds of differing degrees of whiteness may next be set forth4 ,the term blue white 7a much abused expression1 by the way7 should be applied only to diamonds of such a close approach to pure whiteness of body substance1 as seen on edge in the paper that1 when faced up and undimmed1 they give such a strong play of prismatic blue that any slight trace of yellow in their substance is completely disguised1 and the effect upon the eye is notably blue4 ,this would be the case with stones of the grades from #a through #d in the list above4 ,grades #e and #f might properly be called fine white1 and grades #g1 #h1 and #i simply white4 ,grade #aj is frequently spoken of as commercial white1 and grade #aa sometimes as off color4 ,grade #ab includes all degrees of brownness except the very light shades and the deep1 pretty shades of the fancy browns4 ,,rubies4 ,leaving the naming of the different colors of diamonds we come to the gems furnished us by the mineral known as corundum4 ,as we have previously seen1 this mineral occurs in many different colors and with wide differences of tint and shade in each of the principal colors4 ,the best practice with regard to naming the corundum gems is to call the red material1 when of a good1 full red of pleasing shade1 ruby4 ,the finest shades of blood red are usually called ,burmah rubies because more rubies of this quality are found in ,burmah than anywhere else4 ,any ruby of the required shade would1 however1 be called a ,burmah ruby in the trade regardless of its geographical origin4 ,the most desirable tint among ,burmah rubies is that which is known as pigeon blood in color4 ,this color is perhaps more accurately defined as like the color in the center of the red of the solar spectrum4 ,certain slightly deeper red rubies are said to be of beef blood color4 ,the ,english are said to prefer these4 ,those of slightly lighter tint than pigeon blood are sometimes referred to as of ,french color1 from the fact that they are preferred by ,french connoisseurs4 ,rubies of dark1 garnet-like shade are known as ,siam rubies1 many such being found in that country4 ,light pinkish rubies are called ,ceylon rubies4 ,it should be clearly kept in mind that all these rubies are of red corundum1 and that in all their distinctive properties except color they are essentially similar4 ,,sapphires4 ,corundum of fine blue color is known as sapphire4 ,the cornflower blue seems to be most in favor at present4 ,such sapphires are sometimes called ,kashmir sapphires because many fine ones come from that ,state4 ,ceylon sapphires are usually paler than the cornflower blue4 ,montana sapphires are usually of greenish blue or pale electric blue4 ,such fine blue stones as are mined in ,montana would be sold under another name according to the quality of their color1 and not as ,montana sapphires4 ,australian sapphires are of a very deep1 inky blue1 and do not command a high price4 ,here again1 as with rubies1 the classification depends upon the color rather than upon the origin1 although the geographical names that are used1 correctly state the usual source of stones of the particular color4 ,all corundums other than ruby and blue sapphire are usually called by the term sapphire1 with a qualifying adjective designating the color2 thus we may have pink sapphire1 golden sapphire1 green sapphire1 etc4 ,when of very fine yellow color the yellow sapphire is sometimes called ,oriental topaz by jewelers1 the term ,oriental as thus used indicating that the material is corundum4 ,we also have ,oriental amethyst and ,oriental emerald for the purple1 and the fine green1 and ,oriental aquamarine for the light blue-green corundum4 ,the yellow corundum is also sometimes called ,king topaz1 especially in ,ceylon4 ,inferior sapphires of almost every conceivable color are frequently assorted in lots and sold as fancy sapphires4 ,such lots1 however1 almost always need reclassification as they often contain as many as a dozen mineral species besides corundum4 ,sapphires and rubies of minute tubular internal structure frequently display a beautiful six-pointed star when cut to a round-topped cabochon shape and exposed to direct sunlight or to light from any other single source4 ,such stones are named star sapphire and star ruby4 ,the artificial rubies and sapphires should all be called scientific ruby or sapphire1 and not reconstructed or synthetic as none are made to-day from small1 real rubies1 and as the process is in no sense a chemical synthesis4 ,,chrysoberyl4 ,leaving the corundum gems we come next to chrysoberyl4 ,when the gems furnished by this mineral are of a fine green by daylight1 and of a raspberry red by artificial light1 as is sometimes the case1 they should be called ,alexandrites 7after the ,czar ,alexander ,,ii41 in whose dominions1 and on whose birthday1 the first specimens are said to have been discovered74 ,when chrysoberyl is of fibrous or tubular internal structure it affords cat's-eyes 7when cabochon cut71 and these should be specifically named as chrysoberyl cat's-eye to distinguish them from the less beautiful and less valuable quartz cat's-eyes4 ,other varieties of chrysoberyl 7most of those marketed are of a greenish-yellow color7 are correctly named simply chrysoberyls4 ,such stones are1 however1 sometimes incorrectly called chrysolite by the trade1 and this practice should be corrected1 as the term chrysolite applies correctly only to the mineral olivine which gives us the peridot4 ,,spinel4 ,next in the order that we have chosen comes spinel4 ,the more valuable spinels are of a red color that somewhat closely approaches the red of some rubies4 ,such red spinels should be called ,ruby spinel 7and not spinel ruby74 ,the stones themselves sometimes get mixed with corundum rubies 7they are frequently found in the same gem gravels71 and this makes it all the more necessary that both stones and names should be clearly distinguished4 ,some dealers call reddish spinels ,balas ruby 7rose red71 and orange red ones rubicelle4 ,violet red spinel is sometimes called almandine spinel4 ,it is very desirable that the name of the mineral species1 spinel1 should be used1 together with a qualifying color adjective1 in naming gems of this species1 rather than such terms as rubicelle1 balas ruby1 spinel ruby1 etc4 ,,topaz4 ,we come now to topaz4 ,true1 or precious topaz1 as it is usually called1 to distinguish it from the softer and less valuable yellow quartz1 is seldom seen in the trade to-day4 ,jewelers almost always mean yellow quartz when they speak of topaz4 ,this is an unfortunate confusion of terms1 and one which will be hard to eradicate4 ,there is seldom any injustice done through this misnaming1 as the price charged is usually a fair one for the material offered4 ,considerably higher prices would be necessary if true topaz was in question4 ,an instance from the writer's experience will serve to illustrate the confusion that exists in the trade as to what should be called topaz4 ,a jeweler of more than ordinary acquaintance with gems exhibited some fine brooch stones as specimens of topaz4 ,on remarking that they were of course citrine quartz rather than true topaz1 the author was met with the statement that the brooch stones were real topaz4 ,in order to make clear to the dealer the difference between the two species1 the author asked him if he hadn't some smaller topazes in stock that had cost him considerably more than the brooch stones4 ,the dealer replied that he had some small wine yellow topazes for which he had paid more1 and he produced them4 ,the latter stones were true ,brazilian topazes4 ,most of them had tiny1 crackly flaws in them1 as is frequently the case1 and1 as the writer pointed out to the dealer1 they had been bought by the carat1 whereas the large brooch stones had been bought at a certain price per pennyweight4 ,in fact the little stones had cost more per carat than the larger ones had per pennyweight4 ,the dealer was then asked if there must not be some difference in the real nature of the two lots to justify paying more per carat for small1 imperfect stones than per pennyweight for large perfect ones4 ,he of course acknowledged that it would appear reasonable that such was the case4 ,he was next shown that his small true topazes scratched his large stones easily1 but the large ones could get no hold upon the surfaces of the small ones4 7,it will be remembered that topaz has a hardness of #h1 while quartz has a hardness of #g47 ,the explanation then followed that the two lots were from two entirely distinct minerals1 topaz and quartz1 and that the former was harder1 took a somewhat better polish1 and was more rare 7in fine colors7 than quartz4 ,of course the yellow quartz should be sold under the proper name1 citrine quartz4 7,from the same root that we have in citrus as applied to fruits4 ,for example the ,california ,citrus ,fruit ,growers' ,association1 which sells oranges1 lemons1 grape fruit1 etc4 ,the color implication is obvious47 ,if the jeweler still wishes to use the term topaz because of the familiarity of the public with that name1 then he should at least qualify it in some way4 ,one name that is current for that purpose is ,spanish topaz1 another is ,quartz-topaz4 ,perhaps the latter is the least objectionable of the names that include the word topaz4 ,some of the wine yellow true topazes lose the yellow1 but retain the pink component1 on being gently heated4 ,the resulting pink stone is rather pretty and usually commands a higher price than the yellow topazes4 ,such artificially altered topazes should be sold only for what they are1 and probably the name pinked topaz1 implying1 as it does1 that something has been done to the stone1 is as good a name as any4 ,there is1 however1 little chance of fraud in this connection1 as natural pink topazes are not seen in the trade1 being very rare4 ,some bluish-green topaz is said to be sold as aquamarine1 and this confusion of species and of names should1 of course1 be stopped by an actual determination of the material as to its properties4 ,lacking a refractometer1 the widely differing specific gravities of the two minerals would easily serve to distinguish them4 ,,lesson ,,xx ,,the ,,naming ,,of ,,precious ,,stones 7,concluded7 ,,beryl1 ,,emerald1 ,,aquamarine4 ,coming now to beryl we have first emerald1 then aquamarine1 then beryls of other colors to consider4 ,there is too often a tendency among dealers to confuse various green stones1 and even doublets1 under the name emerald4 ,while the price charged usually bears a fair relation to the value of the material furnished1 it would be better to offer tourmaline1 or peridot 7the mineral name of which is olivine71 or demantoid garnet 7sometimes wrongly called ,olivine71 or emerald doublets1 or emerald or imitation emerald1 as the case might be1 under their own names4 ,there are no true synthetic or scientific or reconstructed emeralds1 and none of these terms should be used by the trade4 ,there has been an effort made in some cases to do business upon the good reputation of the scientific rubies and sapphires1 but the products offered1 when not out and out glass imitations1 have usually been doublets or triplets1 consisting partly of some pale1 inexpensive1 natural mineral1 such as quartz or beryl1 and a layer of deep green glass to give the whole a proper color4 ,all attempts to melt real emerald or beryl have yielded only a beryl glass1 softer and lighter than true emerald1 and not crystalline1 but rather glassy in structure4 ,hence the names reconstructed1 synthetic and scientific should never be applied to emerald4 ,the light green and blue green beryls are correctly called aquamarines1 the pale sky-blue beryls should be named simply blue beryl4 ,yellow beryl may be called golden beryl1 or it may be called heliodor1 a name that was devised for the fine yellow beryl of ,madagascar4 ,beautiful pink beryl from ,madagascar has been called morganite1 a name that deserves to live in order to commemorate the great interest taken by ,j4 ,pierpont ,morgan in collecting and conserving for future generations many of the gems in the ,american ,museum of ,natural ,history in ,new ,york4 ,,zircon4 ,we now come to a number of minerals slightly less hard than beryl1 but harder than quartz1 and zircon is perhaps as hard as any of these1 so it will be considered next4 ,red zircon1 which is rare1 is properly called hyacinth4 ,many ,hessonite garnets 7cinnamon stones7 are incorrectly called hyacinths1 however4 ,the true hyacinth has more snap and fire owing to its adamantine surface luster and high dispersive power1 as well as to its high refractive index4 ,a true hyacinth is a beautiful stone4 ,golden yellow zircons are correctly called jacinths4 ,artificially whitened zircons 7the color of which has been removed by heating7 are known as jargoons or sometimes as ,matura diamonds4 ,all other colors in zircon should be named simply zircon1 with a color adjective to indicate the particular color as1 brown zircon1 etc4 ,,tourmaline4 ,tourmaline furnishes gems of many different colors4 ,these are all usually called simply tourmaline1 with a color adjective to specify the particular color1 as1 for example1 the pink tourmaline of ,california4 ,red tourmaline is1 however1 sometimes called rubellite1 and white tourmaline has been called achroite4 ,the latter material is seldom cut1 and hence the name is seldom seen or used4 ,,garnet4 ,we may next consider the garnets1 as most of them are somewhat harder than quartz4 ,as was said in ,lesson ,,xviii4 in our study of mineral species1 there are several types of garnets1 characterized by similarity of chemical composition1 or at least by analogy of composition1 but1 having specific differences of property4 ,the names used by jewelers for the several types of garnets ought to be a fairly true indication as to the type in hand in a particular case4 ,at present there is considerable confusion in the naming of garnets4 ,the most common practice is to call all garnets of a purplish-red color almandines4 ,as many such garnets belong to the mineral species almandite garnet1 there is little objection to the continuance of this practice4 ,the somewhat less dense1 and less hard blood red garnets are properly called pyrope garnets 7literally fire garnets74 ,many of the ,arizona garnets belong in this division4 ,the term ,arizona rubies should not be used4 ,as was said under ruby1 nothing but red corundum should receive that title4 ,similarly the pyrope garnet of the diamond mines of ,south ,africa is incorrectly called ,cape ruby4 ,pyrope and almandite garnet tend to merge in composition and in properties1 and the beautiful ,rhodolite garnets of ,macon ,county1 ,north ,carolina1 are between the two varieties in composition1 in color1 and in other properties4 ,hessonite garnet furnishes yellowish-red and brownish-red stones1 which are sometimes also called cinnamon stones4 ,they are also frequently and incorrectly called jacinth or hyacinth1 terms which1 as we have seen1 should be reserved for yellow and red zircon1 respectively4 ,andradite garnet furnishes brilliant green stones1 which have been incorrectly named ,olivines by the trade4 ,the name is unfortunate as it is identical with the true name of the mineral which gives us peridot4 ,the name does not even suggest the color of these garnets correctly1 as they are seldom olive green in shade4 ,as the scarcity of fine specimens and their great beauty make a fairly high price necessary1 the public would hardly pay it for anything that was called garnet1 as garnets are regarded as common and cheap4 ,perhaps the adoption of the name ,demantoid might relieve the situation4 ,the stones are frequently referred to as demantoid garnets on account of their diamond-like luster and dispersion4 ,the use of demantoid alone1 if a noun may be made from the adjective1 would avoid both the confusion with the mineral olivine1 and the cheapening effect of the word garnet1 and would at the same time suggest some of the most striking properties of the material4 ,spodumene furnishes pink to lilac ,kunzite1 named after ,dr4 ,george ,f4 ,kunz1 the gem expert1 and for a time an emerald green variety was had from ,north ,carolina which became known as ,hiddenite1 after its discoverer1 ,w4 ,e4 ,hidden4 ,no confusion of naming seems to have arisen in regard to this mineral4 ,the next mineral in the scale of hardness is quartz4 7,hardness #g47 ,when pure and colorless it should be called rock crystal4 ,purple quartz is of course amethyst4 ,some dealers have adopted a bad practice of calling the fine deep purple amethyst ,oriental amethyst1 which should not be done1 as the term ,oriental has for a long time signified a corundum gem4 ,as ,siberia has produced some very fine amethysts1 the term ,siberian amethyst would be a good one to designate any especially fine gem4 ,,quartz ,,gems4 ,we have already considered the naming of yellow quartz in connection with topaz4 ,citrine quartz is probably the best name for this material4 ,if it is felt that the name topaz must be used1 the prefix quartz should be used1 or perhaps ,spanish topaz will do1 but some effort should be made to distinguish it from the true precious topaz4 ,in addition to amethyst and citrine quartz we have the pinkish1 milky quartz known as rose quartz4 ,this is usually correctly named4 ,cat's-eye is a term that should be reserved for the ,chrysoberyl variety1 and the quartz variety should always be called quartz cat's-eye4 ,tiger's-eye is a mineral in which a soft fibrous material has been dissolved away1 and quartz has been deposited in its place4 ,aventurine quartz is the correct name for quartz containing spangles of mica4 ,clear1 colorless pebbles of quartz are sometimes cut for tourists4 ,such pebbles are frequently misnamed diamonds with some prefix1 as for example ,lake ,george diamonds1 etc4 ,among the minutely crystalline varieties of quartz we have the clear red1 which should be called carnelian1 the brownish-red sard1 the green chrysoprase1 the leek green prase1 and the brighter green plasma4 ,the last three are not so commonly seen as the first two1 and frequently the best-colored specimens are artificially dyed4 ,jasper1 a material more highly regarded by the ancients than at present1 is mainly quartz1 but contains enough earthy material to make it opaque4 ,bloodstone is a greenish chalcedony with spots of red jasper4 ,agates are banded chalcedonies1 the variety called onyx having very regular bands1 and the sardonyx being an onyx agate in which some of the bands are of reddish sard4 ,just as we considered opal with quartz 7because of its chemical similarity7 when discussing mineral species1 so we may now consider the proper naming of opals here4 ,precious opal is distinguished from common opal by the beauty of its display rather than by any difference in composition4 ,the effect is of course due to the existence of thin films 7probably of material of slightly different density71 filling what once were cracks in the mass4 ,the rainbow colors are the result of interference of light 7see a college text on physics for an explanation of interference74 ,the varying thickness of these films gives varying colors1 so different specimens of opal show very different effects4 ,the differences of distribution of the films within the material also cause variations in the effects4 ,hence we have hardly any two specimens of opal that are alike4 ,there are1 however1 certain fairly definite types of opal and jewelers should learn to apply correct names to these types4 ,most prominent among the opals of to-day are the so-called ,black opals from ,new ,south ,wales4 ,these give vivid flashes of color out of seeming darkness4 ,in some positions the stones1 as the name implies1 appear blue-black or blackish gray4 ,by transmitted light1 however1 the bluish stones appear yellow4 ,owing to the sharp contrast between the dark background and the flashing spectrum colors1 black opals are most attractive stones and fine specimens command high prices4 ,one fine piece1 which was on exhibition at the ,panama-,pacific ,exposition was in the shape of an elongated shield1 about #a-c_/d inches by #a-a_/h inches in size and rather flat and thin for its spread4 ,it gave in one position a solid surface of almost pure ruby red which changed to green on tipping the stone to the opposite direction2 #b1jjj was asked for the piece4 ,white opal is the name applied to the lighter shades of opal which do not show the bluish-black effect in any position4 ,harlequin opal has rather large areas of definite colors giving somewhat the effect of a map of the ,united ,states in which the different ,states are in different colors4 ,fire opal is an orange-red variety4 ,it has some play of colors in addition to its orange-red body color4 ,opal ,matrix has tiny specks and films of precious opal distributed through a dark volcanic rock and the mass is shaped and polished as a whole4 ,,jade4 ,jade should next receive attention4 ,it is a much abused term4 ,under it one may purchase jadeite1 nephrite1 bowenite1 amazonite1 or frequently simply green glass4 ,the use of the word ought to be confined to the first two minerals mentioned1 namely1 jadeite and nephrite1 for they only possess the extreme toughness together with considerable hardness that we expect of jade4 ,bowenite1 while tough1 is relatively soft and amazonite is brittle and also easily cleavable1 while glass is both soft and brittle4 ,,peridot ,,and ,,olivine4 ,the mineral olivine gives us the peridot 7this name should be kept for the deeper bottle green stones71 and the olive green gems of this same mineral may correctly be called olivine or chrysolite4 ,as was explained under garnet1 jewelers frequently use the term olivine to designate demantoid garnet4 ,the term chrysolite is also sometimes incorrectly used for the greenish-yellow chrysoberyl4 ,,feldspar ,,gems4 ,among the minerals softer than quartz1 which are used as gems1 we have also feldspar1 which gives us moonstone1 ,labradorite1 and ,amazonite4 ,an opalescent form of chalcedony is frequently gathered on ,california beaches and polished for tourists under the name of ,california ,moonstone4 ,this name is unfortunately chosen as the material is not the same as that of true moonstone and the effect is not so pronounced or so beautiful4 ,the polished stones show merely a milky cloudiness without any of that beautiful sheen of the true moonstone4 ,labradorite is usually correctly named4 ,amazonite was originally misnamed1 as none is found along the river of that name4 ,the term has come into such general use1 however1 that we shall probably have to continue to use it1 especially as no other name has come into use for this bluish-green feldspar4 ,as has already been said1 amazonite is sometimes sold as jade1 which is incorrect4 ,,malachite1 ,,azurite1 ,,and ,,lapis ,,lazuli4 ,malachite and azurite are usually correctly named1 but lapis lazuli is a name that is frequently misused1 being applied to crackled quartz that has been stained with ,prussian blue1 or some other dye1 to an unconvincing resemblance to true lapis4 ,such artificially produced stones are sometimes sold as ,swiss lapis4 ,they are harder than true lapis and probably wear much better in exposed ornaments1 but they are not lapis and are never of equal color1 and names should not be misused1 and especially is this true in a trade where the public has had to rely so completely upon the knowledge and the integrity of the dealer4 ,with the increase of knowledge about precious stones that is slowly but steadily growing among the public1 it becomes more than ever necessary for the jeweler and gem dealer to know and to use the correct names for all precious stones4 ,the student who wishes to learn more about the matter will have to cull his information from many different works on gems4 ,g4 ,f4 ,herbert-,smith1 in his ,gem-,stones1 gives a three and one half page chapter on ,nomenclature of ,precious ,stones 7,chap4 ,,xiii41 pp4 #aji-aab74 ,the present lesson has attempted to bring together in one place material from many sources1 together with some suggestions from the author4 ,,lesson ,,xxi ,,where ,,precious ,,stones ,,are ,,found ,,occurrence ,,of ,,diamond4 ,every dealer in precious stones should know something of the sources of the gems that he sells4 ,the manner of the occurrence of the rough material is also a matter of interest4 ,it will therefore be the purpose of this lesson to give a brief account of the geographical sources of the principal gems and of their mode of occurrence in the earth4 ,for the sake of uniformity of treatment we will once more follow the descending order of hardness among the gems and we thus begin by describing the occurrence of diamond4 ,it will be of interest to note first that the earliest source of the diamond was ,india1 and that for many years ,india was almost the sole source4 ,tavernier tells us that the diamond mining industry was in a thriving state during the years from #afdj to #afhj1 during which time he made six journeys to ,india to purchase gems4 ,he speaks of ,borneo as another source of diamonds1 but most of the diamonds of that time were furnished by ,india4 ,,golcondas4 ,indian diamonds were noteworthy for their magnificent steely blue-white quality and their great hardness1 and occasionally one comes on the market to-day with an authentic pedigree1 tracing its origin back to the old ,indian mines1 and such stones usually command very high prices4 ,one of a little over seven and one half carats in weight1 in the form of a perfect drop brilliant1 has lately been offered for sale at a price not far from #a1jjj per carat4 ,such diamonds are sometimes called ,golcondas because one of the mining districts from which the fine large ,indian stones came was near the place of that name4 ,some of the stones from the ,jgersfontein mine in ,south ,africa resemble the ,golcondas in quality4 ,many of the large historical crown diamonds of ,europe came from the ,indian mines4 ,the stones were found in a sedimentary material1 a sort of conglomerate1 in which they1 together with many other crystalline materials1 had become imprisoned4 ,their original source has never been determined4 ,they are therefore of the so-called ,river type of stone1 having probably been transported from their original matrix1 after the disintegration of the latter1 to new places of deposit1 by the carrying power of river waters4 ,the ,indian mines now yield very few stones4 ,the ,united ,states ,consular reports occasionally mention the finding of a few scattered crystals but the rich deposits were apparently worked out during the seventeenth century and the early part of the eighteenth century4 ,in #agbe and in the few following years the ,brazilian diamond fields began to supersede those of ,india4 ,like the latter1 the ,brazilian fields were alluvial1 that is1 the materials were deposited by river action after having been carried to some distance from their original sources4 ,,brazilian ,,diamonds4 ,the diamonds of ,brazil also resembled those of ,india in quality1 being on the average better than those of the present ,south ,african mines4 ,it may be added that even the ,african diamonds that are found in river diggings average better in quality than those of the volcanic pipes which form the principal source of the world's supply to-day4 ,there seems to be a superabundance of iron oxide in the rocks of the ,african mines and in the diamonds themselves1 imparting yellow or brownish tints to the material4 ,the ,river stones seem to have lost this color to a considerable extent1 if they ever had it4 ,possibly long extraction with water has removed the very slightly soluble coloring material4 ,whatever the cause of their superiority ,river stones have always been more highly regarded than stones from the volcanic pipes4 ,brazil furnished the world's principal supply of diamonds until the discovery of the ,african stones in #ahfg4 ,at present relatively small numbers of ,brazilian stones reach the world's markets4 ,most of these come from the great ,bahia district 7discovered in #ahdd7 rather than from the older mines of ,brazil4 ,the present ,brazilian stones average of small size4 ,they are1 however1 of very good quality as a rule4 ,a few green stones are found in ,brazil and these may be of an absinthe-green or of a pistachio-green tint4 ,,australian ,,and ,,american ,,sources4 ,while a few diamonds now come on the market from ,new ,south ,wales1 and while an occasional stone is found in the ,united ,states 7usually in glacial drift in the north central ,states1 or in volcanic material somewhat resembling that of ,south ,africa in ,arkansas7 yet the world's output now comes almost entirely from ,south ,africa and mainly from the enormous volcanic pipes of the ,kimberly district and those of the ,premier ,co4 in the ,transvaal4 ,,south ,,african ,,diamonds4 ,the nature of the occurrence of diamond in the pipes of ,south ,africa is so well known to all who deal in diamonds to-day that but little space need be devoted to it4 ,the blue ground1 as the rock in which the diamonds are found is called1 seems to have been forced up from below1 perhaps as the material of a mud volcano1 bringing with it the diamonds1 garnets1 zircons1 and the fifty or more other minerals that have been found in the blue ground4 ,the fragmentary character of some of these minerals would indicate that the blue ground was not their original matrix4 ,how the diamonds originally crystallized and where1 is still probably a matter for further speculation4 ,while at first the mines were worked1 like quarries1 from the surface1 and while the great ,premier mine is still so worked1 most of the present mines are worked by sinking shafts in the native rock outside of the blue ground and then tunneling into the diamond-bearing rock laterally1 removing it to the surface1 allowing it to weather on the floors until it crumbles1 then crushing and washing it and concentrating the heavy minerals by gravity methods4 ,large diamonds are then picked out of the concentrates by hand and small ones and fragments are removed by the greasers1 which are shaking tables heavily smeared with grease over which the concentrates are washed and to which diamond alone1 of all the minerals in the concentrate1 sticks4 ,the grease is periodically removed and melted1 and the diamonds secured4 ,the grease can then be used again4 ,german ,south ,west ,africa furnishes a considerable output of very small diamonds1 which are found in dry sand far from any present rivers4 ,these diamonds cut to splendid white melee and the output is large enough to make some difference in the relative price of small stones as compared to large ones4 ,the ,south ,west ,african field seldom yields a stone that will afford a finished quarter-carat diamond4 ,,rubies4 ,passing on to the occurrence of the corundum gems we will consider first the ruby4 ,most fine rubies come from ,burmah4 ,the district in which they are found is near ,mogok4 ,practically all the fine pigeon-blood rubies come from this district4 ,the fashion for red stones being for the time little in evidence rubies are not now in great demand4 ,this cessation of demand can hardly be laid to the competition of the scientific ruby1 for the sapphire is now very much in vogue1 yet scientific sapphires resemble the natural ones even more closely than do the rubies4 ,siam furnishes a considerable number of dark garnet-like rubies4 ,these do not command high prices4 ,they are1 however1 sometimes very beautiful1 especially when well cut for brilliancy1 and when in a strong light4 ,ceylon furnishes a few rubies and a few red corundums have been found in ,north ,carolina4 ,the ,burmese rubies appear to have been formed in a limestone matrix1 but most of those obtained are gotten from the stream beds1 where they have been carried by water after weathering out from the mother rock4 ,the rubies of ,ceylon1 too1 probably originated in a limestone matrix1 but are sought in stream gravels4 ,,sapphires4 ,fine blue sapphires originate in ,siam in larger numbers than in any other locality4 ,kashmir1 in ,india1 also supplies splendid specimens of large size4 ,ceylon1 too1 furnishes a good deal of sapphire1 but mostly of a lighter color than the ,kashmir sapphire4 ,the ,ceylon sapphires are found in the streams1 but originate in rock of igneous origin4 ,montana furnishes considerable quantities of sapphire1 some of which is of very good color4 ,it is1 of course1 as good as the ,oriental if of equal color1 being of the same material4 ,the better colored sapphire from ,montana is mined from the rock4 ,most of the sapphires found in the river gravels near ,helena1 ,mont41 are greenish blue or of other colors1 and not of fine blue4 ,queensland and ,victoria in ,australia supply considerable quantities of sapphire4 ,when blue the ,australian sapphire is usually too dark to be very valuable4 ,the golden and other fancy sapphires of the trade come largely from the ,ceylon gravels4 ,siam yields silky brown stones and some fine green ones4 ,some of the ,australian sapphires when cut in certain directions yield green stones4 ,,chrysoberyl4 ,chrysoberyl of the variety ,alexandrite now comes mainly from ,ceylon1 although formerly from the ,ural ,mountains4 ,the cat's-eyes also come chiefly from ,ceylon4 ,the yellowish-green chrysoberyls 7which jewelers sometimes call chrysolite7 come both from ,ceylon and from ,brazil4 ,they are frequently found in papers of fancy sapphires or fancy color stones1 so called4 ,,spinel4 ,spinels are found along with ruby in ,burmah and in ,siam and they also occur in the gem gravels of ,ceylon4 ,limestone is the usual matrix of spinel1 although it is more often mined in gravels resulting from the weathering of the matrix4 ,,topaz4 ,true topaz1 of wine-yellow color1 comes mostly from ,brazil4 ,ceylon also furnishes yellow topaz4 ,asiatic ,russia furnishes fine large blue or blue-green crystals resembling aquamarine in appearance4 ,most of the topaz found in other localities is pale or colorless4 ,several of our western ,states1 notably ,utah1 ,colorado1 and ,california1 furnish colorless topaz4 ,mexico and ,japan also produce it4 ,it is seldom cut1 for1 while producing a rather brilliant stone1 it has little fire and is therefore not very attractive4 ,,emerald ,,and ,,aquamarine4 ,beryl of the emerald variety is exceedingly scarce in the earth4 ,most of the best emerald comes from ,colombia1 ,south ,america4 ,large crystals of paler color come from the ,urals4 ,like ruby and spinel1 emerald usually originates in limestone4 ,one is tempted to suspect that these stones are of aqueous origin and that sapphires1 and beryl1 other than emerald1 are more likely of igneous origin4 ,beryls of the aquamarine type occur in many places1 but usually of too pale a tint1 or too imperfect1 to be worthy of cutting4 ,fine gem beryl of blue and blue-green tints comes from ,siberia and from several places in the ,ural ,mountains on their ,asiatic slopes4 ,the ,minas ,geraes district of ,brazil1 famous for all kinds of gem stones1 furnishes most of the aquamarine of commerce4 ,the pegmatite dikes of ,haddam ,neck1 ,conn41 of ,stoneham1 ,me41 and of ,san ,diego ,county1 ,cal41 have furnished splendid aquamarine and other beryl4 ,these dikes1 according to the geological evidence1 are the result of the combined action of heat and water4 ,thus both melting and dissolving went on together and as a result many fine gem minerals of magnificent crystallization were formed during the subsequent cooling4 ,the longer the cooling lasted and the more free space for growth the crystals had1 the larger and more perfect they got4 ,the author has himself obtained finely crystallized aquamarine and tourmaline from the ,haddam1 ,conn41 locality and the best specimens there occur in pockets or cavities in the coarse granite4 ,within1 these pockets are lined with crystals of smoky quartz1 tourmaline1 beryl1 and other minerals4 ,sometimes crystals occur in mud or clay masses inside the cavities and such crystals1 having been free to grow uninterruptedly in every direction1 were perfect in form1 being doubly terminated1 and not attached anywhere to the rock4 ,madagascar has in recent years furnished the finest pink beryl1 which has been named ,morganite4 ,yellow beryl 7,heliodor7 and aquamarine also occur in ,madagascar4 ,,zircon4 ,zircon comes on the market mainly from ,ceylon4 ,it deserves to be as much esteemed in this country as it is in ,ceylon1 for its optical properties are such that it is a very snappy stone4 ,some of the colors in which it occurs1 such as the golden browns1 lend themselves nicely to the matching of gems and garments1 and1 with the growth of education in such matters1 jewelers would do well to get better acquainted with the possibilities of zircon and to introduce it to their customers4 ,the supply from ,ceylon is sufficient to justify popularizing the stone4 ,small zircons are found in almost every heavy concentrate1 as1 for example1 in the concentrates of the diamond mines of ,south ,africa1 and in those of gold placers in many places4 ,the rough stones resemble rough diamonds in luster and are sometimes mistaken for diamonds4 ,,garnets4 ,garnets of various types are found widely distributed in nature4 ,perhaps the ,bohemian supply is best known1 having furnished a host of small stones which have usually been rose cut for cluster work or made into beads4 ,the ,bohemian garnets are of the pyrope or fire-red type4 ,relatively few large stones of sufficient transparency for cutting are produced in the ,bohemian mines4 ,the so-called ,cape rubies of the diamond mines of ,south ,africa are pyrope garnets and some large and fine ones are found4 ,the ,arizona rubies are pyrope garnets1 and while seldom of notable size1 some are of very fine color1 approaching deep rubies1 and the color remains attractive by artificial light4 ,almandite garnet1 the almandine of the jeweler is less abundant than pyrope1 when of gem quality4 ,ceylon furnishes some and ,india furnishes perhaps more4 ,brazil1 from its prolific gem gravels at ,minas ,novas1 supplies good almandite1 and smaller quantities are found in many different localities4 ,hessonite garnet1 the cinnamon stone or hyacinth 7incorrect7 of the trade1 comes mainly from ,ceylon4 ,andradite garnet1 of the variety known as demantoid1 from its diamond-like properties1 and which is usually sold under the misleading name olivine in the trade1 comes from the western slopes of the ,ural ,mountains4 ,,tourmaline4 ,gem tourmaline comes from ,ceylon1 from ,madagascar1 from the ,ural ,mountains1 from ,brazil1 from ,maine1 from ,connecticut1 and from ,california4 ,the ,ceylon tourmalines are mostly yellow or yellowish green1 sometimes fine olive-green4 ,those from the ,urals may be pink1 blue or green4 ,brazilian tourmalines are usually green1 but sometimes red4 ,in fact in many localities several colors of tourmaline are usually found together and it may be that a single crystal will be green in most of its length but red or pink tipped4 ,some crystals have a pink core and a green exterior4 ,the author has found both of the two latter types in the ,haddam1 ,conn41 tourmalines1 and on one occasion was surprised to get back a wine-colored tourmaline from a cutter to whom he had sent a green crystal4 ,there was but a thin shell of the green material on the outside of the crystal4 ,some of the ,madagascar tourmaline is of a fine brownish red1 almost as deep as a light garnet1 and much clearer than most garnet4 ,would it not be fitting on account of its occurrence in several localities in the ,united ,states1 for ,americans to use more tourmaline in their jewels8 ,the quality of some of the tourmalines of ,maine1 and of ,california especially1 is not excelled by tourmaline from any other locality4 ,some of the ,maine tourmaline is of a delightful1 slightly bluish-green tint that almost approaches emerald4 ,,kunzite4 ,spodumene1 of the variety kunzite1 comes from ,san ,diego ,county1 ,california4 ,,quartz ,,gems4 ,coming now to the quartz gems we find amethyst and citrine1 or golden quartz widely distributed so that only the localities that furnish the better grades of these stones need be mentioned4 ,siberia and ,uruguay furnish fine amethyst4 ,brazil also furnishes large quantities of very good quality4 ,,amethyst4 ,the chief charm of the ,siberian amethyst lies in its large red component1 which enables it to change from a deep grape-purple by daylight to a fine red by artificial light that is rich in red rays1 and poor in blue ones4 ,the paler types of amethysts that were once esteemed1 probably for lack of the rich deep variety1 become gray in appearance and much less lovely under artificial light4 ,india furnishes some amethysts1 and papers of fancy color stones containing native cut gems from ,ceylon1 frequently contain amethysts1 but ,brazil1 ,uruguay1 and ,siberia furnish the great bulk of the stones that are regarded as choice to-day4 ,,yellow ,,quartz4 ,citrine or golden quartz comes mainly from ,brazil4 ,the ,spanish topaz is sometimes the result of heating smoky quartz from ,cordova province in ,spain4 ,our own western mountains furnish considerable yellow and smoky quartz fit for cutting4 ,,rose ,,quartz4 ,rose quartz of the finest quality comes from ,south ,dakota4 ,bavaria1 the ,ural ,mountains1 and ,paris1 ,maine1 have also furnished it4 ,,agate4 ,agates of the finest types1 such as carnelian and sard1 come principally from ,brazil and from ,india4 ,,opal4 ,opals now come most largely from ,australia1 the ,hungarian mines yielding but few stones at present4 ,the fine black opals of ,new ,south ,wales are unsurpassed by any that have ever been found elsewhere4 ,mexico furnishes considerable opal1 and is notable for its fine fire opal or cherry opal4 ,,jade4 ,most of the jade of the variety nephrite that is obtained to-day comes from several of the provinces of ,china or from ,siberia or from ,turkestan4 ,a dark-green nephrite comes from ,new ,zealand4 ,jade of the jadeite variety1 which is harder than nephrite and more highly valued1 is rare4 ,the best specimens come from ,upper ,burmah4 ,it is also found in ,china and in ,tibet4 ,,peridot4 ,peridot1 and the brighter olivine or chrysolite1 while of the same mineral species1 do not seem to occur together4 ,the darker bottle-green specimens come from the ,island of ,st4 ,john in the ,red ,sea4 ,it is said that many of the finer peridots now available have been recut from old stones mined many years ago4 ,queensland supplies light-green chrysolite1 and ,arizona a yellowish-green variety4 ,light-green stones have been found near the ruby mines of ,upper ,burmah4 ,,moonstone4 ,moonstone comes mainly from ,ceylon4 ,the native cut specimens are sent here and recut1 as1 when native cut1 the direction of the grain is seldom correct to produce the moonlight effect in symmetrical fashion4 ,the native cutters apparently try to retain all the size and weight that is possible1 regardless of the effect4 ,,turquoise4 ,turquoise of the finest blue and most compact texture 7and hence least subject to color change7 comes from the province of ,khorasan in ,persia4 ,several of our western states supply turquoise of fair quality1 notably ,new ,mexico1 ,arizona1 ,nevada1 and ,california4 ,,lapis ,,lazuli4 ,lapis ,lazuli comes from ,afghanistan1 from ,siberia1 and from ,south ,america4 ,,malachite4 ,malachite is found in many copper mines1 but principally in those of the ,ural ,mountains4 ,,azurite4 ,azurite is found in the ,arizona mines and in ,chessy1 in ,france 7hence the name chessylite1 sometimes used instead of azurite74 99 99 99 99 99 ,,references4 ,students who wish to get a fuller account of the occurrence of precious stones should run through ,g4 ,f4 ,herbert-,smith's ,gem-,stones under the different varieties4 ,this work is the most recent authentic work of a strictly scientific character4 ,dr4 ,george ,f4 ,kunz's ,gems and ,precious ,stones of ,north ,america gives a detailed account of all the finds in ,north ,america up to the time of publication4 ,many of these are of course of little commercial importance4 ,the ,mineral ,resources of the ,united ,states contains annually a long account of the occurrences of gem materials in this country4 ,a separate pamphlet containing only the gem portion can be had gratis from the office of the ,united ,states ,geological ,survey1 ,washington1 ,d4 ,c4 ,,lesson ,,xxii ,,how ,,rough ,,precious ,,stones ,,are ,,cut ,,rough ,,precious ,,stones4 ,john ,ruskin1 who had the means to acquire some very fine natural specimens of gem material was of the opinion that man ought not to tamper with the wonderful crystals of nature1 but that rather they should be admired in the rough4 ,while one can understand ,ruskin's viewpoint1 nevertheless the art of man can make use of the optical properties of transparent minerals1 properties no less wonderful than those exhibited in crystallization1 and indeed intimately associated with the latter1 and1 by shaping the rough material in accordance with these optical properties1 greatly enhance the beauty of the gem4 ,no material illustrates the wonderful improvement that may be brought about by cutting and polishing better than diamond4 ,in the rough the diamond is less attractive in appearance than rock crystal4 ,g4 ,f4 ,herbert-,smith likens its appearance to that of soda crystals4 ,another author likens it to gum arabic4 ,the surface of the rough diamond is usually ridged by the overlapping of minute layers or strata of the material so that one cannot look into the clear interior any more than one can look into a bank1 through the prism-glass windows that are so much used to diffuse the light that enters by means of them4 ,being thus of a rough exterior the uncut diamond shows none of the snap and fire which are developed by proper cutting4 ,as the diamond perhaps shows more improvement on being cut than any other stone1 and as the art of cutting the diamond is distinct from that of cutting other precious stones1 both in the method of cutting and in the fact that the workers who cut diamonds cut no other precious stones1 it will be well to consider diamond cutting separately4 ,before discussing the methods by which the shaping and polishing are accomplished let us consider briefly the object that is in view in thus altering the shape and smoothing the surface of the rough material4 ,,how ,,cutting ,,increases ,,brilliancy4 ,primarily the object of cutting a diamond is to make it more brilliant4 ,so true is this that the usual form to which diamonds are cut has come to be called the brilliant4 ,the adjective has become a noun4 ,the increased brilliancy is due mainly to two effects3 ,first1 greatly increased reflection of light1 and second1 dispersion of light4 ,the reflection is partly external but principally internal4 ,taking up first the internal reflection which is responsible for most of the white brilliancy of the cut stone we must note that it is a fact that light that is passing through any transparent material will1 upon arriving at any polished surface1 either penetrate and emerge or else it will be reflected within the material1 depending upon the angle at which the light strikes the surface4 ,for each material there is a definite angle outside of which light that is passing as above described1 is totally reflected within the material4 ,illustration3 ,,fig4 #i4 ,,ab represents the back surface of a piece of diamond4 ,,cd is a line perpendicular to ,,ab4 ,angle ,,cde is about #bd degrees4 ,dotted line1 ,,fdh represents the course taken by a ray of light which is totally reflected at ,d in such fashion that angle ,,fda equals angle ,,hdb4 ,any light proceeding towards ,,ab but between ,e and ,c1 would fail to be totally reflected4 ,most of it would penetrate ,,ab4 ,,total ,,reflection4 ,for diamond this critical angle1 as it is called1 is very nearly #bd from a perpendicular to the surface4 ,if now1 we shape a diamond so that most of the light that enters it from the front falls upon the first back surface that it meets1 at an angle greater than #bd to a perpendicular to that surface1 the light will be totally reflected within the stone4 ,the angle at which it is reflected will be the same as that at which it meets the surface4 ,in other words the angles of incidence and of reflection are equal4 ,see ,fig4 #i for an illustration of this point4 ,,theory ,,of ,,the ,,brilliant4 ,in the usual brilliant much of the light that enters through the front surface is thus totally reflected from the first rear facet that it meets and then proceeds across the stone to be again totally reflected from the opposite side of the brilliant4 ,this time the light proceeds toward the top of the stone4 ,see ,fig4 #aj--7;,from ,g4 ,f4 ,herbert-,smith's ,gem-,stones74 ,the angles of the top of a brilliant are purposely made so flat that the up coming light fails to be totally reflected again and is allowed to emerge to dazzle the beholder4 ,in the better made brilliants the angle that the back slope makes with the plane of the girdle is very nearly #da and the top angle1 or angle of the front slope to the plane of the girdle is about #ce4 ,such well made brilliants when held up to a bright light appear almost black--that is1 they fail to pass any of the light through them 7except through the tiny culet1 which1 being parallel to the table above1 passes light that comes straight down to it74 ,illustration3 ,,fig4 #aj4--;,,course ,,of ,,the ,,rays ,,of ,,light ,,passing ,,through ,a ,,brilliant4 ,in other words1 instead of allowing the light to penetrate them1 well-made brilliants almost totally reflect it back toward its source1 that is1 toward the front of the stone4 ,the well-cut diamond is a very brilliant object1 viewed from the front4 ,we must now consider how the fire or prismatic color play is produced1 for it is even more upon the display of fire than upon its pure white brilliancy that the beauty of a diamond depends4 ,,cause ,,of ,,fire4 ,as we saw in ,lesson ,x4 7which it would be well to re-read at this time71 white light that changes its course from one transparent medium to another at any but a right angle to the surface involved1 is not only refracted 7as we saw in ,lesson ,,ii47 but is dispersed1 that is1 light of different colors is bent by differing amounts and thus we have a separation of the various colors4 ,if this takes place as the ray of light leaves the upper surface of a brilliant the observer upon whose eye the light falls will see either the red1 or the yellow1 or the blue1 as the case may be1 rather than the white light which entered the stone4 ,if instead1 the dispersion takes place as the light enters the brilliant the various colored rays thus produced will be totally reflected back to the observer 7slightly weakened by spreading1 as compared to the direct or unreflected spectra74 ,thus dispersion produces the fire in a brilliant4 ,other materials than diamond behave similarly1 but usually to a much smaller extent1 for few gem materials have so high a refractive power or so great a dispersive power as diamond4 ,having considered the theory of the brilliant we may now take up a study of the methods by which the exceedingly hard rough diamond is shaped and polished4 ,,cleaving ,,diamonds4 ,if the rough material is of poor shape1 or if it has conspicuous defects in it which prevent its being made into a single stone1 it is cleaved 7i4 e41 split along its grain74 ,hard as it is1 diamond splits readily in certain definite directions 7parallel to any of the triangular faces of the octahedral crystal74 ,the cleaver has to know the grain of rough diamonds from the external appearance1 even when the crystals1 as found1 are complicated modifications of the simple crystal form4 ,he can thus take advantage of the cleavage to speedily reduce the rough material in size and shape to suit the necessity of the case4 ,the cleaving is accomplished by making a nick or groove in the surface of the rough material at the proper point 7the stone being held by a tenacious wax1 in the end of a holder1 placed upright in a firm support74 ,a thin steel knife blade is then inserted in the nick and a sharp light blow struck upon the back of the knife blade4 ,the diamond then readily splits4 ,,cutting ,,diamonds4 ,the next step is to give the rough material a shape closely similar to that of the finished brilliant but rough and without facets4 ,this shaping or cutting as it is technically called1 is done by placing the rough stone in the end of a holder by means of a tough cement and then rotating holder and stone in a lathe-like machine4 ,another rough diamond 7sometimes a piece of bort1 unfit for cutting1 and sometimes a piece of material of good quality which it is necessary to reduce in size or alter in shape7 is cemented into another holder and held against the surface of the rotating diamond4 ,the holder is steadied against a firm support4 ,it now becomes a case of diamond cut diamond1 each stone wearing away the other and being worn away itself4 ,the cutting process is fairly rapid and it leaves the stone 7which is reversed to make the opposite side7 round in form and with a rounding top and cone-shaped back4 ,stones of fancy shape1 such as square1 or cushion shape1 have to be formed in part by hand rubbing or bruting as it is called4 ,the facets must now be polished onto the stone4 ,usually the workers who cut do not cleave or polish4 ,,polishing ,,diamonds4 ,the polisher fixes the cut stone firmly in a metallic holder called a dop1 which is cleverly designed to hold the stone with much of one side of it exposed4 ,the holder is then inverted so that the stone is beneath and a stout copper wire attached to the holder is then clamped firmly in a sort of movable vise4 ,the latter is then placed on the bench in such a position that the diamond rests upon the surface of a rapidly revolving horizontal iron wheel or lap as it is called4 ,the surface of the latter is charged with diamond dust1 that is1 diamond dust has been pushed into the metal surface which thus acts as a support to the dust4 ,the latter wears away the diamond1 producing a flat facet4 ,the lap is kept moistened with oil and from time to time fresh oil and diamond dust are applied4 ,a speed of about #b1jjj rotations per minute is used4 ,,facetting4 ,the making of the facets is rather slow work1 especially when1 as is usually the case in making the table the work has to be done against one of the hard points of the crystal4 ,great care has to be taken to place the stone so that the grain lies in a correct position1 for diamond cannot be polished against the grain1 nor even exactly with it1 but only obliquely across it4 ,this requirement1 as much as anything1 has prevented the use of machines in polishing diamonds4 ,the table is usually first polished on1 then the four top slopes1 dividing the top surface into quarters1 then each of the four ridges thus left1 is flattened1 making eight facets and finally #cb facets1 exclusive of the table1 are made upon the top of the brilliant4 ,the stone is then reversed and #bd facets1 and the culet1 polished on the back4 ,as each facet nears its proper shape the stone is placed upon a particularly smooth part of the lap and a slight vibratory motion given to the holder by the hand4 ,this smooths out any lines or grooves that may have formed because of inequalities of surface of the lap4 ,when completely facetted the brilliant is finished and requires only to be cleaned1 when it is ready for sale4 ,,lesson ,,xxiii ,,how ,,rough ,,precious ,,stones ,,are ,,cut ,,and ,,what ,,constitutes ,,good ,,make--,concluded ,,slitting ,,and ,,cleaving4 ,the cutting and polishing of precious stones other than diamond is a trade entirely distinct from diamond cutting4 ,the precious stone lapidary cuts every species of stone except diamond4 ,the methods used by different lapidaries vary somewhat in their details1 and there are many trade secrets which are more or less jealously guarded by their possessors1 but in general the methods used to reduce the rough materials to the finished gems are as follows3 ,first1 the rough material1 if of too large size1 or if very imperfect1 is slitted1 or1 if it possesses a pronounced cleavage1 it may be cleaved1 in order to reduce the size or to remove imperfect parts4 ,slitting is accomplished by means of a circular disc of thin metal which is hammered so that it will be flat and rotate truly1 and is then clamped between face plates1 much as an emery wheel is held4 ,the smooth edge of the circular disc is then charged with diamond dust and oil1 the diamond dust being bedded into the edge of the metal disc by the pressure of some hard1 fine-grained material1 such as chalcedony1 or rolled into the metal by the use of a rotating roller4 ,once charged1 and kept freely supplied with oil1 a slitting wheel will slice a considerable number of pieces of any precious stone less hard than diamond1 and will do so with considerable rapidity4 ,the wheel is1 of course1 rotated very rapidly for this purpose4 ,the cleaving of certain gem materials1 such as true topaz 7which splits perfectly across the prism1 parallel to its base7 is easily accomplished1 and it is done in much the same manner as the cleaving of diamond4 ,the feldspar gems1 such as moonstone1 amazonite1 and labradorite1 also cleave very smoothly in certain directions4 ,spodumene1 of which ,kunzite is a variety1 cleaves almost too easily to be durable4 ,most gem minerals1 however1 lack such perfect cleavage and when it is desired to remove imperfect parts1 or to reduce large pieces to smaller sizes1 these materials are slitted as above described4 ,,rubbing ,,down4 ,the material being of nearly the dimensions of the finished piece1 the next step is to rub it down1 as it is called1 to approximately the shape and size desired4 ,this rubbing down process was formerly done by means of a soft metal lap 7sometimes of lead71 charged with coarse emery powder and water4 ,carborundum1 being harder and sharper than emery1 has replaced it very largely4 ,some of the softer materials1 such1 for example1 as turquoise1 are rubbed down on a fast flying carborundum wheel of similar type to those used in machine shops for grinding steel tools4 ,these wheels rotate in a vertical plane and are kept wet4 ,the laps before mentioned run horizontally4 ,the carborundum wheels have the grains of carborundum cemented together by means of some binding material and this gradually crumbles1 exposing fresh1 sharp cutting edges4 ,various sizes of grain1 and various degrees of hardness of the binding material1 as well as various speeds1 are needed to suit the many different materials rubbed down by the lapidary4 ,some lapidaries rub down the harder and more valuable gems such as ruby upon diamond charged laps of brass or other metal4 ,,cabochons4 ,the rubbing down process does not leave a facetted surface1 but only a coarse roughly rounded or flattened surface4 ,if the material is to be left in some one of the flat-backed1 rounded top forms known as cabochon cut1 the surfaces need only to be smoothed 7by means of very fine abrasives such as fine emery applied by means of laps1 or even by fine emery or carborundum cloth71 and they are then ready for polishing4 ,,facetted ,,stones4 ,if1 however1 the stone is to be facetted in either the brilliant form1 somewhat like the diamond1 or step cut or otherwise facetted1 it is cemented strongly onto a holder 7much like the wooden part of a pen holder74 ,the upper end of the holder is rested in one of a series of holes in what is called a ginpeg resting in the work-bench near a metal lap1 and the stone is pressed upon the rapidly rotating surface of the lap1 which is charged with diamond dust or carborundum1 according to the hardness of the material to be facetted4 ,a flat facet is thus ground upon the stone4 ,by rotating the holder a series of facets1 all in the same set1 is produced4 ,the holder is then changed to a new position on the ginpeg and another set of facets laid upon the stone4 ,thus as many as four or five tiers or sets of facets may be applied to one side1 say the top of the stone4 ,the latter is then removed from the holder and cemented to it again1 this time with the bottom exposed1 and several sets of facets applied4 ,the stone is now cut but not polished4 ,the facets are flat1 but have a rough ground-glass like surface4 ,the polishing is usually done by workers who do not cut stones1 but who do nothing but polish them4 ,in small shops1 however1 the same lapidary performs all the parts of the work4 ,,polishing4 ,the polishing of stones1 whether cabochon or facetted1 is accomplished by the use of very finely powdered abrasives such as corundum powder1 tripoli1 pumice1 putty powder1 etc4 ,each gem material requires special treatment to obtain the best results4 ,it is here that most of the trade secrets apply4 ,the troubles of the lapidary in getting the keen polish that is so much admired on fine gems are many4 ,in general1 the polishing powder should not be quite as hard as the material to be polished1 else it may grind rather than polish4 ,the material should be used with water or oil to give it a creamy consistency4 ,it should be backed by laps of different materials for different purposes4 ,thus1 when backed by a fairly hard metal even tripoli1 although much softer1 will polish sapphire4 ,on a lap of wood1 tripoli would fail to polish hard materials1 but would polish amethyst or other quartz gem4 ,a change of speed of the lap1 too1 changes the effect of the polishing material4 ,i have seen a lapidary1 who was having no success at polishing an emerald1 get very good results by using a stick as a brake and slowing down his lap4 ,the polishing material must be of very uniform size1 preferably water floated or oil floated1 to give good results4 ,the lap must be kept flat and true and the stone must be properly held1 or the flatness of the facets1 upon which brilliancy depends in part1 will be destroyed during the polishing4 ,the softer materials1 such as opal1 require treatment more like that accorded cut glass1 and soft abrasive powders1 such as pumice1 suffice to polish them4 ,probably hardly two lapidaries would work exactly alike in their treatment of precious stones1 and each guards his secrets1 yet all use approximately similar general methods4 ,some have devised mechanical holders which permit the repeated cutting of stones to exactly the same angles1 and that1 too1 with an accurate knowledge of the angles used4 ,these angles can be definitely altered for different materials1 according to their refractive indices4 ,other lapidaries produce very fine results by purely hand methods4 ,these details have been gone into to give an idea of the methods of the lapidary and of the many variations in method4 ,in general1 however1 the slitting or cleaving1 the rubbing down to shape1 the smoothing out of all scratches and the facetting and polishing are done somewhat similarly by all lapidaries4 ,having now had a glimpse of the methods of the lapidaries1 let us briefly consider what constitutes good make in stones other than diamond4 ,,good ,,make ,,in ,,colored ,,stones4 ,brilliants1 cut from materials having smaller refractive indices than diamond1 7and this group includes nearly all stones other than diamonds7 should have steeper back angles and higher tops than the best diamond brilliants have4 ,a #ce-;degree top angle 7the angle between the slope of the top and the plane of the girdle is called the top angle7 and a #da-;degree back angle being about ideal for diamond1 other gem materials should have more nearly a #ci-;degree top angle and a #dd-;degree back angle to give the greatest possible brilliancy4 ,however1 in the case of colored gems such as ruby1 sapphire1 etc41 where the value depends even more largely upon the color than upon the brilliancy1 it is frequently necessary to cut the brilliant thicker or thinner than these proportions in order to deepen or to thin the color4 ,in general1 the thicker a stone of a given spread the deeper the color will be4 ,the color may also be deepened by giving to the stone a rounded contour1 both above and below the girdle1 and facetting it in steps instead of in the brilliant form4 ,increasing the number of steps also serves to slightly deepen the color1 as a larger number of reflections is thus obtained within the material1 the light thus has to travel a greater distance through the colored mass1 and more of the light1 of color other than that of the stone1 is absorbed4 ,,improving ,,color ,,by ,,proper ,,cutting4 ,in addition to the color improvement that can be brought about by changing the shape of the cut stone there are a number of gem materials whose color varies very greatly in different directions1 and this fact calls for skillful use in order to obtain the best possible results4 ,thus most tourmalines of deep color must be cut with the top or table1 of the finished stone1 on the side of the prismatic crystal rather than at right angles to the axis of the prism4 ,if cut the latter way they would be much too dense in color4 ,on the other hand1 most blue sapphires should be cut across the prism axis rather than the way that tourmalines should be cut4 ,to cut a sapphire with its table on the side of the prism would be likely to cause it to have a greenish cast because of the admixture of the unpleasing ordinary ray of yellowish tint with the blue of the stone as seen up and down the prism4 ,some ,australian sapphires are of a pronounced green when viewed across the axis of the crystal4 ,rubies if cut1 as was recommended for sapphires1 give a very pure and very deep red color1 but lack somewhat in the display of dichroism given by rubies that are cut with the table on the side of the crystal and parallel to its axis4 ,lapidaries need to know and to make use of such optical relations as these and jewelers might well inform themselves in such matters1 especially if they have1 or hope to acquire1 trade in very fine colored stones4 ,,effect ,,of ,,shape ,,on ,,brilliancy4 ,in actual practice it is common to find colored stones poorly cut for brilliancy1 especially central brilliancy1 and that1 too1 without the excuse of sacrifice of brilliancy in order to improve color4 ,the fault is usually due to too great a desire to save size and weight4 ,frequently a stone would have greater value if properly cut1 even at the expense of some size and weight4 ,when stones are cut too shallow1 as is frequently the case1 they are sure to leak light in the center and they are thus weak and less brilliant there than they would be if made smaller in diameter and with steeper back slopes approximating #dd degrees4 ,round stones1 if their angles are correct1 are more brilliant than stones of other contour such as square or cushion shape1 or navette or heart shape4 ,it can readily be seen that such odd-shaped stones can hardly have the same top and back angles at every part of their circumference4 ,if the angle from a corner of a square stone is correct then the angle from the middle of one side is obviously a little different4 ,small differences of angle make considerable differences in the brilliancy of cut stones4 ,the prevailing tendency to cut nearly all diamonds round depends largely upon the above facts4 ,in the case of colored stones1 however1 the added attractiveness which comes with odd or different contour more than makes up for the slight loss of brilliancy that may attend upon the shape selected4 ,such shapes as lend themselves to special designs in mountings also justify any little loss in brilliancy that accompanies the change in shape1 provided the proportions retained give a considerable amount of total reflection within the stone and thus light up most of the stone as seen from the front4 ,the test of the make of a color stone is its appearance4 ,if it lights up well over most of its surface and if the color is right1 one should not criticize the make as one would be justified in doing in the case of a diamond4 ,if1 however1 the effect is less attractive it would many times be advisable to measure the angles of the stone1 or its thickness and spread as compared with similar measurements on a stone of fine appearance4 ,frequently one will thus find the reason for the failure of the stone to perform as it might1 and recutting should be resorted to in such cases in order to get a smaller but more beautiful and hence more valuable stone4 ,,lesson ,,xxiv ,,forms ,,given ,,to ,,precious ,,stones ,while precious stones are cut to many different forms1 there are1 nevertheless1 but a few general types of cutting4 ,these may be classified as follows3 ,first1 the cabochon 7,fig4 #aa7 type of cutting2 second1 the old rose 7,fig4 #ab7 type of cutting2 third1 the brilliant 7,fig4 #ac72 fourth1 the step cutting 7,fig4 #ad74 ,,cabochons4 ,of these the first1 or cabochon cutting1 is probably the most ancient4 ,the term comes from a ,french word signifying a bald pate 7caboche1 from ,latin cabo1 a head74 ,the usual round cabochon cut closely resembles the top of a head in shape4 ,cabochon cut stones usually have a flat base1 but sometimes a slightly convex base is used1 especially in opals and in moonstones1 and some stones of very dense color are cut with a concave base to thin them and thus to reduce their color4 ,the contour of the base may be round1 or oval1 or square1 or cushion shape1 or heart shape or of any regular form4 ,the top is always smooth and rounding and unfacetted4 ,the relation of the height or thickness to the length or width may be varied to suit the size and shape of the rough piece or to suit one's ideas of symmetry1 provided the material be an opaque one1 such as turquoise or lapis lazuli4 ,if1 however1 the material is transparent the best results in the way of the return of light to the front1 and hence in the display of the color of the material1 are had if the thickness is about one half the spread4 ,illustration3 ,,fig4 #aa4--;,,cabochon ,,cutting4 ,this relation depends upon the refractive index of the material1 but as most color stones are of somewhat similar refractive indices1 the above proportions are sufficiently accurate for all4 ,the object in view is the securing of total reflection of as much light as possible from the flat polished back of the stone4 ,cabochon stones are sometimes set over foil or on polished gold to increase the reflection of light4 ,the path of a ray of light through a cabochon cut stone is closely similar to that through a rose cut diamond see cut 7c7 of ,fig4 #ab for the latter4 ,like the rose cut1 the cabochon cut does not give much brilliancy as compared to the brilliant cut4 ,cabochon cut stones1 however1 have a quiet beauty of color which commends them to people of quiet taste1 and even fine rubies1 sapphires1 and emeralds are increasingly cut cabochon to satisfy the growing demand for fine taste in jewels4 ,the ,east ,indian has all along preferred the cabochon cut for color stones1 but possibly his motives have not been unmixed1 as the cabochon cut saves a greater proportion of the weight of the rough stone than the more modern types of cutting4 ,garnets1 more than other stones1 have been used in the cabochon cut1 and when in that form are usually known as carbuncles 7from carbunculus1 a glowing coal74 ,any other fiery red stone might equally well be styled a carbuncle1 especially if cabochon cut4 ,illustration3 ,,fig4 #ab4--,,rose ,,cutting4 ,scientific rubies look very well in the cabochon cut4 ,fig4 #aa shows in 7a7 and 7b7 the front and top of the usual round cabochon4 ,cut 7c7 of the same figure gives the front elevation of a cabochon which will light up better than the usual round-topped design4 ,in the round-topped type the central part of the top is so nearly parallel to the back that light can pass right through as through a window pane4 ,if the sloping sides are brought up to a blunt point1 as in cut 7c7 there is very much less loss of light and greater beauty results4 ,the ,east ,indian cabochons are frequently cut in a fashion resembling that suggested4 ,illustration3 ,,fig4 #ac4--;,,brilliant ,,cutting4 ,,rose ,,cut ,,stones4 ,it was natural that the earliest cut stones should have the simple rounded lines of the cabochon cutting1 for the first thing that would occur to the primitive worker who aspired to improve upon nature's product1 would be the rubbing down of sharp edges and the polishing of the whole surface of the stone4 ,perhaps the next improvement was the polishing of flat facets upon the rounded top of a cabochon stone4 ,this process gives us the ancient type of cutting known as the rose cut4 ,the drawings 7a7 and 7b7 of ,fig4 #ab show the front elevation and the top and 7c7 shows the path of a ray of light through a rose4 ,it will be noted that the general shape resembles that of a round cabochon1 but twenty-four triangular facets have been formed upon the top4 ,the well-proportioned rose has a thickness about one half as great as its diameter4 ,diamonds were formerly cut chiefly in the rose form1 especially in the days of the ,east ,indian mines1 and even in the early part of the nineteenth century many people preferred finely made roses to the thick1 clumsy brilliants of that day4 ,to-day only very small pieces of diamond are cut to roses4 ,as the material so used frequently results from the cleaving of larger diamonds1 the public has come to know these tiny roses as chips4 ,the best roses have twenty-four regular facets but small ones frequently receive only twelve1 and those are seldom regular in shape and in arrangement4 ,such roses serve well enough for encrusting watch cases and for similar work1 as the flat base of the stone can be set in thin metal without difficulty4 ,about the only gem other than diamond that is now cut to the rose form is garnet4 ,large numbers of small ,bohemian garnets are cut to crude rose form for use in cluster work4 ,illustration3 ,,fig4 #ad4--,,step ,,cutting4 ,,the ,,brilliant ,,cut1 as its name implies1 gives the most complete return of light of any of the forms of cutting4 ,the theory of the brilliant has already been discussed 7,lesson ,,xxii4 in connection with the cutting of diamond74 ,the shape of the brilliant is too well known to require much description4 ,most brilliants to-day are cut practically round and the form is that of two truncated cones placed base to base4 ,the upper cone is truncated more than the lower1 thus forming the large1 flat top facet known as the table of the stone ,a1 ,fig4 #ac1 cut 7a74 ,the truncating of the lower cone forms the tiny facet known as the culet1 which lies opposite to the table and is parallel to the latter see ,b1 ,fig4 #ac1 cut 7a74 ,the edge of meeting of the two cones is the girdle of the brilliant ,,cd in cut 7a71 ,fig4 #ac4 ,the sloping surface of the upper cone is facetted with thirty-two facets in the full cut brilliant1 while the lower cone receives twenty-four4 ,small stones sometimes receive fewer facets1 to lessen the cost and difficulty of cutting1 but by paying sufficient for them full cut brilliants as small as one hundred to the carat may be had4 ,cut 7b7 of ,fig4 #ac shows the proper arrangement of the top facets and cut 7c7 that of the bottom facets4 ,when cutting colored stones in the brilliant cut1 especially if the material is very costly and its color in need of being darkened or lightened1 the lapidary frequently takes liberties with the regular arrangement and proportions depicted in the cuts4 ,,step ,,cutting4 ,the only remaining type of cutting that is in very general use is the step cut 7sometimes known as trap cut74 ,fig4 #ad1 7a71 7b71 and 7c71 shows the front elevation1 the top and the back of a square antique step cut stone4 ,the contour may be round or completely square or oblong or of some other shape1 just as a brilliant may have any of these contours4 ,the distinctive feature of the step cutting is the several series of parallel-edged quadrangular facets above and below the girdle and the generally rounding character of its cross section4 ,this plump1 rounding character permits the saving of weight of the rough material1 and by massing the color gives usually a greater depth of color than a brilliant of the same spread would have if cut from similar material4 ,while probably never quite as snappy and brilliant as the regular brilliant cut1 a well-proportioned step cut stone can be very brilliant4 ,many fine diamonds have recently been cut in steps for use in exclusive jewelry4 ,,the ,,mixed ,,cut4 ,the ruby and the emerald are never better in color than when in the full step cut1 although rubies are frequently cut in what is known as the mixed cut1 consisting of a brilliant cut top and a step cut back4 ,sapphires and many other colored stones are commonly cut in the mixed cut4 ,recently it has become common to polish the tops of colored stones with a smooth unfacetted1 slightly convex surface1 the back being facetted in either the brilliant or the step arrangement4 ,such stones are said to have a buffed top4 ,they are less expensive to cut than fully facetted stones and do not have the snappy brilliancy of the latter4 ,they do1 however1 show off the intrinsic color of the material very well4 ,,lesson ,,xxv ,,imitations ,,of ,,precious ,,stones ,,paste ,,gems4 ,large volumes have been written on paste jewels1 especially on antique pastes4 ,contrary to a prevailing belief1 the paste gem is not a recent invention4 ,people frequently say when told that their gems are false1 ,but it is a very old piece1 it must be genuine4 ,the great age of a jewel should rather lead to suspicion that it was not genuine than give confidence that a true gem was assured4 ,the ,egyptians and ,romans were skillful makers of glass of the sort used in imitating gems and some of the old pastes were very hard or else have become so with age4 ,glass of one variety or another makes the most convincing sort of imitation precious stones4 ,the term paste as applied to glass imitations is said to come from the ,italian pasta meaning dough1 and it suggests the softness of the material4 ,most pastes are mainly lead glass4 ,as we saw in ,lesson ,,xviii41 on the chemical composition of the gems1 many of them are silicates of metals4 ,now glasses are also silicates of various metals1 but unlike gem minerals the glasses are not crystalline but rather amorphous1 that is1 without definite geometric form or definite internal arrangement4 ,the optical properties of the various glasses vary chiefly with their densities1 and the denser the material the higher the refractive index and the greater the dispersion4 ,thus to get the best results in imitation stones they should be made of very heavy glass4 ,the dense flint glass 7chiefly a silicate of potassium and lead7 which is used for cut glass ware illustrates admirably the optical properties of the heavy glasses4 ,by using even more lead a still denser glass may be had1 with even a greater brilliancy4 ,unfortunately the addition of lead or other heavy metals 7such as thallium7 makes the product very soft and also very subject to attack by gases such as are always present in the atmosphere of cities4 ,this softness causes the stones to scratch readily so that when worn they soon lose their polish and with the loss of polish they lose their beauty4 ,the attack of the gases before mentioned darkens the surfaces of the imitation and further dulls it4 ,when fresh and new a well cut piece of colorless paste has a snap and fire that approaches that of diamond4 ,the surface luster is not adamantine1 however1 and the edges of the facets cannot be polished so sharply as those on a diamond4 ,moreover the refractive index1 while high1 is never so high as in a diamond and hence the brilliant cannot be so shaped as to secure the amount of total reflection given by a well-made diamond4 ,hence1 the paste brilliant1 while quite satisfying as seen from squarely in front1 is weak and dark in the center as seen when tilted to one side4 ,by these differences the trained eye can detect paste imitations of diamond at a glance without recourse to tests of specific gravity1 hardness1 etc4 ,pastes1 being amorphous1 are singly refracting1 as is diamond4 ,this fact helps the appearance of the paste brilliant1 for light does not divide within it to become weakened in power4 ,this singleness of refraction1 however1 betrays the paste imitation when it is colored to resemble ruby1 sapphire or emerald1 all of which are doubly refracting4 ,the color is imparted to pastes by the addition1 during their manufacture1 of various metallic oxides in small proportions4 ,thus cobalt gives a blue color1 copper or chromium green1 copper or gold give red 7under proper treatment7 and manganese gives purple4 ,by experiment the makers of pastes have become very skillful in imitating the color of almost any precious stone4 ,fine paste emeralds may look better than inferior genuine emeralds4 ,as pastes are singly refracting and hence lack dichroism1 the pleasing variety of color of the true ruby cannot be had in a paste imitation1 but the public is not critical enough to notice this lack4 ,the expert would1 however1 note it and could detect the imitation by that difference as well as by the lack of double refraction4 ,the use of direct sunlight and a white card as already explained in the lesson on double refraction 7,lesson ,,iii47 will serve to expose the singleness of refraction of paste imitations4 ,spinels and garnets are about the only true gems 7except diamond7 that are single refracting4 ,any other color stone should show double refraction when tested by the sunlight-card method4 ,the file test will also expose any paste imitation as all the very brilliant pastes are fairly soft4 ,,doublets4 ,to give better wearing quality to paste imitations the doublet was devised4 ,this name is used because the product is in two parts1 a lower or back portion of paste and an upper or top portion of some cheap but hard genuine stone4 ,garnet is probably used for this purpose to a greater extent than any other material1 although quartz or colorless topaz will do very well4 ,the usual arrangement of the parts can be seen in ,fig4 #ae1 the garnet covering only a part of the upper surface1 namely the table part and a small portion of the sloping surface of the top4 ,in high class doublets the hard mineral covers the paste to the girdle4 7,see ,fig4 #af47 ,the color of the garnet does not interfere seriously with that of the paste4 ,illustration3 ,,fig4 #ae4 ,,one ,,form ,,of ,,cheap ,,doublet4 ,if a diamond doublet is desired the slice of garnet is made nearly as thin as paper and it covers only the table of the brilliant4 ,it is thus practically colorless4 ,a thin slice of red garnet over a green background is not noticeable1 as all the red is absorbed in passing through the green material beneath4 ,with a blue base1 the red upper layer may give a very slight purple effect4 ,with yellow a slight orange tint results and of course with a red back no perceptible difference would result4 ,illustration3 ,,fig4 #af4 ,,another ,,form ,,of ,,doublet4 ,the two materials are cemented together1 by means of a transparent waterproof cement4 ,the triplet has already been described in ,lesson ,,xii4 ,it is even better than the doublet and more difficult to detect4 ,both the file test and the sunlight-card test serve to detect doublets1 as well as paste imitations1 except that in the file test with the fully protected doublet the back of the stone must be tested with the file1 as the girdle and top are of hard material4 ,in the sunlight-card test of a doublet 7the refraction of garnet being single like that of glass71 single images of the facets will be had on the card when the sunlight is reflected onto it4 ,a reflection of the lower or inner surface of the garnet top can be seen also and this serves to still further identify a doublet or a triplet4 ,the appearance of this reflection is much like that received on the card from the top of the table4 ,it is larger than the reflections of the smaller facets and is but little colored4 ,,tests ,,for ,,doublets4 ,a trained eye can also detect a doublet or a triplet by noting the difference in the character of the surface luster of the garnet part and of the glass part4 ,garnet takes a keener and more resinous luster than glass4 ,by tipping the doublet so that light is reflected to the eye from the sloping top surface1 one can see at once where the garnet leaves off and the glass begins4 ,even through a show window one can tell a doublet in this way although here it is necessary to move oneself1 instead of the stone1 until a proper position is obtained to get a reflection from the top slope of the doublet4 ,if the garnet covers the whole top of the imitation then it is not possible to get so direct a comparison1 but even here one can look first at the top surface and then at the back and thus compare the luster4 ,it is also well to closely examine with a lens the region of the girdle1 to see if any evidence of the joining of two materials can be seen4 ,frequently the lapidary bevels the edge so as to bring the line of junction between real and false material at the sharp edge of the bevel4 ,boiling a doublet in alcohol or chloroform will frequently dissolve the cement and separate the parts4 ,the dichroscope also serves to detect the false character of doublets and paste imitations1 as neither shows dichroism4 ,as rubies1 emeralds1 sapphires1 and in fact most colored stones of value1 show distinct dichroism1 this test is a sure one against these imitations4 ,triplets and doublets too may be exposed by dipping them sidewise into oil1 thus removing the prismatic refraction almost completely1 as the oil has about the same refractive index as the stone4 ,one can then look directly through glass and garnet1 or other topping material1 separately1 and each material then shows its proper color4 ,thus zones of color appear in a doublet or triplet when under the oil4 ,a real gem would appear almost uniform in color under these conditions4 ,round gas bubbles can frequently be found in paste1 and hence in the paste part of a doublet4 ,also1 the natural flaws of the real stone are never found in paste1 but may be present in the real stone part of a doublet or a triplet4 ,some imitation emeralds on the market1 however1 have been made in a way to counterfeit the flaws and faults generally found in this stone4 ,,altered ,,stones4 ,in addition to the out and out imitations made of paste1 and the doublets1 there are numerous imitations current in the trade that are made by staining or by otherwise altering the color of some genuine but inexpensive gem material4 ,for example1 large quantities of somewhat porous chalcedony from ,brazil are stained and sold in imitation of natural agate or sard or other stones4 ,in many cases the staining is superficial1 so that the stone has to be shaped before it is stained1 then stained and polished4 ,large quantities of slightly crackled quartz are stained to resemble lapis lazuli1 and sold1 usually with the title ,swiss ,lapis4 ,a file test will reveal the character of this imitation1 as it is harder than a file1 while true lapis is softer4 ,the color too is never of so fine a blue as that of fine lapis4 ,it has a ,prussian blue effect4 ,turquoises of inferior color are also sometimes stained to improve them4 ,a better product is made artificially4 ,opals are sometimes impregnated with organic matter1 which is then charred1 perhaps with sulphuric acid1 thus giving them somewhat the appearance of black opal4 ,opals are also imitated by adding oxide of tin to glass1 thus imparting a slight milkiness to it4 ,the imitation is then shaped from this glass by molding1 and the back of the cabochon is given an irregular surface1 which may be set over tinsel to give the effect of fire4 ,pale stones are frequently mounted over foil1 or in enameled or stained settings and thus their color is seemingly improved4 ,diamonds of poor color are occasionally painted2 often the back of the brilliant is treated with a violet dyestuff1 which even in so small an amount that it is difficult to detect1 will neutralize the yellow of the stone and make it appear to be of a fine blue-white color4 ,the painting is1 of course1 not permanent1 so that such treatment of a diamond with a view to selling it is fraudulent4 ,the painted stone may be detected by washing it with alcohol1 when the dye will be removed and the off-color will become apparent4 ,if the stone is unset one can see with a lens a wavery metallic appearance on the surfaces that have been painted4 ,this effect is due to the action of the very thin film of dye upon the light that falls upon it4 ,besides the staining of genuine materials1 they are sometimes altered in color by heat treatment1 and this topic will be discussed in the next lesson4 ,,lesson ,,xxvi ,,alteration ,,of ,,the ,,color ,,of ,,precious ,,stones ,many gem minerals change color when more or less strongly heated4 ,extreme heat whitens many colored materials completely4 ,,pinked ,,topaz4 ,john ,ruskin advises us to seek out and cast aside all manner of false or dyed or altered stones but1 in spite of his advice1 perhaps the most justifiable use of heat treatment is that which alters the color of true topaz from a wine-yellow to a fine pink4 ,it would appear that the wine-yellow is a composite color composed of pink and yellow and that the pink constituent is less easily changed by heat than is the yellow one4 ,if too high a temperature is used both colors disappear and white topaz results4 ,as the latter is abundant in nature and of little value1 such a result is very undesirable4 ,pink topaz1 however1 is very rare1 and until recently1 when pink tourmaline from ,california and ,madagascar1 and pink beryl 7morganite7 from ,madagascar1 became available in quantity1 the pinked topazes had but few competing gems1 and thus commanded a higher price than the natural topazes4 ,of course1 care has to be taken in heating a mineral to raise and lower the temperature slowly1 in order to avoid sudden and unequal expansion or contraction1 which would crack and ruin the specimen1 as the writer learned to his sorrow with the first topaz that he tried to pink4 ,,spanish ,,topaz4 ,another material that gains a more valuable color by heat treatment is the smoky quartz of ,spain1 which1 on being gently heated1 yields the so-called ,spanish topaz4 ,some amethysts are altered to a yellow color by mild heating4 ,too great a temperature completely decolorizes colored quartz4 ,some dark quartz yields a nearly garnet red product1 after heating4 ,,zircon4 ,slight increase in temperature causes many of the zircons from ,ceylon to change markedly in color4 ,an alcohol flame serves admirably to effect the change1 care being taken to warm up the stone very gradually and to cool it slowly4 ,drafts should be prevented1 as they might suddenly cool the stone and crack it4 ,some zircons become completely whitened by this treatment4 ,at the same time they increase markedly in density and in refractive index and thus become even more snappy and brilliant than when colored4 ,one is tempted to suspect that the space lattice of the crystal has had its strata drawn closer together during the heating and left permanently in a closer order of arrangement4 ,other zircons merely become lighter colored and less attractive4 ,some of the whitened stones again become more or less colored on exposure to strong light4 ,ultra-violet light will sometimes restore these to a fine deep color in a short time4 ,the whitened zircon1 when finely cut in the brilliant form1 with truly flat facets and sharp edges and with a top angle of about #ci degrees and a back angle of about #dd degrees1 so closely resembles a diamond that it will deceive almost anyone on casual inspection4 ,the expert1 even1 may be deceived1 if caught off his guard4 ,the writer has a fine specimen of a little over one carat1 with which he has deceived many jewelers and pawnbrokers1 and even an importer or two4 ,if it is presented as a stone that closely resembles diamond your expert will say3 ,yes1 it is pretty good1 but it would never fool me4 ,if1 however1 you catch him off his guard by suggesting1 perhaps1 ,did you ever see a diamond with a polished girdle81 then he will look at it with interest1 remark on its fine color and make1 and never think of challenging its character4 ,the refractive index of the dense type of zircon is so high 7#a4ib-a4ih7 that it lights up well over most of the surface of the brilliant when cut1 as above indicated1 and does not show markedly the weak dark center shown by white sapphire1 white topaz1 colorless quartz1 colorless beryl1 and paste1 when seen from the side4 ,moreover1 the luster of zircon is nearly adamantine1 so the expert does not miss the cold metallic glitter as he would with any other white stone4 ,the color dispersion1 too1 is so high 7#hf as great as in diamond7 that the zircon has considerable fire1 and thus the casual handler is again deceived4 ,a fine white zircon is really prettier than a poor diamond4 ,it cannot compare1 however1 with a fine diamond4 ,it would never do to let an expert see your zircon beside even a fair diamond4 ,the zircon would look sleepy4 ,it is only when no direct comparison is possible1 and when the expert is not suspicious1 that a zircon can deceive him4 ,of course1 the use of the scientific tests of the earlier lessons will1 at once1 detect the character of a whitened zircon4 ,the hardness is but #g4e1 the refraction so strongly double that the edges of the back facets appear double-lined when viewed through the table with a lens1 and the specific gravity is #d4fi4 ,double spots of light appear on the card when the sunlight-card test is applied4 ,hence1 it is easy to detect zircon by any of these tests if there is reason to suspect that it has been substituted for diamond4 ,,corundum ,,gems4 ,rubies of streaky color are said to be improved by careful heating4 ,usually ruby undergoes a series of color changes on being heated1 but returns through the same series in reverse order on being cooled1 and finally resumes its original color4 ,strong heating will whiten some yellow sapphire4 ,the author thus obtained a white sapphire from a crystal of light yellow material4 ,it is interesting to note that the corundum gems undergo marked change in color under the influence of radium4 ,a regular series of changes is said to be produced in white sapphire by this means1 the final color being yellow4 ,this color may then be removed by heat and the series run through again4 ,it is not stated that a fine red has ever been thus obtained4 ,perhaps ,nature1 by her slower methods1 using the faint traces of radio-active material in the rocks1 reddens the corundum of ,burmah at her leisure1 and finally arrives at the much sought pigeon blood color4 ,it is said that the natives of ,india have a legend to the effect that the white sapphires of the mines are ripening rubies1 and that one day they will mature4 ,perhaps they are not far wrong4 ,,diamond4 ,diamonds of yellowish tint may be improved in color by the use of high-power radium4 ,at present the latter is so rare and costly that there is no evidence of its commercial use for this purpose4 ,scientists have brought about the change to a light blue as an experiment4 ,it is not yet known whether the change will be permanent4 ,perhaps here again ,nature has anticipated man's discovery and made the fine bluish-violet ,brazilian diamonds 7which fluoresce to a deep violet under an arc light1 and which shine for a few moments in the dark after exposure to light7 by associating them for ages with radio-active material4 ,some of the ,african stones also have these characteristics4 ,aside from the change in the color of diamond that may be brought about by means of radium1 the mineral is extremely reluctant to alter its color4 ,many experimenters besides the author have tried in vain a host of expedients in the hope of finding some way to improve the color of diamond4 ,about the only noticeable alteration that the author has been able to bring about was upon a brown diamond1 the color of which was made somewhat lighter and more ashen by heating it in a current of hydrogen gas to a low red heat4 ,,lesson ,,xxvii ,,pearls ,unlike the gems that have been so far considered1 the pearl is not a mineral1 but is of organic origin1 that is1 it is the product of a living organism4 ,there are two principal types of molluscs which yield true pearls in commercial quantities4 ,the best known of the first type is the so-called pearl oyster 7,meleagrina margaritifera74 ,the pearl mussel of fresh water streams is of the second type 7,unio margaritifera74 ,other species of molluscs having pearly linings to their shells may produce pearls1 but most of the pearls of commerce come from one or the other of the two varieties mentioned4 ,,structure ,,of ,,pearl4 ,the structure and material of the true pearl must be first understood in order to understand the underlying reasons for the remarkable beauty of this gem4 ,pearls are composed partly of the mineral substance calcium carbonate 7chemically the same as marble7 and partly of a tough1 horny substance of organic nature called conchiolin4 ,the shell of the pearl-bearing mollusc is also composed of these two substances4 ,calcium carbonate may crystallize in either of two forms1 calcite or aragonite4 ,in marble we have calcite4 ,in the outer portions of the shell of the pearl oyster the calcium carbonate is in the form of calcite1 but in the inner nacreous lining and in the pearl itself the mineral is present as aragonite4 ,this is deposited by the mollusc in very thin crystalline layers in the horny layers of conchiolin1 so that the lining of the shell is built of approximately parallel layers of mineral and of animal substance4 ,in the normal shell this is all that takes place1 but in the case of a mollusc whose interior is invaded by any small source of irritation1 such as a borer1 or a grain of sand1 or other bit of foreign material1 a process of alternate deposit of conchiolin and of aragonite goes on upon the invading matter1 thus forming a pearl4 ,the pearl is built in layers like an onion4 ,in shape it may be spherical1 or pear-shaped1 or button-shaped or of any less regular shape than these4 ,the regular shapes are more highly valued4 ,the spherical shape is of greatest value1 other things being equal4 ,next comes the drop or pear shape1 then the button shape1 and after these the host of irregular shapes known to the jeweler as baroques4 ,the river man who gathers mussels calls these odd-shaped pearls slugs4 ,let us now attempt to understand how the beautiful luster and iridescence of the pearl are related to the layer-like structure of the gem4 ,in the first place1 it should be understood that both conchiolin and aragonite are translucent1 that is1 they pass light to a certain extent4 ,the layers being exceedingly thin1 light can penetrate a considerable number of them if not otherwise deflected from its course4 ,we thus obtain reflections not merely from the outer surface of a pearl1 but from layer after layer within the gem and all these reflections reach the eye in a blended reflection of great beauty4 ,the luster of a pearl is then not purely a surface luster in the usual sense of that term1 but it is a luster due to many superposed surfaces4 ,it is so different from other types of luster that we describe it merely as pearly luster even though we find it in some other material1 as1 for example in certain sapphires1 in which it is due to a similar layer-like arrangement of structure4 ,,orient4 ,the fineness of the luster of a pearl1 or as is said in the trade1 the orient1 depends upon the number of layers that take part in the reflection1 and this number in turn depends upon the translucency of the material and the thinness of the layers4 ,very fine pearls usually have very many1 very thin layers taking part in the reflection4 ,the degree of translucency1 considered apart1 is sometimes called the water of the pearl4 ,in addition to their beautiful luster1 many pearls display iridescence1 and this is due in part1 as in the case of the pearly lining of the shell 7mother of pearl7 to overlapping of successive layers1 like the overlapping of shingles on a roof4 ,this gives rise to a lined surface1 much like the diffraction grating of the physicist1 which is made by ruling a glass plate with thousands of parallel lines to the inch4 ,such a grating produces wonderful spectra1 in which the rainbow colors are widely separated and very vivid4 ,the principal on which this separation of light depends is known as diffraction and cannot be explained here1 but a similar effect takes place when light falls on the naturally ruled surface of a pearl and helps produce the play of colors known as iridescence4 ,the thin layers themselves also help to produce the iridescence by interference of light much as in the case of the opal1 which has already been discussed4 ,,color4 ,having explained the cause of the orient and water of pearls1 the color must next be considered4 ,pearls may be had of almost any color1 but the majority of fine pearls are white1 or nearly so4 ,the fine ,oriental pearls frequently have a creamy tint4 ,among fresh water pearls the creamy tint is less often seen1 but fine pink tints occur4 ,occasionally a black pearl is found and on account of its rarity commands a price nearly as great as that obtainable for a white pearl of similar size and quality4 ,the value of pearls depends upon several different factors and it is far from an easy matter to estimate the value of a fine specimen4 ,it is much easier to grade and estimate the value of diamonds than to do the same for pearls1 and it is only by long and intimate acquaintance with the pearls themselves that one can hope to become expert in deciding values4 ,there are1 however1 several general factors that govern the value of pearls4 ,chief among these are3 #a1 ,orient2 #b1 ,color2 #c1 ,texture or ,skin2 #d1 ,shape and ,size4 ,,factors ,,governing ,,the ,,value ,,of ,,pearls4 ,taking up each of these factors in turn1 it may be said of the first that unless a pearl has that fine keen luster known as a fine orient1 it is of but limited value4 ,no matter what the size1 or how perfect the shape1 it is nothing1 if dead and lusterless4 ,to have great value the gem must gleam with that soft but lively luster peculiar to fine specimens of pearl4 ,with variations in orient go wide variations in value4 ,as to color1 the choicest pearls are pure white or delicate rose pink or creamy white4 ,pearls in these shades can be had in numbers and these colors are what might be called regular colors4 ,fancy-colored pearls have peculiar and irregular values1 depending a good deal upon rarity and upon the obtaining of a customer for an odd color4 ,fine pink and fine black pearls are examples of the type that is meant here4 ,to be very valuable a pearl must have a smooth even skin1 that is1 the texture of its surface must be even and regular4 ,it must not have pits or scratches or wrinkles1 or little raised spots upon it1 or any cracks in it4 ,in connection with this topic of skin1 it may be mentioned that it is sometimes true that a pearl of bad skin or of poor luster may be improved markedly by peeling it1 as the process is called4 ,as was said above1 a pearl is built in layers much like an onion1 and it can often be peeled1 that is1 one or more layers can be removed1 thus exposing fresh layers beneath1 whose texture and luster may be better than those of the original outside layer4 ,,peeling ,a ,,pearl4 ,possibly an anecdote of an actual case may serve best to explain the method by which peeling is sometimes accomplished4 ,the writer was once at ,vincennes1 ,ind41 on business1 and there became acquainted with a pearl buyer who was stopping at that place to buy fresh water pearls and slugs from the rivermen who gather the mussels for the sake of their shells4 ,the latter are made into pearl buttons for clothing4 ,it happened that the pearl buyer had accumulated some twenty-eight ounces of slugs and a number of pearls and was leaving on the same train with the author1 who shared his seat with him4 ,while we were looking over the slugs together the pearl buyer put his hand in his pocket and drew out a five-dollar bill which he unrolled1 exposing a pearl of about six grains1 well shaped1 but of rather dead luster4 ,remarking that he had paid but #d for it and that he had rolled it up in the bill for safe keeping until he got time to peel it1 he took out a small penknife1 opened one of the blades1 put a couple of kid glove finger tips on the thumb and first finger of his left hand and proceeded to peel the pearl on the moving train4 ,holding his two hands together to steady them1 he pressed the edge of his knife blade against the pearl until the harder steel had penetrated straight down through one layer4 ,then with a flaking1 lateral motion he flaked off a part of the outer skin4 ,bit by bit all of the outer layer was flaked off1 and that1 too1 without appreciably scratching the next layer1 so great was the worker's skill4 ,when the pearl was completely peeled it was gently rubbed with three grades of polishing paper1 each finer than the previous one1 and then the writer was allowed to examine it4 ,the appearance had been much improved1 although it was not of extremely fine quality even when peeled4 ,under a high power magnifier scarcely a trace of the peeling could be seen4 ,the value of the #d pearl had been raised to at least #ajj and not many minutes had been required for the change4 ,a slower and more laborious1 but safer1 process of peeling a pearl1 consists in gently rubbing the surface with a very fine1 rather soft1 abrasive powder until all of the outer skin has been thus worn away4 ,of course1 in many such cases no better skin than the outer one could be found and disappointment would result from the peeling of such a pearl4 ,it should be added that it will not do to try to peel a part of a pearl in order to remove an excrescence1 for then one would inevitably cut across the layers1 exposing their edges1 and such a surface looks1 when polished1 much like a pearl button1 but not like a pearl4 ,in this connection may be mentioned the widespread belief on the part of the public that the concretions found in the common edible oyster can be polished by a lapidary1 as a rough precious stone can be improved by the latter1 and that a fine pearl will result4 ,it is frequently necessary for jewelers to whom such pearls are brought1 to undeceive the person bringing them and to tell him that only those molluscs that have a beautiful pearly lining to their shells are capable of producing true pearls and that the latter require no assistance from the lapidary4 ,,shape4 ,to return to the topic of factors governing the value of pearls1 the shape of the pearl makes a vast difference in the value4 ,perfectly spherical pearls are most highly valued and closely following come those of drop or pear shape1 as this shape lends itself nicely to the making of pendants4 ,oval or egg-shaped pearls are also good4 ,after these come the button shapes1 in which one side is flattened4 ,pearls of irregular shape are much less highly valued4 ,the irregular-shaped pearls are called baroque pearls in the trade4 ,the rivermen engaged in the fresh water pearl fishery call them slugs4 ,some of the more regular of these are called nuggets4 ,others are termed spikes because of their pointed shape1 and still others are called wing pearls on account of their resemblance to a bird's wing4 ,most of the baroques are too irregular in shape to have any special name applying to their form4 ,,weight4 ,after orient1 color1 skin1 and shape have been considered1 size or weight finally determines the value4 ,pearls are sold by an arbitrary unit of weight known as the pearl grain4 ,it is not equal to the grain avoirdupois1 but is one fourth of a diamond carat4 ,as the new metric carat is one fifth of a gram and as there are #ae4dc avoirdupois grains in a gram1 it is seen at once that there are but #c4jh real grains in a carat rather than four4 ,thus the pearl grain is slightly lighter than the avoirdupois grain4 ,since large1 fine pearls are exceedingly rare1 the value mounts with size much more rapidly than is the case with any other gem2 in fact1 the value increases as the square of the weight4 ,for example1 let us consider two pearls1 one of one grain weight1 the other of two grains1 and both of the same grade as to quality4 ,if the smaller is worth say #b per grain1 then the larger is worth #b #b 7the square of the weight7 times #b 7the price per grain base1 as it is called in the trade71 which totals #h4 ,a four-grain pearl of this grade would be worth #d #d #b #cb1 etc4 ,thus it is seen that the price increases very rapidly with increase in weight4 ,,price ,,per ,,grain ,,base4 ,some of the lower grades of pearls in small sizes are sold by the grain straight1 that is1 the price per grain is merely multiplied by the weight in grains to get the value1 just as the price per carat would be multiplied by the number of carats to get the value of a diamond4 ,this method of figuring the value of pearls is used only for the cheaper grades and small sizes1 however1 and the method first explained1 the calculation per grain base1 is the one in universal use for fine gems4 ,very fine exceptional gems may be sold at a large price for the piece1 regardless of the weight4 ,it is interesting to note in this connection that ,tavernier1 the ,french gem merchant of the seventeenth century1 tells us that in his day the price of large diamonds was calculated by a method similar to that which we now use for pearls1 that is1 the weight in carats was squared and the product multiplied by the price per carat4 ,such a method would give far too high a price for diamonds to-day4 ,,the ,,high ,,price ,,of ,,fine ,,pearls4 ,this suggests the thought that pearls of fine quality and great size are the most costly of all gems to-day and yet there seems to be no halting in the demand for them4 ,in fact1 ,america is only just beginning to get interested in pearls and is coming to esteem them as they have long been esteemed in the ,east and in ,europe4 ,those who have thought that the advance in the prices of diamonds in recent years will soon put them at prohibitive rates should consider the enormous prices that have been obtained and are being obtained for fine pearls4 ,in order to facilitate the calculating of prices of pearls1 tables have been computed and published giving the values of pearls of all sizes at different prices per grain base1 and several times these tables have been outgrown1 and new ones1 running to higher values1 have been made4 ,the present tables run to #ej per grain base4 ,there is much justification for the high prices demanded and paid for large and fine pearls4 ,such gems are really exceedingly scarce4 ,those who1 as boys1 have opened hundreds of river mussels only to find a very few small1 badly misshapen slugs will realize that it is only one mollusc in a very large number that contains a fine pearl4 ,moreover1 like the bison and the wild pigeon1 the pearl-bearing molluscs may be greatly diminished in numbers or even exterminated by the greed of man and his fearfully destructive methods of harvesting nature's productions4 ,in fact1 the fisheries have been dwindling in yield for some time1 and most of the fine pearls that are marketed are old pearls1 already drilled1 from the treasuries of ,eastern potentates1 who have been forced by necessity to accept the high prices offered by the ,west for part of their treasures4 ,in ,india1 pearls have long been acceptable collateral for loans1 and many fine gems have come on the market after failure of the owners to repay such loans4 ,having considered the factors bearing on the value of pearls1 we will next consider briefly their physical properties4 ,the specific gravity is less definite than with minerals and varies between #b4fe and #b4gj4 ,it may be even higher for pink pearls4 ,,physical ,,properties4 ,in hardness pearls also vary1 ranging between #c-a_/b and #d on ,mohs's scale4 ,they are thus very soft and easily worn or scratched by hard usage4 ,a case showing the rather rapid wearing away of pearls recently came to the attention of the writer4 ,a pendant in the shape of a ,latin cross had been made of round pearls which had been drilled and strung on two slender gold rods to form the cross4 ,the pearls were free to rotate on the wires4 ,after a period of some twenty or more years of wear the pearls had all become distinctly cylindrical in shape1 the rubbing against the garments over which the pendant had been worn having been sufficient to grind away the soft material to that extent4 ,the luster was still good1 the pearls having virtually been peeled very slowly by abrasion4 ,,care ,,of ,,pearls4 ,this example suggests the great care that should be taken by owners of fine pearls to prevent undue rubbing or wear of these valuable but not extremely durable gems4 ,they should be carefully wiped after being worn to remove dust and then put away in a tightly closed case4 ,pearls should never be allowed to come in contact with any acid1 not even weak acids like lemonade1 or punch or vinegar1 as1 being largely calcium carbonate they are very easily acted upon by acids1 and a mere touch with an acid might ruin the surface luster4 ,being partly organic in nature1 pearls are not everlasting1 but must eventually decay1 as is shown by the powdery condition of very old pearls that have been found with mummies or in ancient ruins4 ,the organic matter has yielded to bacterial attack and decayed1 leaving only the powdery mineral matter behind4 ,as heat and moisture are the conditions most conducive to the growth of bacteria1 and hence to decay1 it would follow that fine pearls should be kept in a dry cool place when not in use4 ,,lesson ,,xxviii ,,cultured ,,pearls ,,and ,,imitations ,,of ,,pearls ,,cultured ,,pearls4 ,like all very valuable gems1 pearls have stimulated the ingenuity of man to attempt to make imitations that would pass for genuine4 ,perhaps the most ingenious1 as well as the most natural looking product1 is the cultured pearl4 ,this is really natural pearl on much of its exterior1 but artificial within and at the back4 ,in order to bring about this result the ,japanese1 who originated the present commercial product1 but who probably borrowed the original idea from the ,chinese1 call to their assistance the pearl oyster itself4 ,the oysters are gently opened1 small hemispherical discs of mother-of-pearl are introduced between shell and mantle and the oyster replanted4 ,the foreign material is coated by the oyster with true pearly layers as usual1 and after several years a sufficiently thick accumulation of pearly layers is thus deposited on the nucleus so that the oyster may be gathered and opened and the cultured pearl removed by sawing it out from the shell to which it has become attached4 ,to the base is then neatly cemented a piece of mother-of-pearl to complete a nearly spherical shape1 and the portions of the surface that have not been covered with true pearl are then polished4 ,the product1 when set in a proper pearl mounting1 is quite convincing and really beautiful4 ,as the time during which the oyster is allowed to work upon the cultured pearl is doubtless far less than is required for the growth of a large natural pearl1 the number of layers of true pearly material is considerably smaller than the number of layers that take part in the multiple reflections explained in the previous lesson1 and hence the orient of the cultured pearl is never equal to that of a fine true pearl4 ,it is frequently very good however1 and for uses that do not demand exposure of the whole surface of the pearl1 the cultured pearl supplies a substitute for genuine pearls of moderate quality and price4 ,the back parts of the cultured pearl1 being only polished mother-of-pearl1 have the appearance of the ordinary pearl button1 rather than that of true pearl4 ,,imitations ,,of ,,pearls4 ,aside from these half artificial cultured pearls1 the out and out imitations of pearls that have been most successfully sold are of two general types1 first ,roman pearls1 and1 second1 ,indestructible pearls4 ,the ,roman pearls are made hollow and afterward wax filled1 the ,indestructible pearls have solid enamel bases4 ,in both types the pearly appearance is obtained by lining the interior1 or coating the exterior1 with more or less numerous layers of what is known as nacre or some times as essence d'oriente4 ,this is prepared from the scales of a small fish found in the ,north ,sea and in ,russia4 ,the scales are removed and treated with certain solutions which remove the silvery powder from the scales4 ,the nacre is then prepared from this powder4 ,the fineness of the pearly effect becomes greater as the preparation ages1 so very fine imitations are usually made from old nacre4 ,the effect is also better the larger the number of successive layers used4 ,the artificial pearl thus resembles the true pearl in the physical causes for the beautiful effect4 ,in some cases the ,roman pearl has a true iridescence which is produced by burning colors into the hollow enamel bead4 ,some of the indestructible pearls are made over beads of opalescent glass1 thus imparting a finer effect to the finished product4 ,while the cheaper grades of indestructible pearls have but three or four layers of nacre1 some of the fine ones have as many as thirty or more4 ,the earlier indestructible pearls were made with a coating material which was easily affected by heat1 or by water1 or by perspiration1 as a gelatine-like sizing was included in it4 ,the more recent product has a mineral binder which is not thus affected1 so that the pearls are really about as durable as natural ones1 and will at least last a lifetime if used with proper care4 ,like fine natural pearls1 the fine imitations should be wiped after use and carefully put away4 ,they should also be restrung occasionally1 as should real pearls both to prevent loss by the breaking of the string and because the string becomes soiled after a time1 and this hurts the appearance of the jewel4 ,the ,roman type of imitation will not stand much heat1 as the wax core would melt and run out4 ,,testing ,,imitations ,,of ,,pearls4 ,as the making of imitations of pearls is mainly hand-work and as many treatments are required for the best imitations1 fairly high prices are demanded for these better products1 and the appearance and permanency warrant such prices4 ,the best imitation pearls are really very difficult of detection except by close examination4 ,they will not1 of course1 stand inspection under a high magnification4 ,artificial pearls may also be detected by their incorrect specific gravity1 by their incorrect degree of hardness1 and in the case of the hollow pearls by making a tiny ink spot upon the surface of the pearl and looking at it through a lens4 ,a reflection of the spot from the inside surface of the bead will appear beside the spot itself if the pearl is of the ,roman type4 ,the artificial pearls so far described are high class products4 ,some of the very cheap and poor imitations are merely solid1 or hollow1 glass or enamel beads which have been made slightly pearly1 either by adding various materials to the glass or enamel when it was made1 or by crudely coating the beads without or within with wax containing cheap nacre4 ,,lesson ,,xxix ,,the ,,use ,,of ,,balances ,,and ,,the ,,unit ,,of ,,weight ,,in ,,use ,,for ,,precious ,,stones ,as precious stones are almost always sold by weight1 and as the value at stake is frequently very great1 it is almost as necessary for a gem merchant1 as it is for the chemist1 to have delicate balances and to keep them in good order and to use them skillfully4 ,a general understanding of the unit of weight in use for precious stones and how it is related to other standard weights is also necessary to the gem dealer4 ,we will therefore consider in this lesson the use and care of balances and the nature and relative value of the unit of weight for precious stones4 ,,delicate ,,balances ,,needed4 ,as it is necessary1 on account of their great value1 to weigh some gems1 such as diamonds1 emeralds1 rubies1 etc41 with accuracy to at least the one hundredth part of a carat 7which is roughly in the neighborhood of #a_/ae1jjj of an ounce avoirdupois71 balances of very delicate and accurate construction are a necessary part of the equipment of every gem merchant4 ,while portable balances of a fair degree of accuracy are to be had1 the best and surest balances are substantially constructed and housed in glass cases1 much as are those of the analytic chemist1 which must do even finer weighing4 ,the case protects the balance from dust and dirt and prevents the action of air currents during the weighing4 ,the balance itself has very delicate knife edges1 sometimes of agate1 sometimes of hardened steel1 and these knife edges rest1 when in use1 on a block of agate or steel1 so that there is a minimum amount of friction4 ,when not in use the balance beam and knife edges are lifted from the block and held firmly by a metal arm1 or else1 as is the case with some balances1 the post supporting the block is lowered1 leaving the beam and knife edges out of contact with it4 ,the object of this separation is to prevent any rough contact between the knife edges and the block on which they rest4 ,advantage should always be taken of this device whenever any fairly heavy load is put on or taken off of either pan1 as the sudden tipping of the beam might chip the knife edges if not supported4 ,when the load is nearly balanced there may be no harm in carefully adding or removing small weights while the knife edges are resting on the block1 but even then it is safer to lower the beam and pans4 ,it should be needless to state that as level and rigid a support should be had for one's balance as circumstances permit4 ,,method ,,of ,,use ,,of ,,balances4 ,before using a balance one should see that the pans are clean1 that the base of the balance is properly leveled 7the better balances have a spirit level attached7 and that the pans balance each other without load4 ,when slightly out of balance the defect may be adjusted by unscrewing the little adjusting nut at the end of the beam that is too light1 or by screwing in the nut at the opposite end4 ,having seen that the adjustment is perfect the pans should be lowered and the object to be weighed placed on the left-hand pan 7because a right-handed person will find it handier to handle his weights on the right-hand pan74 ,one should next guess as nearly as possible the weight of the stone and place well back on the right-hand pan the weight that he thinks comes nearest to that of the stone4 ,if the weight is too heavy the next lighter weight should replace it4 ,smaller weights should be added until a perfect balance is had1 the small weights being neatly arranged in the order of their size1 in order to more rapidly count them when the stone is balanced4 ,this is the case when the pointer swings approximately equal distances to the right and to the left and there is then no need to wait for it to come to rest in the center4 ,it is well to count the weights as they lie on the pan 7which is easily done if they have been arranged in descending order of size as suggested above7 then write down the total1 and on removing the weights count aloud as they are replaced in the box and note if the total checks that which was written down4 ,it may seem unnecessary to be so careful in this matter1 but it is better to be over-careful than to make a mistake where every hundredth of a carat may mean from one to five or six dollars or more4 ,no dealer can afford to have a stone that he has sold prove to be lighter than he has stated it to be4 ,one should be at least within one one-hundredth of a carat of the correct weight4 ,it should be unnecessary to add that accurate weights should never be handled with the fingers4 ,ivory tipped forceps are best for handling the weights4 ,the forceps commonly used for handling diamonds will1 in time1 wear away the weights by scratching them so that they will weigh materially less4 ,unless the weights are of platinum or plated with gold1 the perspiration of the hands would cause them to oxidize and gain in weight4 ,it would be well to discard the smaller weights1 which are most in use1 every few years and obtain new and accurate ones4 ,in case this is not done one should at least have the weights checked against others known to be of standard weight4 ,any chemist will have balances and weights far more accurate than the best in use for precious stones and will gladly check the weights of a gem dealer for a moderate fee4 ,to check the accuracy of your balance1 change the stone and weights to opposite pans1 in which case they should still balance4 ,one should never overload a balance1 both because the balance might be injured and because the relative accuracy decreases as the load increases4 ,if the weight of a parcel of stones heavier than the total of the weights provided with the balance is desired1 the parcel should be divided and weighed in parts4 ,while many dealers neglect some of the precautions above suggested and somehow get along1 yet it is safer to use care and to have correct technique in the handling of one's balances4 ,having indicated a few of the refinements of method in weighing we will next consider the unit of weight in use for precious stones and see how it is related to other units of weight and in what manner it is subdivided4 ,,the ,,unit ,,of ,,weight ,,for ,,precious ,,stones4 ,the present unit for precious stones in the ,united ,states is the metric carat4 ,most of the more progressive countries have in recent years agreed upon the use of this unit4 ,its use in the ,united ,states became general ,july #a1 #aiac4 ,it is by definition exactly one fifth of a gram 7the unit of weight of the ,metric ,system of weights and measures74 ,its relation to the grain is that there are #c4jh grains in the metric carat4 ,the carat in use in this country up to a few years ago was about #b-a_/b heavier than the present metric carat4 ,it was equal to 4#bjec grams instead of 4#bjjj grams 7#a_/e gram74 ,the carats of countries not using the metric carat vary considerably1 but yet approximate the metric carat somewhat nearly4 ,thus1 that in use in ,great ,britain was 4#bjec g41 in ,amsterdam 4#bjeg g41 in ,berlin 4#bjedd g41 in ,lisbon 4#bjege g41 and in ,florence #j4aigb g4 ,the latter was the only one that was under the metric carat4 ,the change to the metric carat was desirable1 as it unified the practice of weighing1 which not only varied in different countries1 but even in the same country4 ,thus there was no very exact agreement among the makers of diamond weights in the ,united ,states prior to the adoption of the metric carat4 ,one man's carat was a bit heavier or lighter than another's4 ,with a definite and simple relationship to the standard gram there is now no excuse for any variation in weights4 ,the ,bureau of ,standards at ,washington affords manufacturers every facility for standardizing their weights4 ,,the ,,decimal ,,system ,,of ,,subdivision ,,of ,,the ,,carat4 ,with the adoption of the metric carat the custom of expressing parts of a carat in common fractions whose denominators were powers of the number #b 7#a_/b1 #a_/d1 #a_/h1 #a_/af1 #a_/cb1 #a_/fd7 was discarded as awkward and slow for computation and the decimal system of subdivision was adopted4 ,thus the metric carat is divided into tenths and one hundredths4 ,it is customary1 however1 to sum up the one hundredths and express them as the total number of one hundredths and not to express them as tenths4 ,thus1 a stone of #b4eg carats is said to weigh two and fifty-seven hundredths carats4 ,the decimal system of subdivision of the carat makes the figuring of values simpler where no tables are handy4 ,of course1 new tables were at once prepared when the new carat was adopted and they afford a rapid means of ascertaining the value of a stone of any weight when the price per carat is known4 ,should it become necessary to convert the weight of a stone from its expression in the old system to that of the new1 one need only get #a4jb-a_/b of the old weight4 7,the old carat was approximately 4#bje g41 while the new one is 4#bjj g4 ,hence one old carat 4#bje 4#ajb-a_/b is ---- -------- #ajb-a_/b of a new one47 4#bjj 4#ajj ,,method ,,of ,,converting ,,weights4 ,if the old weight has fractions these should first be changed to decimals for convenience4 ,for example1 suppose it is wished to change #b-a_/d #a_/af old carats to metric carats4 #a_/d 4#be and #a_/af 4#jfbe4 ,hence #b-a_/d #a_/af #b4cabe4 ,now get #ajb-a_/b of this3 7#b4cabe #a4jbe #b4cg metric carats74 ,if1 for any reason one should need to change from metric carats to old ,u4 ,s4 carats one should multiply by 4#igef 7 4#bjj g4 7 7 ------- 4#igef 7 7 4#bje g4 7 ,as was said in ,lesson ,,xxv41 pearls are sold by the pearl grain1 which is arbitrarily fixed at #a_/d of a carat4 ,with the change to the metric carat the pearl grain was correspondingly changed and its weight is now #a_/d of 4#bjj g4 4#je g41 as expressed in the metric system4 ,,lesson ,,xxx ,,tariff ,,laws ,,on ,,precious ,,and ,,imitation ,,stones ,since it is necessary for a nation1 as well as for an individual1 to have an income1 and since articles of luxury are more easily taxed than are those of necessity1 the traffic in gems and their imitations has frequently been made a source of revenue to our government4 ,usually the per cent4 charged as tariff has been comparatively low1 especially upon very valuable gems1 such as diamonds and pearls1 for the reason that too high a tariff would tend to tempt unscrupulous dealers to smuggle such goods into the country without declaring them4 ,when the margin of difference between the values1 with and without the tariff1 is kept small the temptation is but slight1 when the danger of detection and the drastic nature of the usual punishment are taken into account4 ,rough stones have frequently been allowed to enter the country duty free because they were regarded as desirable raw materials which would afford employment to home industry4 ,the tariff laws of ,october #c1 #aiac1 made1 however1 some sweeping changes in the policy of our government toward precious stones and as those laws are still in force 7,april #d1 #aiag7 this lesson will attempt to set forth clearly the exact conditions under the present law4 ,perhaps the paragraph of first importance to the trade is ,no4 #ceg which reads as follows4 #ceg4 ,diamonds and other precious stones1 rough or uncut1 and not advanced in condition or value from their natural state by cleaving1 splitting1 cutting1 or other process1 whether in their natural form or broken1 and bort2 any of the foregoing not set1 and diamond dust1 #aj per centum ad valorem2 pearls and parts thereof1 drilled or undrilled1 but not set or strung2 diamonds1 coral1 rubies1 cameos1 and other precious stones and semi-precious stones1 cut but not set1 and suitable for use in the manufacture of jewelry1 #bj per centum ad valorem2 imitation precious stones1 including pearls and parts thereof1 for use in the manufacture of jewelry1 doublets1 artificial1 or so-called synthetic or reconstructed1 pearls and parts thereof1 rubies1 or other precious stones1 #bj per centum ad valorem4 ,it will be noticed that the chief changes over the previous law are first that which imposes a #aj duty on rough precious stones1 which were formerly free of duty1 and second the advance in the duty on cut diamonds and other cut stones from the former #aj to the present #bj4 ,this increase in the tariff was regarded as unwise by many conservative importers1 as the temptation to defraud the government is made much greater than before4 ,the change was even feared by honest dealers who were afraid that they could not successfully compete with dishonest importers who might smuggle gems into the country4 ,in spite of a rather determined opposition the change was made and our most representative dealers have been making the best of the situation and have been doing all that they could to help prevent smuggling or at least reduce it to a minimum4 ,through their knowledge of the movements of diamond stocks and of prices they are able to detect any unduly large supply or any unwarranted lowness of price and thus to assist the government agents by directing investigation towards any dealer who seems to be enjoying immunity from the tariff4 ,the question of the status of ,japanese cultured pearls has been settled as follows4 ,paragraph #ceg 7quoted above7 is ruled to cover them and they are thus subject to a #bj ad valorem tax4 ,carbonadoes--miners' diamonds--are free of duty1 under paragraph #dgd4 ,crude minerals are also free of duty1 paragraph #edi4 ,paragraph #fjg declares ,specimens of natural history and mineralogy are free4 ,in case the owner is not prepared to pay the tax on imported merchandise the government holds the goods for a period of three years pending such payments4 ,in case an importer shows that imported merchandise was purchased at more than actual market value1 he may deduct the difference at time of entry and pay duty only on the wholesale foreign market value1 under ,section ,,iii41 paragraph #a4 ,on the other hand1 if the examiner finds merchandise to be undervalued on the invoice1 such merchandise is subject to additional penal duties1 but in case of disagreement between the importer and the examiner as to the actual market value1 appeal may be taken to the ,customs ,court4 ,since the ,philippine ,islands are possessions of the ,united ,states1 pearls from those islands may be admitted free of duty when the facts of their origin are certified to4 ,in the case of precious stones which had their origin in the ,united ,states1 but which were exported and kept for a time abroad it has been ruled that such stones may be imported into the ,united ,states free of duty4 ,when precious or imitation precious stones are imported into the ,united ,states and subsequently mounted into jewelry which is then exported1 the duty which was paid upon entry may be refunded less a deduction of #a4 ,the author wishes to extend his thanks to ,examiner ,w4 ,b4 ,treadwell of ,new ,york1 for his assistance in regard to the subject dealt with in this lesson4 ,,bibliography ,the student of gems will1 of course1 want to read many books on the subject and the following brief bibliography will enable the beginner to select his reading wisely from the start4 ,much more complete bibliographies will be found in some of the books listed here1 one which is notably complete to date of publication is contained in ,diamonds and ,precious ,stones1 by ,harry ,emanuel1 ,f4,r4,g4,s41 ,london1 ,john ,camden ,hotten1 #ahfg4 ,this covers many languages4 ,the book which will probably be found most useful by those who have mastered this little text is the work by ,g4 ,f4 ,herbert-,smith1 to which frequent reference has been made at the close of many of our chapters4 ,it is thoroughly scientific1 yet understandable1 and is very complete on the scientific side of the subject4 ,gem-,stones1 ,g4 ,f4 ,herbert-,smith1 ,jas4 ,pott ,co41 ,n4 ,y4 ,for another work and one which contains information of trade character as well as scientific information about gems see ,precious ,stones by ,w4 ,r4 ,cattelle1 ,j4 ,b4 ,lippincott ,co41 ,phila41 or see ,a ,handbook of ,precious ,stones1 by ,m4 ,d4 ,rothschild1 ,g4 ,p4 ,putnam's ,sons1 ,n4 ,y4 ,gems and ,gem ,minerals1 by ,oliver ,cummings ,farrington1 ,a4 ,w4 ,mumford1 publisher1 ,chicago1 #aijc1 is another good general work on gems4 ,its color plates of rough gem minerals are especially good4 ,those who are especially interested in the diamond should see ,the ,diamond by ,w4 ,r4 ,cattelle1 ,the ,john ,lane ,co41 ,n4 ,y41 which gives a good account of its subject and is rich in commercial information1 or ,diamonds3 ,a ,study of the ,factors which ,govern their ,value1 by the present author1 ,g4 ,p4 ,putnam's ,sons1 ,n4 ,y41 #aiad4 ,sir ,wm4 ,crook's1 the ,diamond1 ,harper ,bros41 ,n4 ,y41 is very interesting1 especially in its account of the author's visits to the ,s4 ,african mines4 ,students of pearls will find ,the ,book of the ,pearl1 by ,dr4 ,geo4 ,f4 ,kunz and ,dr4 ,chas4 ,stevenson1 ,century ,co41 ,n4 ,y41 very complete4 ,a smaller work1 yet a good one1 on pearls is ,the ,pearl by ,w4 ,r4 ,cattelle1 ,j4 ,b4 ,lippincott ,co41 ,phila41 #aijg4 ,this book is strong on the commercial side4 ,an older work is ,pearls and ,pearling by ,d4 ,edwin ,streeter1 ,geo4 ,bell ,co41 ,london4 ,a work on gems and gem-cutting by a practical cutter is ,the ,gem ,cutter's ,craft1 by ,leopold ,claremont1 ,geo4 ,bell ,sons1 ,london1 but it should be said that very few trade secrets will be found exposed in the book4 ,on the subject of scientific precious stones ,the ,production and ,identification of ,artificial ,precious ,stones1 by ,noel ,heaton1 ,b4,sc41 ,f4,c4,s41 read before the ,royal ,society of ,arts1 ,apr4 #bf1 #aiaa1 is very fine4 ,it may be had in the annual ,report of the ,smithsonian ,institution for #aiaa1 p4 #bag4 ,it gives one of the best accounts to be had of the history of the artificial production of precious stones1 especially of the corundum gems4 ,it also contains a splendid account of how to distinguish scientific from natural gems4 ,most students of gems will need to refer frequently to some good text-book of mineralogy4 ,although old1 ,dana's ,mineralogy is still a standard work4 ,a newer book and one of a more popular nature is ,l4 ,p4 ,gratacap's ,the ,popular ,guide to ,minerals1 ,d4 ,van ,nostrand ,co41 ,n4 ,y4 ,among larger and more expensive books on gems may be mentioned ,precious ,stones1 by ,dr4 ,max ,bauer4 ,this is an ,english translation of a ,german work which is a classic in its field4 ,as it is now out of print in its ,english edition1 a somewhat detailed account of its character may be of value to those who may be inclined to go to the effort to seek a copy at a public library or perhaps to purchase one through second-hand book stores4 ,a popular account of their characters1 occurrence and applications1 with an introduction to their determination1 for mineralogists1 lapidaries1 jewelers1 etc41 with an appendix on pearls and coral1 by ,dr4 ,max ,bauer1 ,privy ,councillor1 professor in the ,union of ,marburg4 ,translated from the ,german by ,l4 ,j4 ,spencer1 ,m4,a4 7,cantab471 ,f4,g4,s41 assistant in the mineral department of the ,british ,museum4 ,with twenty plates and ninety-four figures in the text4 ,london1 ,chas4 ,griffin ,co41 ,ltd43 ,phila41 ,j4 ,b4 ,lippincott ,co41 #aijd4 ,the book is a large one1 xv #fbg pages1 and is divided into three parts with an appendix on pearls and coral4 ,part ,i4 deals with the general characters of precious stones4 #a4 ,natural characters and occurrence4 #b4 ,applications of ,precious ,stones4 #c4 ,classification of ,precious ,stones4 #ajf pages4 ,part ,,ii4 ,systematic ,description of ,precious ,stones1 ,diamond1 ,corundum ,gems1 ,spinel1 etc4 #dej pages4 ,part ,,iii4 ,determination and ,distinguishing of ,precious ,stones4 #bj pages4 ,appendix1 #bf pages4 ,pearls and ,coral4 ,bauer is exhaustive in his descriptions of the more important precious stones and he also describes briefly very many little known and little used gem minerals4 ,on forms of cutting he is old-fashioned4 ,first #fh pages given to explanation of characters used in identifying stones4 ,good4 ,on the ,process of ,cutting4 ,pages #gi-hg4 ,good account4 ,more practical than most books give4 ,careful accounts of occurrence of precious stones with maps4 ,character of the occurrence of diamond in ,india1 ,brazil1 and ,africa1 quite in detail4 ,the student who wishes to master the subject of gems cannot afford to neglect ,bauer4 ,for those who read ,french1 the latest1 the most complete and thorough book on gems is ,jean ,escard's ,les ,pierres ,prcieuses1 ,h4 ,dunod et ,e4 ,pinat1 ,paris1 #aiad4 ,it is a large and finely illustrated work4 ,the author has really outdone ,bauer4 ,the detail in regard to diamonds especially is very fine4 ,even the use of diamonds in mechanical ways is very completely gone into and also details in regard to cutting diamonds are very completely given4 ,it is to be hoped that an ,english translation will soon become available4 ,another large and thoroughgoing work is ,gardner ,f4 ,williams' ,the ,diamond ,mines of ,south ,africa1 ,mac,millan1 ,n4 ,y4 ,dr4 ,geo4 ,f4 ,kunz's ,gems and ,precious ,stones of ,north ,america1 ,the ,sci4 ,pub4 ,co41 ,n4 ,y41 #ahij1 #ccf pages1 #h colored plates 7excellent ones too71 many engravings1 is a very complete account of all published finds of precious stones in the ,united ,states1 ,canada1 and ,mexico1 giving a popular description of their value1 history1 archeology1 and of the collections in which they exist1 also a chapter on pearls and on remarkable foreign gems owned in the ,united ,states4 ,many rare and little known semi-precious stones are described here4 ,dr4 ,kunz is also the author of several more recent gem books notably ,the ,magic of ,jewels and ,charms and ,the ,curious ,lore of ,precious ,stones1 ,lippincott1 ,phila4 ,among books on engraved gems is the old ,hand ,book of ,gem ,engraving by ,c4 ,w4 ,king2 ,bell ,daldy1 ,london1 #ahff1 and one by ,duffield ,osborne2 ,henry ,holt ,co41 ,n4 ,y4 ,another book on this subject is ,engraved ,gems by ,maxwell ,somerville2 ,drexel ,biddle1 ,phila4 ,for those who wish still further references the following older works will prove interesting4 ,precious ,stones1 by ,w4 ,r4 ,cattelle2 ,lippincott1 ,phila4 ,precious ,stones1 by ,w4 ,goodchild2 ,d4 ,van ,nostrand ,co41 ,n4 ,y4 ,julius ,wodiska1 of ,new ,york1 has also written an interesting work on precious stones1 ,a ,book of ,precious ,stones1 ,putnam's1 #aijg4 ,still older works are ,precious ,stones and ,gems by ,edwin ,w4 ,streeter2 ,chapman ,hall1 ,london1 #ahgg4 ,this is a book of #bfd pages with nine illustrations4 ,it contains much of value and was unsurpassed in its day4 ,its first-hand accounts of numerous important1 even celebrated diamonds and other precious stones will always make it valuable to the student of gems4 ,another book by the same author is ,the ,great ,diamonds of the ,world2 ,geo4 ,bell ,sons1 ,london1 #ahhb2 #cba pages4 ,not illustrated4 ,its title adequately describes its contents4 ,it is an excellent work4 ,the author even traveled in ,india tracing the history of some of the famous diamonds that he describes4 ,diamonds and ,precious ,stones1 by ,louis ,dieulafait published in its ,english translation by ,scribner1 ,armstrong ,co41 ,n4 ,y41 #ahgd1 is another old but interesting work4 ,it has #bib pages and #abf engravings on wood4 ,it gives a fine account of diamond cutting as practiced at that time4 ,there is also an excellent history of the production of artificial precious stones to that date4 ,the ,natural ,history of ,precious ,stones and of the ,precious ,metals by ,c4 ,w4 ,king1 ,m4,a41 ,bell ,daldy1 ,london1 #ahgj1 is rich in references to classical literature4 ,one or two interesting monographs on precious stones have been written and ,the ,tourmaline1 by ,augustus ,c4 ,hamlin is one of these4 ,mr4 ,hamlin became interested in gems because of his accidental discovery of some of the fine tourmalines of ,maine4 ,his ,leisure ,hours among the ,gems is also very readable4 ,jas4 ,r4 ,osgood ,co41 ,boston1 #ahhd4 ,it deals especially with diamond1 emerald1 opal1 and sapphire4 ,he gives a good account of ,american finds of diamond1 and a long account of ,european regalia4 ,the book is full of interesting comment and contains many references to older authors4 ,the ,tears of the ,heliades or ,amber as a ,gem1 by ,w4 ,arnold ,buffum1 ,g4 ,p4 ,putnam's ,sons1 ,n4 ,y41 #aijj1 is as its name implies a monograph on amber4 ,a good work on the history of precious stones and on historical-jewels is ,gems and ,jewels by ,madame de ,barrera2 ,richard ,bentley1 ,london1 #ahfj4 ,it deals also with the geography of gem sources4 ,an interesting chapter on ,great ,jewel ,robberies is also included4 ,of still greater age but of great interest is ,john ,mawe's old work1 on diamonds and precious stones4 ,in it the author discusses in a conversational style that is very attractive much of the gem lore of his day and shows a profound knowledge of his subject1 a knowledge that was evidently first hand and practical1 ,a ,treatise on ,diamonds and ,precious ,stones1 by ,john ,mawe1 ,london4 #bnd edition4 ,printed for and sold by the author4 ,for readers of ,french1 ,jean ,baptiste ,tavernier's ,voyages1 in six volumes1 will be vastly interesting4 ,tavernier made six journeys to ,india and the ,east between #afdj and #afhj as a gem merchant during which time he purchased and brought back to ,europe many celebrated gems including the famous ,french blue diamond which he sold to ,louis ,,xiv4 and which was stolen at the robbery of the ,garde ,meuble during the ,french ,revolution4 ,tavernier describes these famous stones and many others that he was privileged to inspect in the treasuries of the ,grand ,mogul4 ,he also describes interestingly and at great length the curious manners and customs of the people of the ,east4 ,les ,six ,voyages de ,jean ,baptiste ,tavernier1 etc41 ,nouvelle edition1 ,rouen1 #agbd4 ,pliny's ,natural ,history1 to go much further back1 is full of references to gems1 and gem students should run through it 7it is to be had in ,english translation7 for such interesting bits as that in which he describes the belief that quartz crystal results from the effect of very great cold upon ice1 a belief which ,pliny himself is careful not to subscribe to4 ,he contents himself with relating what others believe in this regard4 ,both the ,hebrew scriptures and the ,new ,testament afford many references to gems with which the eager student of the subject should be familiar4 ,she is more precious than rubies 7referring to wisdom7 is but one of these4 ,in conclusion the author hopes that this little text may lead a few to pursue further this most fascinating theme and that the pursuit may bring much of pleasure as well as of profit4 ,,index ,absorption1 #ae ,adamantine luster1 #dj1 #da ,agate1 #abh1 #ach1 #agb1 #aig ,alexandrite1 #adj ,almandite 7see ,garnet7 ,altered stones1 #bdg-bdi1 #bej-beg ,amazonite1 #agf ,amethyst1 #id1 #agj1 #aie1 #aif ,aquamarine1 #adc1 #ahi ,azurite1 #acb1 #adh1 #agg1 #aii ,balances1 ,care and use of1 #bhc-bic ,beryl1 #hd1 #adc1 #aij ,bibliography1 #cja ,bloodstone1 #agb ,blue diamonds1 #ia ,blue-white diamonds1 #ia ,brazilian diamonds1 #ahb ,brilliancy1 #bjc ,brilliant cut stones1 #bcc ,brilliant1 ,theory of the1 #bje ,brittleness of gems1 #aai ,brown stones1 #ie ,bubbles in gems1 #ajc ,bubbles in glass1 #ha ,bubbles in scientific stones1 #ajc ,burmah rubies1 #aed ,cabochons1 #de1 #baf1 #bbg ,carbon1 #acf ,carborundum1 #ed1 #ee1 #ef ,carnelian1 #abh1 #ach1 #agb ,cat's-eye1 #dd-df1 #ach1 #aga ,chalcedony1 #ach ,chrysoberyl1 #de1 #he1 #abb1 #adj1 #aeg1 #ahh ,chrysoberyl cat's-eye1 #de1 #df1 #he1 #ahh ,chrysolite1 #agf ,cinnamon stone1 #add ,citrine quartz1 #afa1 #aga1 #aie1 #aif ,cleaving of diamonds1 #bjh ,cleaving of precious stones1 #bac ,color1 cause of1 in minerals1 #ae ,color of gems1 #ff-ib ,colorless stones1 #ig ,corundum gems1 #fh-gj1 #gc1 #aja1 #aba1 #acd1 #acg ,corundum gems1 defects of1 #aja ,cultured pearls1 #bgg-bgi ,cutting of diamonds1 #bji ,cutting of precious stones1 #bja-bbf ,demantoid garnet1 #fb1 #fd1 #hb1 #acj1 #add1 #afi1 #aic ,density of minerals1 #bc ,diamonds1 #fa1 #gc1 #ia1 #abj1 #acd1 #aea-aec1 #agi-ahf ,dichroism1 #ae-bb1 #aac ,dichroscope1 the1 #ag-bj ,dispersion1 #fj-fe ,double refraction1 #e ,doublets1 #da1 #bda-bdf ,emerald1 #ge-hb1 #adc1 #afd1 #ahi ,emerald1 wearing qualities of1 #aji ,epidote1 #i ,extraordinary ray1 #af ,fancy diamonds1 #ia1 #aea ,fire1 cause of1 #bjg ,forms of precious stones1 #bbg-bcf ,garnet1 #fi1 #hb1 #if1 #acj1 #adc1 #add1 #afg-agj1 #aib-aid ,garnet1 ,almandite1 #adc1 #afh1 #aic ,garnet1 ,andradite1 #hb1 #acj1 #add1 #afi1 #aic ,garnet1 ,demantoid1 #fb1 #fd1 #hb1 #acj1 #add1 #afi1 #aic ,garnet1 ,pyrope1 #add1 #afh1 #aib1 #aic ,glass1 #fb1 #adb ,glass imitations1 #ha1 #bcg-bdi ,golcondas1 #ahj ,grain base1 price of pearls per1 #bga ,hardness1 #dg-ed1 #ee-ei1 #aac ,hardness and wearing qualities1 #aai-acb ,hardness1 ,mohs's scale of1 #dh-ea ,hardness1 table of1 #ed ,hardness1 test of1 #ea-ed1 #eh ,heliodor1 #afe ,hope ,blue diamond1 #ia ,hyacinth1 #aff ,imitations of precious stones1 #bcg-bdi ,imitations of pearls1 #bgg-bhb ,imperfections1 #aaa ,imperfections in corundum gems1 #aja ,imperfections in glass1 #ha ,imperfections in scientific stones1 #ajd ,jacinth1 #aff ,jade1 #abh1 #adg1 #age1 #aig ,jadeite1 #abh1 #aig ,jargoons1 #aff ,jasper1 #abh1 #agb ,kunzite1 #aie ,lapis lazuli1 #acb1 #agg1 #aii ,labradorite1 #agf ,luster1 #ch-db ,make of diamonds1 #bje-bjg ,make of precious stones1 #bbj ,malachite1 #acb1 #adh1 #agg1 #aii ,metallic oxides1 #acg ,mineral species1 #acc-adh ,mixed cut stones1 #bcf ,mohs's scale of hardness1 #dh-ea ,moonstone1 #dd1 #de1 #aca1 #adf1 #agf1 #aih ,morganite1 #afe ,nacre1 #bhj ,naming precious stones1 #adi-afc1 #afd-agh ,nephrite1 #abi1 #aig ,occurrence of precious stones1 #agi-bjj ,olivine 7see ,demantoid ,garnet7 ,olivine1 #hc1 #agf ,onyx1 #agb ,opal1 #dd1 #aca1 #aci1 #agc ,ordinary ray1 #af ,orient of pearls1 #bfa ,oriental stones1 #hd1 #aef ,paste gems1 #adb1 #bcg-bda ,pearls1 #beh-bgf ,peeling pearls1 #bfe ,peridot1 #h1 #acj1 #agf1 #aih ,pink stones1 #ic ,pinked topaz1 #bej ,plasma1 #agb ,polishing of diamonds1 #baj ,polishing of precious stones1 #bah ,prase1 #ach1 #agb ,properties1 definition of1 #a ,purple stones1 #id ,quartz1 aventurine1 #aga ,quartz1 citrine1 #afa1 #aga1 #aie1 #aif ,quartz gems1 #de1 #abg1 #aga1 #aie1 #aig ,reflection1 total1 #bjd ,refraction1 #d ,refraction1 double1 #h-ac ,refraction1 double1 test for1 #aj1 #aab ,refractometer1 #e ,rhodolite garnet1 #afh ,roman pearls1 #bgi ,rose cut stones1 #bca ,rose quartz1 #aga1 #aig ,rubellite1 #ic ,ruby1 #ab1 #fg1 #fi1 #aec1 #aed1 #ahf ,ruby1 scientific1 #ii-ajh ,sapphires1 #fc1 #hg1 #hh1 #aee1 #ahg ,sard1 #agb ,sardonyx1 #agb ,scientific stones1 #ii-ajh ,scientific stones1 defects in1 #ajd ,scientific stones1 tests for1 #ii-ajh ,siam rubies1 #aed ,silicates1 #ada ,silk in rubies1 #aag ,slitting of precious stones1 #bac ,south ,african diamonds1 #ahd ,specific gravity1 #bc-cg1 #aad ,sphene1 #i1 #fb1 #fd ,spinels1 #ga1 #ij1 #abc1 #adj1 #aeh1 #ahh ,spodumene1 #ie1 #agj1 #aie ,star stones1 #dd1 #df1 #aeg ,step cut stones1 #bce ,structure of pearls1 #beh ,table1 of hardness1 #ed ,table of refraction1 #ab-ac ,table of specific gravity1 #bi ,tariff laws1 #bid-bii ,test for double refraction1 #aj ,testing hardness1 #ea-ed1 #eh ,testing imitations of pearls1 #bha ,testing unknown gems1 #aji-aah ,tiger's-eye1 #de1 #ach1 #aga ,topaz1 #fg1 #gc1 #ia1 #abd1 #ade1 #aei1 #ahi ,toughness in stones1 #aai ,tourmaline1 #gb1 #gg1 #gi-ha1 #if1 #adf1 #afg1 #aid ,triplets1 #gi1 #bdf ,turquoise1 #acj1 #adh1 #aih ,unit of weight1 #bhi ,variscite1 #adh ,vitreous luster1 #da ,wearing qualities of gems1 #aai ,zircon1 #i1 #fb1 #gb1 #ib1 #ig1 #abe1 #adg1 #aff1 #aia ,diamonds ,a ,study of the ,factors that ,govern their ,value ,by ,frank ,b4 ,wade ,i shall speak a little more of the diamonds1 that they who know them not may not be deceived by chapmen who go through the country selling them1 for whoever will buy the diamond1 it is needful that he know them1 444--,chap4 ,,xiv41 ,the ,voyages and ,travels of ,sir ,john ,maundeville4 ,table of ,contents ,i4--,colour4 ,,ii4--,flaws4 ,,iii4--,make4 ,,iv4--,repairing and ,recutting4 ,v4--,mounting4 ,,vi4--,buying the ,engagement ,ring4 99 99 99 99 99 ,g4 ,p4 ,putnam's ,sons ,new ,york ,london ,a ,book of ,precious ,stones ,the ,identification of ,gems and ,gem ,minerals and an ,account of ,their ,scientific1 ,commercial1 ,artistic1 and ,historical ,aspects ,by ,julius ,wodiska #hvo4 ,with #cc ,full-page ,illustrations and #d ,colored ,plates ,a description1 in altogether a new fashion1 of gems and gem minerals1 their nature and history1 comprehensible to every reader1 and of prime value to students and to jewelers4 ,the general reader will enjoy the simple descriptions of the origin1 development1 and treatment of the diamond1 sapphire1 and other precious stones1 as well as of the beautiful semi-precious stones4 ,just enough of the technical has been provided to make the new gem book a vade mecum for students of gem minerals and for the army of jewelers in the ,united ,states1 as well as their fellow-craftsmen and merchants in all ,english-speaking places4 ,the art and industry of mounting gems is somewhat elaborately covered1 especially as exemplified in the work of students at technical schools and the many unattached workers in jewelry designing and making who form a part of the ,arts and ,crafts movement4 ,some of the quaint superstitions about gems in the chapter on folklore have a curious interest4 ,the author takes cognizance of the public desire nowadays for the novel and uncommon in gems1 and shows that prospectors1 gem miners1 mineralogists1 and jewelers are co-operating to greatly lengthen the lists of popular semi-precious stones4 ,a chapter is devoted to collections of gems in museums4 99 99 99 99 99 ,g4 ,p4 ,putnam's ,sons ,new ,york ,london 99 99 99 99 99 ,transcriber's ,note3 ,inconsistent hyphenation and spellings have been standardised1 although consistent variants remain as printed4 ,minor typographical errors have been corrected without note1 whilst significant changes are listed below4 p4 #ac1 'indentity' amended to identity3 '444 of unknown identity comes along 444'2 p4 #bj1 'dischroism' amended to dichroism3 '444 but shows hardly any dichroism4'2 p4 #fg1 'quart' amended to quartz3 '444 7quartz topaz7 444'2 p4 #aah1 ',saphire d'eau' amended to ,saphir d'eau2 pp4 #adj1 #adc1 'berylium' amended to beryllium2 pp4 #adh1 #cah1 ',varicite' amended to ,variscite2 p4 #aeg1 ',csar' amended to ,czar3 '444 ,czar ,alexander ,,ii41 in whose 444'2 p4 #afg1 'rubelite' amended to rubellite3 '444 sometimes called rubellite1 and white 444'2 p4 #aij1 ',minas ,garaes' amended to ,minas ,geraes2 p4 #aii1 ',khorassan' amended to ,khorasan3 '444 province of ,khorasan in ,persia 444'2 p4 #bbg1 'caboch' amended to caboche2 p4 #beh1 'uniomargarifer' amended to ,unio margaritifera2 p4 #bih1 'mechandise' amended to merchandise3 '444 tax on imported merchandise 444'2 p4 #cja1 ',emanual' amended to ,emanuel3 '444 ,diamonds and ,precious ,stones1 by ,harry ,emanuel 444'2 p4 #cja1 ',hatten' amended to ,hotten3 '444 ,john ,camden ,hotten 444'2 p4 #cjh1 ',streetor' amended to ,streeter3 ',precious ,stones and ,gems by ,edwin ,w4 ,streeter 444'2 p4 #cad1 ',epidot' amended to ,epidote4