,,industrial ,,minerals ,,and ,,metals ,,of ,,illinois ,j4 ,e4 ,lamar ,illinois ,state ,geological ,survey ,educational ,series #h ,,state of ,,illinois ,illustration3 ,,department of ,,registration and ,,education #aife ,,illinois ,,state ,,geological ,,survey ,john ,c4 ,frye1 ,chief ,,urbana1 ,,illinois ,printed by ,authority of ,state of ,illinois1 ,ch4 #abg1 ,,irs1 ,par4 #eh4be4 7#ae,m-#d_/fe-higf7 #aj ,,industrial ,,minerals ,,and ,,metals ,,of ,,illinois ,j4 ,e4 ,lamar ,the mineral resources of ,illinois include many rocks and minerals of varied character and uses4 ,from them are made an array of everyday products whose sources may not even be recognized by the consumer4 ,the user of a glass bottle1 for instance1 rarely knows that it may have been made from ,illinois silica sand1 nor is the driver of an automobile generally aware that the ,illinois concrete highway on which he is driving probably was constructed from a mixture of cement1 sand and gravel1 or crushed stone that may have come from ,illinois pits or quarries4 ,the significance of these rocks and minerals to the economy of ,illinois is great1 although often unappreciated4 ,of the more than #fjj million dollar value of all ,illinois mineral production in #aifc1 almost #bjj million was from industrial minerals4 ,the diversity and widespread distribution of these mineral resources lend variety and balance to the mineral industry of the state1 and their production1 processing1 and utilization afford direct and indirect employment to many people4 ,the term industrial minerals is used as a convenient group term for nonmetallic minerals that are not fuels4 ,in ,illinois they include limestone1 dolomite1 clay1 shale1 silica sand and other sands1 fluorspar1 tripoli 7amorphous silica71 ganister1 novaculite1 sandstone1 feldspar-bearing sands1 barite1 gypsum1 anhydrite1 brines1 greensand1 oil shale1 marl1 peat1 humus1 and tufa4 ,the metallic minerals of ,illinois are galena 7lead ore71 sphalerite 7zinc ore71 pyrite1 and marcasite4 ,this booklet briefly and nontechnically discusses the foregoing materials and some of the work the ,illinois ,state ,geological ,survey does in gathering information about their occurrence1 and character and in developing new uses4 ,the assistance of many ,survey staff members and of many people in the ,illinois mineral industry in the preparation of this booklet is acknowledged4 ,,limestone ,limestone is a most versatile rock4 ,without it there would be no portland cement for making concrete roads and buildings1 no lime for plastering and chemical use1 no agricultural limestone for farms1 and no crushed limestone for driveways4 ,a wide variety of industries1 from steel making to glass manufacturing1 use limestone in one way or another4 ,the early settlers of ,illinois recognized the value of limestone and quarried stone blocks and slabs for making foundations1 chimneys1 and even houses4 ,for mortar they used a mixture of sand and lime to hold the blocks together4 ,the lime was made by heating limestone red hot in simple furnaces or kilns1 the ruins of a few of which may still be seen4 ,kinds of ,limestone ,illinois has two principal varieties of limestone1 referred to technically as limestone and dolomite4 8,limestone0 may be used as a general name for both varieties4 ,limestone consists principally of crystalline particles of the mineral calcite 7fig4 #a74 ,this mineral is glassy in appearance and is composed of calcium1 carbon1 and oxygen combined to form calcium carbonate--,ca,c,o4 ,dolomite is largely made of crystalline particles of the mineral dolomite1 which also has a glassy appearance and consists of calcium1 magnesium1 carbon1 and oxygen--,ca,mg7,,co74 ,the crystalline particles of limestone and dolomite vary in size4 ,some are coarse enough to be seen easily1 others are so small that they can be distinguished only with a microscope4 ,formation of ,limestone and ,dolomite ,almost all ,illinois limestones were formed in seas that covered ,illinois millions of years ago4 ,the many different limestone formations in ,illinois suggest that oceans covered all or part of the area several times4 ,numerous kinds of shell fish1 corals1 and other marine animals lived in these oceans and had shells and other hard parts made of calcium carbonate4 ,through countless generations1 these animal remains accumulated on the ocean floor and gradually were compacted and cemented into limestone 7fig4 #b74 ,other ,illinois limestones1 however1 were formed by the hardening of muds composed mainly of calcium carbonate that accumulated on the floors of the ancient seas4 ,still other limestones were formed of a combination of animal remains and lime mud4 ,illustration3 ,figure #a--;,calcite crystals4 ,limestone is made up mainly of calcite crystals1 but they are less perfectly formed and are crowded together4 ,the coral reefs of the ,south ,pacific ,ocean have their counterparts in ,illinois4 ,the ancient ,illinois oceans contained extensive reefs that were built up just as the modern reefs have been4 ,in northern ,illinois1 around ,chicago for instance1 a number of the ancient reefs are now the site of stone quarries4 ,in southwestern ,illinois such reefs are a source of petroleum4 ,the dolomites of ,illinois probably were originally limestones1 but1 either while the limestones were still beneath the sea or after the sea had withdrawn1 magnesium was exchanged for some of the calcium in the limestones4 ,if the exchange took place under the sea1 the sea water was the source of the magnesium4 ,if it happened when the limestones were a part of the land1 the magnesium was brought in by water circulating through the rock4 ,many of the marine animal fossils became difficult to recognize after the change1 and the texture and general appearance of the rock also were altered4 ,some of it became noticeably porous4 ,illustration3 ,figure #b--,limestone containing fossils4 ,an ,archimedes screw appears at lower left1 lace-like bryozoa in the center1 and fluted brachiopod shells at top and center4 ,uses of ,limestone and ,dolomite ,some of the major uses for ,illinois limestone and dolomite are mentioned below4 ,not every limestone or dolomite can be used for all purposes because for each use the stone must fulfill special requirements of a chemical or physical nature4 ,for example1 it must have high purity for lime1 resistance to wear and weather for roads and buildings1 and a pleasing appearance for decorative stone and marble4 ,lime4--,when limestone or dolomite is heated to a high temperature1 it undergoes a change and carbon dioxide is liberated4 ,the weight of the gas set free is equal to somewhat less than half the weight of the rock if the rock is pure4 ,the solid product remaining after the gas has been driven off is known as lime4 ,the heating process is called burning4 ,besides being used in making mortar and plaster1 lime is valuable in many other ways1 especially in various chemical processes of modern industry4 ,plants at ,chicago and ,quincy make lime from ,illinois limestone and dolomite4 ,illustration3 ,figure #c--;,an ,illinois dolomite quarry4 ,cement4--,portland cement1 sometimes called simply cement1 is made at ,la,salle1 ,oglesby1 and ,dixon in northern ,illinois from limestone and a smaller1 carefully measured amount of clay or shale4 ,cement also is made at ,joppa in southern ,illinois4 ,the blend of materials is thoroughly ground and mixed1 then heated at a high temperature in huge rotating horizontal furnaces1 called kilns1 until it forms a clinker4 ,after it cools1 the clinker is ground to a flourlike powder4 ,this is basically the cement that binds together the mixture of sand and limestone 7or dolomite71 or of sand and gravel1 to make the concrete from which roads1 bridges1 buildings1 and other structures are made4 ,aggregate4--,the crushed stone used in making concrete is known as concrete aggregate4 ,this is a major use for ,illinois limestones and dolomites4 ,large amounts of stone aggregate also are used in bituminous roads1 popularly called 8blacktop0 roads4 ,agricultural ,uses4--,agricultural limestone 7agstone7 is applied to farm land to neutralize soil acids and otherwise benefit the soil4 ,both limestone and dolomite are so used4 ,chickens are fed small limestone chips to provide calcium for the formation of egg shells4 ,pigs and cows get calcium from mineral supplements containing powdered pure limestone4 ,illustration3 ,figure #d--;,an underground limestone mine4 ,other ,uses4--,illinois limestone or dolomite is used in steel making1 as building stone and marble1 as road stone1 as ballast for the road beds of railroad tracks1 for making refractory dolomite used in the steel industry1 and for a variety of less common uses4 ,quarries ,there are about #bjj stone quarries in ,illinois4 ,most of the larger quarries 7fig4 #c7 are in the ,chicago1 ,joliet1 ,kankakee1 and ,east ,st4 ,louis areas1 but one or more limestone or dolomite quarry occurs in many counties4 ,if all the stone taken from ,illinois quarries in #aifc were removed from a hole #ajj feet square1 the hole would penetrate into the earth about #h miles4 ,it would take more than #cej1jjj railroad cars holding #ajj tons each to haul away the stone4 ,limestone1 dolomite1 and their products added over #hj million dollars to the economy of the state in #aifc1 approximately #h dollars for each person in ,illinois4 ,most ,illinois limestone and dolomite is quarried from open pits1 but in some places1 as in the rocky bluffs along the ,mississippi ,river1 the stone is taken from underground mines 7fig4 #d74 ,there is also a dolomite mine in ,chicago4 ,at the quarries the first step is the removal of the earth overlying the stone4 ,next1 in both pit and mine1 the stone is blasted to free it from the parent deposit and break it into pieces4 ,mechanical shovels 7fig4 #c7 load the stone into trucks that take it to the crushing plant where powerful crushers further break the stone into pieces4 ,the pieces are sorted into various sizes by large screens4 ,at some of the plants1 the stone is ground into powder4 ,location of ,limestone ,deposits ,the geologic map of ,illinois prepared by the ,illinois ,state ,geological survey shows1 with reasonable exactness1 what bedrock formations would crop out at the surface if the overlying clay1 sand1 gravel1 and earth were removed4 ,thick dolomite formations would be exposed in much of the northern fifth of the state1 but would be rare elsewhere4 ,thick limestone formations would occur in an almost continuous zone1 varying in width from #c to #be miles1 along the ,mississippi ,river from ,rock ,island to southern ,illinois and then eastward across the extreme southern tip of the state4 ,limestone also would be seen along the ,illinois ,river from ,havana southward4 ,in the central area of the state1 limestones are present1 but they are rarely over #be and often less than #ae feet thick4 ,consequently1 most of the larger quarries are in the northern1 western1 and southern parts of ,illinois4 ,the thinner limestones1 nonetheless1 are of much importance and are quarried at many places1 chiefly to provide agricultural limestone1 road stone1 and limestone for making cement4 ,the ,geological ,survey locates and maps limestone and dolomite deposits and analyzes and tests samples to determine the best possible uses for the stone4 ,many reports have been published about the character and general use of the deposits in various parts of the state4 ,other reports deal with the use of limestone and dolomite for specific purposes such as cement making1 building and decorative stone1 rock wool1 terrazzo chips1 and lime4 ,,metallic ,,ores ,,and ,,fluorspar ,lead and ,zinc ,lead mining was one of the earliest industries of ,illinois4 ,the early settlers' need for bullets for procuring food and for defense of their lives and property made lead an important commodity1 and the deposits of lead ore in the northwestern corner of ,illinois were quickly exploited4 ,the ore was the mineral galena 7fig4 #e71 for which the city of ,galena in ,jo ,daviess ,county is believed to have been named4 ,illustration3 ,figure #e--;,galena with cubic cleavage blocks in foreground4 ,galena is a dark1 shiny mineral that breaks readily into cubes or combinations of cubes4 ,it is composed of lead and sulfur 7,pb,s74 ,galena itself is not suitable for use as a metal2 the lead must first be separated from the sulfur4 ,the earliest method of recovering lead from galena was crude4 ,a pile of logs1 smaller pieces of wood1 and ore was built on sloping ground4 ,just below it a pit was dug4 ,when the wood was set on fire1 the heat caused the lead and sulfur to separate1 and the molten lead trickled down into the pit4 ,the smelting process was later improved1 and stone 8furnaces0 were built to house the operations4 ,crevice ,deposits and ,residual ,deposits4--,most of the lead ore mined in the early days of the northwestern ,illinois mining district came from crevice deposits in the dolomite bedrock and from residual deposits at or near the surface of the ground4 ,the crevices were vertical narrow joints or fissures4 ,ore was not continuously present along them but occurred from place to place in 8pods0 7fig4 #f and fig4 #g74 ,dimensions of the pods varied1 but typical ones were about #c feet wide1 #e feet high1 and a few to a few hundred feet long4 ,the galena1 for the most part1 occurred in a mixture of clay and weathered dolomite that filled1 or partly filled1 the crevices4 ,the residual deposits were found where the action of the weather for many thousands of years had dissolved the dolomite from the outcropping parts of a crevice deposit and left behind a residue of brown or red clay containing galena4 ,some of the crevice and residual deposits worked by the early miners cropped out at the surface1 but most of them were covered by earth4 ,other crevices were exposed in the bluffs of the ,mississippi ,river and extended back into them for #a1jjj feet or more4 ,illustration3 ,figure #f--;,diagrammatic cross section of two crevice deposits4 ,a reaches ground surface and is filled with clay2 ,b is only partly clay filled4 ,galena coats parts of the walls and occurs as pieces scattered through the clay4 ,typical crevices are about #c feet wide and #e feet high4 ,,soil ,a ,,galena ,,clay ,,and ,,rotted ,,dolomite ,b ,,galena ,,clay ,,and ,,rotted ,,dolomite ,,dolomite ,when the richer deposits of ore in the crevices were worked out1 some mines were deepened into the dolomite bedrock1 but usually less rather than more galena was found4 ,as the amount of galena decreased1 however1 another mineral1 which had been present before in only small amounts1 was found in increasing quantities4 ,this was sphalerite--a yellow1 brown1 or black mineral of resinous appearance that is composed of zinc and sulfur 7,zn,s74 ,it does not look like a metallic ore4 ,at first the sphalerite was not used because there were no smelters in the area that could separate the zinc from the sulfur with which it was combined in the ore4 ,between #ahej and #ahgj1 however1 smelters were built in northwestern ,illinois and southern ,wisconsin and the ore was shipped there4 ,sphalerite is now the principal ore mineral produced in northwestern ,illinois4 ,the sphalerite and galena of southern ,illinois1 described later1 are similar to that found in northwestern ,illinois4 ,illustration3 ,figure #g--;,crevice lead mine4 ,miner pries ore loose and pushes it into car at bottom of crevice4 ,shiny galena layer occurs above his head and another at level of his waist4 ,mining and ,milling4--,one large mine is producing zinc and lead near ,galena at present4 ,smaller mines operate irregularly4 ,the ore may occur as pockets1 irregularly shaped rather flat masses1 vertical or inclined veins 7fig4 #h71 or small particles scattered through the dolomite4 ,the principal ore bodies that have been worked in recent years have been of irregular shape1 both horizontally and vertically1 and usually have been between #ej and #bjj feet wide and from a few to as much as #ajj feet high4 ,they lie at a depth of roughly #cjj feet4 ,blasting is required to loosen and break the ore4 ,at the large mine the ore is brought to the surface by a hoist4 ,in some relatively shallow mines an inclined tunnel has been driven to the ore body and the ore brought to the surface in trucks4 ,illustration3 ,figure #h--;,diagrammatic cross section of a zinc ore deposit showing flats and pitches4 ,the deposit occurs in limestone and dolomite4 ,much of the ore is a mixture of dolomite1 limestone1 calcite1 and sphalerite4 ,typical dimensions of such a deposit are about #cj feet high and #ajj to #bjj feet wide4 ,,ore ,,pitches ,,flats ,because the ore consists of galena and sphalerite attached to and scattered through dolomite1 it must be milled to free and separate the metals from the rock4 ,crushing1 grinding1 and other operations are involved4 ,the dolomite is discarded and the galena and sphalerite concentrates are shipped away to be smelted4 ,no smelters have operated in the ,galena area for some time4 ,aids to ,prospecting4--,finding deposits of ore #cjj feet underground is not easy4 ,inspection of the surface usually tells little4 ,to find and outline a commercial ore deposit many holes often must be drilled to explore the unexposed rock strata4 ,because this is a costly process1 every possible means is employed to drill the holes where ore is most likely to be found4 ,this is where geologists are useful--geologists of the mining companies and of the ,illinois ,geological ,survey4 ,three examples of how their investigations help to find ore are given here4 ,it was noted early in the development of the northwestern ,illinois mining district that zinc ore deposits were most common along small downfolds in the bedrock1 called synclines1 that were a few hundred feet wide and a mile or so long4 ,the synclines were associated with much larger synclines that extended for several miles4 ,a map prepared by the ,illinois ,geological ,survey shows the possible location and extent of many of these downfolds and has had much practical use in the selection of the most promising areas for test drilling to find ore4 ,the ,survey also collects the records of borings made by companies and individuals in their search for ore4 ,the records are on permanent file at the ,survey offices and are valuable in several ways4 ,some indicate where no ore was found and where it is1 therefore1 useless to drill further2 others show only traces of ore but suggest that more drilling in the vicinity might discover a deposit large enough to be mined profitably4 ,still other records are of borings that encountered rich ore in which mines have been developed4 ,the third aid to prospecting is the study of ore bodies and their minerals to determine how the deposits were formed4 ,the ore bodies have been and are being studied in the mines4 ,ore specimens are carefully examined in the ,survey laboratories4 ,if geologists can learn how the known deposits were formed1 it may be possible to direct exploration into promising new areas4 ,fluorspar ,in the southeastern tip of ,illinois lie deposits of a mineral that contains the chemical element fluorine4 ,this element is used in making the propellant that activates aerosol sprays1 a plastic that resists chemicals and oil and is strong enough to be used for bearings1 compounds that are said to help to prevent tooth decay1 and many other useful chemicals4 ,the mineral is fluorite 7fig4 #i71 commonly called fluorspar4 ,it is composed of calcium fluoride 7,ca,f71 a compound of calcium and fluorine1 and is a glassy mineral that is generally white or gray but may be purple1 rose1 yellow1 blue1 or green4 ,in rare instances it is colorless4 ,fluorspar mining in ,hardin and ,pope ,counties began with lead mining4 ,galena was first discovered there in #ahci in a well being dug at the town of ,rosiclare4 ,mining of galena began in the early #ahdj's1 and somewhat later ore was being smelted by three furnaces1 all of which have long since disappeared4 ,the veins that were worked for galena also contained fluorspar1 but as there was little or no use for fluorspar in the #ahdj's it was considered waste4 ,in time1 uses developed1 however1 and about #ahgj it was mined and shipped in commercial quantities4 ,since then the tonnage and value of the fluorspar produced from the ,rosiclare area have increased until fluorspar is the major product4 ,illustration3 ,figure #i--;,group of cubic fluorite crystals4 ,the fluorspar mining district north of the town of ,cave in ,rock in eastern ,hardin ,county also was an early producer of galena4 ,in that area the fluorspar-galena deposits are elongate and approximately flat4 ,the first miners followed the ore bodies from outcrops by tunneling into the hillsides4 ,in the late #aicj's and early #aidj's1 many holes were drilled into the bedrock in search of new deposits4 ,ore was found that contained not only galena and fluorspar but also important amounts of sphalerite4 ,vein ,deposits4--,in the ,rosiclare district1 the fluorspar and its accompanying minerals occur as steeply inclined veins a few inches to #be feet or more wide 7fig4 #aj71 usually in limestone strata4 ,the veins are not uniformly thick but widen or narrow from place to place both vertically and horizontally4 ,they occur along faults--planes along which the rocks of the earth's crust have broken and slipped4 ,a fault may be a single plane of slippage but more often is a zone of broken and displaced rocks4 ,in most of the faults that contain fluorspar1 the slippage is vertical1 or nearly so4 ,along one of the faults in the ,rosiclare district1 the rocks on one side of the fault have moved downward as much as #fej feet in relation to the rocks on the other side4 ,some faults are more than #aj miles long1 and the depth to which they extend into the earth is unknown4 ,fluorspar has been mined from one of them at depths of #hjj feet4 ,not all faults1 nor all parts of any one fault1 contain fluorspar4 ,illustration3 ,figure #aj--;,diagrammatic cross section of fluorspar vein along a fault4 ,the strata on the left side of the fault have moved downward with reference to those on the right side4 ,,soil ,,fault ,,fluorspar ,,vein ,,along ,,fault down ,,sandstone ,a ,,limestone ,b ,,shale ,c ,,sandstone ,d ,,limestone ,e up ,,limestone ,b ,,shale ,c ,,sandstone ,d ,,limestone ,e ,bedding ,deposits4--,in contrast to the vein deposits of the ,rosiclare district1 the bedding deposits of the ,cave in ,rock area are flat1 or nearly flat1 commonly #e to #ae feet thick1 and from a few to #bjj feet wide 7fig4 #aa74 ,they may be as much as #bjjj feet long1 widening or narrowing and thickening or thinning throughout their extent4 ,they are called bedding deposits because they lie along the beds or layers of the limestone in which they occur4 ,most of the ore bodies are associated with a fracture or a small fault4 ,illustration3 ,figure #aa--;,diagrammatic cross section of bedding deposit of fluorspar1 lead1 and zinc ore4 ,,soil ,,sandstone ,,and ,,shale ,,ore ,,limestone ,,fracture ,,or ,,small ,,fault ,grades and ,uses of ,fluorspar4--,there are three principal grades of fluorspar--metallurgical1 acid1 and ceramic4 ,the metallurgical spar is used as a flux in making steel and in metal foundries4 ,acid spar is used to make hydrofluoric acid1 which plays a part in the preparation of uranium isotopes and in the production of a synthetic mineral essential in refining aluminum4 ,the acid is also used in the production of high-octane gasoline and is the basis for a variety of important chemical compounds1 among them refrigerants and insecticides4 ,ceramic grade fluorspar is used in making enamels1 glazes1 and certain kinds of glass4 ,mining and ,milling4--,fluorspar and its associated ores are mined in different ways in the ,rosiclare and ,cave in ,rock districts because the types of deposits differ4 ,however1 in both areas most of the larger mines are entered by vertical shafts4 ,in the mines1 explosives are placed in holes drilled by machines and are then detonated to shoot down the ore 7fig4 #ab74 ,mine cars1 trucks1 or conveyor belts carry the ore to the bottom of the mine shaft where hoists raise it to the mills at the surface4 ,in the mills a variety of ore-classifying machines separate the galena1 sphalerite1 and fluorspar from the waste mineral materials 7chiefly limestone and calcite7 with which they occur4 ,some fluorspar after the separation process is almost flour-fine4 ,to increase its use1 much of this spar is mixed with a binder and made into pellets or briquets one-half to one inch in size4 ,illustration3 ,figure #ab--,machine loading fluorspar ore in mine near ,cave in ,rock4 ,geological and ,chemical ,studies4--,because much of the fluorspar produced in southern ,illinois has come from veins along faults1 geologists have mapped the faults of the area by investigating the distribution and nature of the various bedrock outcrops4 ,the work was complicated by the mantle of earth and vegetation that covers the bedrock at many places4 ,however1 a geologic map was made that shows where the various rock formations--sandstone1 limestone1 and shale--lie beneath the surface and where the numerous faults crisscross the district4 ,the first geologic map of the fluorspar district was made in #aibj by the ,illinois and ,u4 ,s4 ,geological ,surveys4 ,new maps on a much larger scale have been made recently by the ,illinois ,survey to meet the needs of the modern fluorspar industry4 ,the ,illinois ,survey also has studied the ores and ore deposits of southern ,illinois to determine how they were formed4 ,the records of many borings and pits sunk to find ore have been collected and filed at the ,survey to guide future prospecting4 ,survey chemists are finding new uses for ,illinois fluorspar4 ,their research has produced new organic fluorine compounds that are being tested for use in agriculture1 medicine1 and industry4 ,they also have worked out easier and cheaper methods of making certain fluorine compounds4 ,survey chemical engineers have helped to obtain needed information about the physical properties of the pellets made from fluorspar powder4 ,origin of ,illinois ,ore ,deposits ,the ore deposits of northwestern and southern ,illinois were formed so many millions of years ago that it is possible to propose only theories of their origin4 ,most geologists think that the minerals1 dissolved in warm or hot water1 came from deep in the earth4 ,perhaps the mineral-bearing water came from1 or was associated with1 rocks that were or had been molten 7igneous rocks71 but it may have had some other source4 ,why the ores occur where we now find them is not fully known4 ,the cooling of the solutions and the lessening of pressure as the solutions rose toward the surface may have had a part in ore deposition4 ,faults and the nature of the rocks encountered by the depositing solutions also appear to have had an influence4 ,illinois as a ,mining ,state ,although ,illinois is not usually thought of as a mining state1 northwestern and southern ,illinois together produced in #aifc nearly #e1jjj1jjj worth of zinc1 about #fjj1jjj worth of lead1 and #f1ejj1jjj worth of fluorspar4 ,the annual total value is about #ab1jjj1jjj4 ,the southern ,illinois fluorspar district has another distinction--for many years its mines have been the major domestic source of the nation's fluorspar4 ,,silica ,,sand ,about #dej1jjj1jjj years ago1 a shallow ocean covered ,illinois4 ,its waves and currents carried clean white sand and deposited it as curving beaches1 sand bars1 and dunes4 ,this sand differed from many sands in that it was composed almost exclusively of grains of the mineral quartz instead of being a mixture of quartz and other minerals4 ,quartz is composed of silica 7,si,o71 and sands such as the ancient ,illinois sand that are composed of quartz are known as silica sands4 ,quartz is very hard and will scratch glass and some steel4 ,perfect quartz crystals1 which are rare1 are longer than they are thick and end in pyramids4 ,probably not many grains of the ancient sand came from perfect crystals2 they more likely resulted from the decaying and breaking down of rocks such as granite1 which are mixtures of quartz grains and other mineral particles4 ,the quartz grains probably did not come directly from their source to ,illinois4 ,instead1 it is likely they first were deposited elsewhere and formed into sandstone4 ,that sandstone was subsequently broken down by weathering agents and the grains transported to the ancient ,illinois sea by streams4 ,as a result of the erosive action of the agents that transported them1 many of the originally angular grains1 particularly the coarser ones1 were rounded and their surfaces dulled like that of frosted glass 7fig4 #ac74 ,consequently1 they appear white1 although they actually are colorless4 ,since the ancient sea deposited its silica sand1 other seas have covered ,illinois at various times and each has left deposits of sand1 mud1 or limy materials4 ,the silica sand thus was buried by hundreds of feet of other sediments and became sandstone4 ,this sandstone is called the ,st4 ,peter ,sandstone4 ,it is named from the ,st4 ,peter ,river1 now the ,minnesota ,river1 in ,minnesota where the sandstone was first described and named by geologists4 ,the overlying deposits also were consolidated into rock4 ,st4 ,peter ,sandstone is exposed at the surface at many places in northern ,illinois and in one small area in the western part of the state4 ,the sandstone exposed in northern ,illinois generally varies from #abe to #cjj feet thick4 ,the fact that it crops out at the surface indicates that the materials that formerly covered it have been removed4 ,the uncovering was not a single1 simple event but rather a series of events that took place at various times during the many years since the ,st4 ,peter sand was deposited4 ,among these was the up-bowing of the rocks of central northern ,illinois into a broad arch4 ,streams then began to cut across the arched rock1 slowly but persistently stripping away the top layers until the core of the arch was laid bare4 ,among the rocks thus exposed was the ,st4 ,peter ,sandstone1 which may be seen in northern ,illinois in the valleys and tributaries of the ,rock ,river near ,dixon and ,oregon and along the ,illinois and ,fox ,rivers and some of their tributaries near ,ottawa1 ,wedron1 ,millington1 and ,troy ,grove4 ,the ,st4 ,peter ,sandstone at ,starved ,rock and ,matthiessen state parks near ,la,salle and along the highway between ,dixon and ,oregon is eroded into scenic bluffs and canyons4 ,illustration3 ,figure #ac--;,enlarged photograph of ,st4 ,peter sand showing the rounded and frosted character of the grains4 ,silica ,sand ,industry ,the ,illinois silica sand industry is based on the ,st4 ,peter ,sandstone4 ,it centers around ,ottawa1 ,wedron1 ,troy ,grove1 and ,utica in ,la,salle ,county and in ,oregon in ,ogle ,county4 ,two principal grades of silica sand are produced--washed and crude4 ,the value of the silica sand produced in ,illinois in #aifc was about #i1jjj1jjj4 ,washed ,sand4--,although the ,st4 ,peter ,sandstone is composed almost entirely of quartz grains1 a small amount of clay is present4 ,for some uses it is not necessary to remove the clay1 for others its elimination is important and is achieved by washing the sand4 ,in the mining of silica sand that is to be washed1 the sandstone is first blasted loose from the parent deposit to break it into sand or pieces of various sizes4 ,some of the larger pieces may require a second blasting to disintegrate them4 ,at some pits the material is loaded mechanically and transported to the washing plant4 ,at others a powerful stream of water is directed against the broken sandstone 7fig4 #ad7 and the resulting mixture of sand and water flows to a collecting basin from which it is pumped through large pipes to the processing mill4 ,in both types of operation the sand is thoroughly washed at the plants4 ,after it is washed1 the sand is further processed to suit the needs of its users4 ,much of it is screened into different size grades4 ,uses of ,washed ,silica ,sand4--,the washed silica sand produced in ,illinois has many uses1 some of which are briefly mentioned below4 ,the suitability of the sand for some purposes depends in part on its having been screened to specified sizes4 ,the high purity of ,illinois washed silica sand makes it suitable for making glass1 which is more than half silica sand4 ,each year over a million tons is used for this purpose4 ,the purity of the sand also is of importance for chemical and metallurgical uses such as the manufacture of sodium silicate and silicon carbide and in alloying4 ,the hardness of the sand makes it useful for grinding large sheets of plate glass to prepare them for polishing and also makes it an effective abrasive agent for sandblasting4 ,metal castings in foundries and the exteriors of buildings are cleaned by this process4 ,illinois produces thousands of tons of sand yearly for such abrasive purposes4 ,because the coarser grains of the washed silica sand are rounded1 strong1 and available in uniform sizes1 oil operators use thousands of tons of it annually in the hydraulic fracturing of oil-bearing strata4 ,the sand is mixed with oil1 other petroleum products1 or water and is forced by powerful pumps into sandstone or limestone formations that contain oil4 ,the great force thus exerted opens fractures in the rock strata and pushes the liquid and sand into them4 ,when the pressure is relieved1 the sand grains serve as props to hold the fractures open4 ,the oil can then flow more easily into the wells and oil production is thus increased4 ,the washed sand1 because it is clean and does not dissolve in water1 is used to filter impurities from drinking water4 ,its whiteness makes it a desirable constituent in plaster1 mortar1 and precast building panels4 ,illustration3 ,figure #ad--;,hydraulic mining of silica sand near ,ottawa4 ,because it is round grained and withstands high temperatures without melting1 large tonnages of the washed silica sand are used to make molds into which molten metal is poured to make various kinds of castings4 ,a special type of coarse silica sand from ,illinois that is carefully prepared so that it is always of the same grain size is used throughout the world as a standard in laboratories that test cement and other commercial products4 ,illustration3 ,figure #ae--,loading crude silica sand4 ,some silica sand is ground to a fine1 white powder4 ,the powder1 called ground quartz1 ground silica1 silica flour1 or potter's flint1 has many uses4 ,it is an ingredient in paints1 potters use it in making pottery and china1 it goes into scouring powders1 into molds used for precision types of metal castings1 and into enamels4 ,crude ,silica ,sand4--,the crude silica sand produced from the ,st4 ,peter ,sandstone generally is yellow or yellowish white and is not washed before it is used4 ,it probably originally was white1 but iron oxide1 similar to the rust that forms on iron1 now coats many of the sand grains and colors the small amount of clay in the sand4 ,thousands of tons of crude silica sand are mined annually 7fig4 #ae74 ,because it is highly heat resistant1 foundries buy much of it to make the molds used for castings1 especially steel castings1 and for automobile engine blocks1 train wheels1 and a variety of other metal products4 ,crude silica sand also is used around industrial furnaces to seal cracks and openings to prevent the loss of heat1 in certain ceramic products1 and for adjusting the silica content of the raw materials used for making portland cement4 ,studies of the ,st4 ,peter ,sandstone ,the ,illinois ,geological ,survey has made field studies and prepared maps showing where the ,st4 ,peter ,sandstone is exposed in northern and western ,illinois4 ,many samples have been screened and examined under a microscope to determine how the sand of different deposits1 or different parts of the same deposit1 varies in grain size and mineral composition4 ,the possibility of using ,illinois silica sand for making silica brick also has been investigated4 ,,gravel ,,and ,,sand ,some #bbe1jjj years ago1 most of what is now ,illinois was buried under the ice of the ,illinoian glacier4 ,two earlier glaciers had covered large parts of ,illinois1 and another1 known as the ,wisconsinan glacier1 came into the state later1 about #ej1jjj to #gj1jjj years ago 7fig4 #af74 ,the relatively small glaciers in the ,united ,states today1 such as those in the northern ,rocky ,mountains1 are concentrated in valleys and are called valley glaciers4 ,the glaciers that covered ,illinois were parts of huge ice sheets that extended over much of the ,north ,american continent and are called continental glaciers4 ,they spread over most of ,canada1 then pushed southward to bury ,new ,england and a great area in the north-central part of the ,united ,states north of the ,ohio and ,missouri ,rivers4 ,formation of ,gravel and ,sand ,deposits ,as the glacial ice edged slowly southward from ,canada1 it froze fast to and picked up soil and loose pieces of rock1 with enormous force tore away huge chunks of bedrock1 and mixed and ground these materials together 7fig4 #ag74 ,into ,illinois the glacier carried rock materials from ,canada1 ,wisconsin1 ,minnesota1 and ,michigan2 other rock fragments were picked up in ,illinois as the ice front advanced4 ,when the glacier melted1 it left behind its load of rock flour and rock fragments1 much of it as a gray clay containing pebbles1 cobbles1 and boulders4 ,geologists call such deposits glacial till4 ,illustration3 ,figure #af--;,extent of the exposed deposits of the ,wisconsinan1 ,illinoian1 and ,kansan glaciers in ,illinois1 and the unglaciated areas of the state4 ,,unglaciated ,,wisconsinan ,,glacier ,freeport ,fulton ,peoria ,decatur ,charleston ,,illinoian ,,glacier ,kewanee ,waterloo ,carbondale ,harrisburg ,,kansan ,,glacier ,,unglaciated ,hardin ,the ice in the continental glaciers usually crept forward1 sometimes slowly1 sometimes more rapidly4 ,whether the front of a glacier moved forward or back depended on the balance between the rate of forward motion of the ice and the rate of melting4 ,when the ice advanced faster than it melted1 the front of the glacier moved forward4 ,when the glacial ice melted faster than it moved forward1 the front of the glacier receded4 ,when the rates of melting and advance were about equal1 the front of the glacier stood still or moved back and forth in a narrow zone4 ,illustration3 ,figure #ag--,striated boulder4 ,scratches and flattened surfaces were caused by abrasion by other rocks while boulder was embedded in glacial ice4 ,when such a more or less stationary front existed1 an enormous amount of clay1 silt1 sand1 pebbles1 and boulders was deposited in a belt only a few miles wide along the front of the glacier1 creating a line of hills and ridges that extended for many miles4 ,such belts1 called end moraines1 can be seen today in many parts of ,illinois4 ,the building of end moraines often was accompanied by the release of great quantities of water 7meltwater7 from the melting ice4 ,the water1 laden with rock debris1 flowed from the front of the glacier in many streams4 ,as the meltwater flowed away from the glacier it sorted its load1 although the sorting was rarely perfect4 ,the heavy boulders and pebbles usually were dropped first1 then the sand1 next the silt1 and finally the clay4 ,in general1 the farther the deposits were from the glacier the finer they were4 ,the major streams frequently carried pebbles #ej to #ajj miles from the glacier and it was many more miles before all the sand was dropped4 ,they carried some of the fine silt and clay as far as the ,gulf of ,mexico4 ,sometimes the floods of glacial water were greater and flowed faster than usual and so were able to carry coarse rock materials farther4 ,as a result1 gravel was laid down on top of earlier sand deposits4 ,later there may have been further sand deposition4 ,the debris-laden meltwater that flowed into valleys often deposited in them a considerable filling of sand and gravel4 ,some valleys were filled to a depth of as much as #ajj feet4 ,such deposits are called valley fills or valley trains4 ,modern streams have cut their courses into many of these fills and even worn away large parts of them4 ,remnants of valley train deposits are now large terraces or benches along streams1 many of them well above the present stream channels4 ,where many small streams flowed from the glacier1 they deposited sand and gravel as a large apron in front of the glacier4 ,such deposits are called outwash plains and many of them extend for miles4 ,two other types of sand and gravel deposits made by glacial meltwaters also are significant4 ,one was formed where water issued from the front of a glacier or poured into holes or crevasses in the ice4 ,the sand and gravel in the water formed a deposit that now appears as a rounded hill associated with a terminal moraine and is called a kame4 ,the second type of deposit was laid down in beds of streams flowing under1 through1 or on the glaciers and was left as a more or less continuous ridge of sand and gravel when the ice melted4 ,such a deposit is called an esker4 ,some eskers in ,illinois are about a quarter of a mile wide and several miles long4 ,typical are the ,kaneville ,esker northwest of ,aurora1 the ,adeline ,esker south of ,freeport1 and the ,exeter ,esker west of ,jacksonville4 ,the deposits of both the ,illinoian and ,wisconsinan glaciers are widely distributed throughout the state4 ,melting of the ,illinoian glacier caused comparatively little flooding2 consequently1 extensive gravel deposits were formed in only a few places4 ,the ice of the ,wisconsinan glacier1 however1 melted rapidly and produced great floods laden with sand and gravel4 ,thus1 most major gravel deposits in ,illinois are related to the ,wisconsinan glacier4 ,wind sweeping across the sand and gravel deposits blew the sand into hills or sand dunes near such places as ,havana1 ,prophetstown1 ,kankakee1 and ,watseka4 ,even today the wind shifts sand of long-forgotten glacial floods4 ,studies of ,glacial ,deposits ,the foregoing discussion of glaciers and their deposits is greatly simplified4 ,for some time geologists of the ,illinois ,geological ,survey have been mapping the moraines1 valley trains1 outwash plains1 and other glacial deposits of the state4 ,because the ,illinoian and ,wisconsinan glaciers advanced and retreated several times1 they built many moraines4 ,the ,survey has made a map 7fig4 #ah7 that shows the complexity of the moraines left by the ,wisconsinan glacier4 ,they are roughly concentric1 indicating that the general shape of the glacier front remained about the same4 ,principal ,commercial ,sources of ,sand and ,gravel ,the sand and gravel industry is widely distributed throughout ,illinois4 ,the principal commercial sources of sand and gravel are valley trains and outwash plains4 ,the ,fox1 ,rock1 ,illinois1 ,mississippi1 and ,wabash ,rivers and many smaller streams have terraces in their valleys that are parts of valley trains4 ,in these deposits are some of the largest sand- and gravel-producing operations in the state4 ,composition ,an examination of glacial gravel deposits in ,illinois reveals pebbles and larger pieces of many kinds of rock4 ,some are gray1 others white1 pink1 brown1 or black4 ,they commonly include limestone1 dolomite1 granite1 and many rocks with less common names such as quartzite1 schist1 and basalt4 ,the limestone and dolomite were picked up by the glaciers from outcrops in northern ,illinois1 ,wisconsin1 and ,michigan4 ,some of the granite pebbles resemble outcrops in ,wisconsin2 others look like granite that crops out in ,canada4 ,the quartzite probably came from ,wisconsin1 and black shale fragments found in some gravel deposits came from the floor of ,lake ,michigan or from western ,michigan4 ,occasionally pieces of metallic copper are found that probably had their source in the ,lake ,superior copper-bearing area4 ,in addition to the sand associated with gravel deposits1 extensive deposits of sand alone are found at many places in ,illinois4 ,most of the sand grains are pieces of minerals that were constituents of rocks until weathering1 the grinding action of the glaciers1 and other erosive agencies broke the rocks into sand4 ,the principal mineral in glacial sand is quartz1 but many others occur in lesser amounts1 including calcite1 dolomite1 feldspar1 pyroxene1 tourmaline1 garnet1 magnetite1 and hornblende4 ,most of these are foreign to ,illinois1 although the calcite and dolomite may be native4 ,illustration3 ,figure #ah--,moraines left by ,wisconsinan glacier4 ,modified from ,george ,e4 ,ekblaw1 #aifj ,,illinois ,,state ,,geological ,,survey ,illustration3 ,figure #ai--;,gravel dredge1 with plant for processing the gravel in background4 ,uses of ,sand and ,gravel ,in #aifc more than #bg million tons of sand and gravel1 directly or indirectly of glacial origin1 was sold by ,illinois producers for almost #be million dollars4 ,the sand alone would have filled a child's sand box1 with an area of #h square miles1 to a depth of #a foot4 ,the gravel would have covered an even larger area4 ,the gravel was used in making concrete for roads and buildings1 for surfacing roads1 for ballast for railroad tracks1 and for other purposes4 ,the sand found its way into plaster1 mortar1 concrete1 and a variety of other products and uses4 ,some of it was produced for use as molding sand4 ,production of ,sand and ,gravel ,the production of sand and gravel from its deposits may be a relatively simple operation or one of considerable complexity4 ,gravel for surfacing a road may be dug from a conveniently located pit and loaded mechanically into trucks that haul it to the road4 ,a large sand- and gravel-producing operation1 however1 may include not only mechanical equipment to load and transport the material but also a processing plant where it can be washed if necessary and screened to various sizes4 ,in a 8dry pit0 operation1 mechanical cranes or shovels pick up the gravel and sand and load it into trucks1 railroad cars1 or conveyor belts to be transferred to the processing plant4 ,there clay and dirt may be washed out and the sand and gravel is sized by screens4 ,conveyor belts carry sand and gravel to the various processing operations and to storage bins or piles on the ground4 ,a 8wet pit0 operation produces sand and gravel from an artificial pond or lake4 ,in some operations the sand and gravel is mined by a dredge that floats on the water 7fig4 #ai74 ,in some pits1 a stream of water is directed from the dredge against the bank of gravel to wash the gravel into the lake4 ,a large metal pipe at the front of the dredge slants down into the water and sucks up the sand and gravel from the underwater part of the deposit4 ,the gravel1 sand1 and water is then pumped through a pipe at the rear of the dredge to the processing plant on the shore4 ,in some types of wet pit operations a large scoop or bucket operated from a crane on the shore1 or by cables fastened to the shore1 is used to dig sand and gravel from beneath the water4 ,dredges are used to pump up sand and gravel from the beds of ,illinois rivers1 especially the ,mississippi1 ,ohio1 and ,wabash4 ,the sand and gravel resources of many parts of the state have been mapped and studied by the ,illinois ,geological ,survey1 and work of this kind is continuing4 ,,silica 7,,tripoli7 ,,and ,,other ,,mineral ,,materials ,,of ,,extreme ,,southern ,,illinois ,the hills of extreme southern ,illinois contain several mineral materials that are entirely or largely restricted1 in important quantities1 to that part of the state4 ,some of them1 such as silica and novaculite1 come directly from bedrock deposits of great age2 others1 such as some of the sands and gravels1 are of more recent origin4 ,silica 7,tripoli7 ,a mineral material unique in ,illinois is the amorphous silica1 or tripoli1 mined in the hills of southern ,illinois about #bj miles north of ,cairo4 ,most of the silica mines are found at the heads of valleys or in tree-covered hill slopes along the less traveled roads4 ,an arched opening 7fig4 #bj7 with a road leading into it may be all that is visible of the mine from the outside4 ,inside are many rooms1 some #cj feet high1 separated by rounded pillars about #bj feet thick that have been left to support the arched mine roof4 ,most of the silica in the mines is white1 and this is the part that is mined4 ,a silica deposit is made up of layers--some of white1 powdery rock material1 others that look chalky but are firm or hard4 ,illustration3 ,figure #bj--;,entrance to a silica mine4 ,in the mines the silica is blasted loose from the natural deposit and loaded into trucks that take it to the processing mills at ,elco and ,tamms1 where it is crushed and then transferred to huge grinding mills that pulverize it to a very fine powder4 ,air currents of different velocities separate the powder into various grades of fineness1 and the finished silica goes into large paper bags for shipment4 ,origin of ,silica4--,some of the history of the formation of silica deposits is not fully known1 but it seems probable that their original character was quite different from what it is today4 ,investigations by ,survey geologists suggest that the parent rock formation was limestone and chert4 ,the limestone was composed of the mineral calcite1 but scattered through it were myriads of small particles of quartz4 ,interlayered with it were bands and beds of chert that contained varying amounts of calcite4 ,as the rocks above them were worn away by the ceaseless erosion of streams and rivers1 these original deposits were uncovered4 ,rain and snow-water then worked down into the limestone and chert deposits through cracks and crevices and dissolved the calcite in the rock4 ,the quartz remained because it is much less soluble than the calcite4 ,after many thousands of years all the calcite had been removed1 leaving behind a 8skeleton0 of quartz--the silica deposits of today4 ,uses of ,silica4-,the silica mined and milled in southern ,illinois has many uses4 ,a superfine grade1 known as white rouge1 is used to polish optical lenses4 ,other grades are used in scouring compounds1 metal polishes1 paints1 electrical resistors1 high-temperature pipe coverings1 fiberglass manufacture1 plastics1 silicone rubber1 wood filler1 caulking compounds1 ceramic products1 floor tile1 billiard cue chalk1 as foundry parting or facing1 concrete admixture1 in the manufacture of buffing compounds that are used to polish metal objects1 and for other purposes4 ,industry uses many thousands of tons of silica each year4 ,chert and ,chert ,gravel ,deposits of chert1 chert gravel1 and ganister also are among the variety of mineral materials found in extreme southern ,illinois4 ,chert consists principally of minutely crystalline particles of quartz4 ,some chert is popularly called flint4 ,in southern ,illinois chert occurs in two principal kinds of deposits1 those composed of solid ledges and those consisting of gravel4 ,the term novaculite is used in southern ,illinois for those solid deposits that are white1 comparatively thick1 and free of other interlayered materials4 ,no novaculite is mined at present1 but it is said to have been sold in past years for making sodium silicate and silica brick4 ,the chert gravels of southern ,illinois are of three kinds--novaculite gravel1 ,elco gravel1 and 8,lafayette0 ,gravel4 ,the novaculite and ,elco gravels consist of fragments of chert plus lesser amounts of fine silica particles and clay4 ,the chert fragments of the novaculite gravel are angular1 but the ,elco gravel includes both angular and rounded fragments4 ,these gravels are white1 yellow1 brown1 or reddish brown1 the novaculite gravel usually being the more highly colored4 ,deposits in ,union and ,alexander ,counties have been used for road surfacing and other purposes4 ,deposits of chert gravel also occur in ,hardin and ,saline ,counties1 and some stream valleys in southern and western ,illinois also contain such gravel4 8,lafayette0 ,gravel consists principally of brown chert pebbles4 ,most of the pebbles are rounded and have a smooth1 semi-polished surface4 ,the sand and clay occurring with the gravel are brown or dark red4 ,in some places there are deposits of coarse1 red quartz sand4 ,the gravel is most abundant in the four southernmost counties of the state1 and deposits may be as much as #fe feet thick4 ,it is used principally as a road-surfacing material4 ,ganister ,ganister occurs in the hills of ,alexander and ,union ,counties and is a loosely consolidated1 granular material consisting of irregular particles up to about an inch in diameter or of masses of material readily disintegrated into such particles4 ,the particles are composed mainly of fine crystalline quartz4 ,ganister is white1 cream1 light yellow1 or red and occurs in deposits up to #be feet or more thick4 ,relatively small tonnages of the light colored ganister are now used1 principally in making refractories1 but ganister is said to have been more widely used in that field in the past4 ,it is produced from underground mines4 ,some red ganister1 or ganister like material1 mined from open pits has been used for road surfacing4 ,studies of ,southern ,illinois ,materials ,survey geologists have mapped the chert- and silica-bearing formations of ,alexander and ,union ,counties and also many of the various kinds of gravel deposits4 ,samples have been tested to determine their chemical composition and the size of the particles composing them4 ,laboratory studies by ceramists indicate that novaculite and novaculite gravel1 when suitably processed1 can be used for making silica brick1 which withstands great heat4 ,canister and the gravels of southern ,illinois offer a variety of raw materials awaiting increased industrial use4 ,sands of ,extreme ,southern ,illinois ,in southern ,illinois deposits of sand laid down in an arm of the ocean that once extended northward into ,illinois from the ,gulf of ,mexico are found in ,alexander1 ,union1 ,pulaski1 ,pope1 and ,massac ,counties4 ,the deposits are commonly a light color--white1 cream1 yellow1 or gray4 ,the grains of the sand are almost all quartz and generally are angular4 ,some of the sands are of almost powder-like fineness1 others are fine or medium grained4 ,many of the sands contain flakes of white mica1 a glistening1 silvery-looking mineral often mistaken for silver or platinum4 ,unlike these metals1 however1 mica is comparatively light in weight and is not metallic4 ,also present in some sands are small flakes of the mineral graphite4 ,the southern ,illinois sands have not been widely used1 but some of them have been employed in making concrete4 ,they also may have possibilities for molding and core sand4 ,as a result of work by ,survey geologists1 the location and properties of many of the southern ,illinois sand deposits are known4 ,,clay ,,and ,,shale ,man has used clay in various ways for many hundreds of years4 ,from it he made1 and still makes1 bricks to build his dwellings1 pottery utensils of many kinds1 and other useful products4 ,everyone knows what clay is1 yet it is a substance difficult to define4 ,all clays are earth materials1 most of them plastic or sticky when wet but firm when dry4 ,if heated sufficiently 7fired7 they become hard4 ,clays are composed of various minerals4 ,of these1 the so-called clay minerals--complex substances composed mostly of alumina1 silica1 and water--generally are the most important4 ,they impart the property of plasticity and also cause clays to become hard when fired4 ,most clays are what geologists call unindurated 7unhardened7 rocks4 ,clay that has been indurated and occurs in layered deposits is commonly called shale4 ,the layers may be from a fraction of an inch to several inches thick4 ,most ,illinois shales are not plastic when dug from freshly exposed deposits1 but they become plastic when crushed and kneaded with water4 ,the clays and shales of ,illinois are the basis of a huge and important industry4 ,early ,uses in ,illinois ,clays and shales are useful because they can be made plastic by adding water1 formed into desired shapes1 and fired to a rock like hardness4 ,as a result1 various kinds of bricks1 drain tile1 pottery1 and other useful products are made from them4 ,in its early years1 ,illinois had many widely distributed potteries that used clay from nearby deposits to make a variety of jugs1 crocks1 and bowls that served in place of many present-day glass or metal articles4 ,drain tile has been of major importance in the development of the state4 ,early settlers found many low lying1 swampy areas and tracts of land that drained poorly after heavy rains4 ,ditches were dug to carry away the water from some areas1 but others were drained by means of drain tile--pieces of fired clay pipe several inches in diameter and about a foot long that were laid end to end in trenches below plough depth and then covered with earth4 ,water seeped into the tile1 which discharged it into ditches4 ,tile factories1 built throughout ,illinois near clay or shale deposits1 did an active business4 ,gradually1 however1 as more and more farm land was drained the demand slackened and many tile factories went out of business4 ,although there are fewer factories1 much drain tile is still manufactured in ,illinois4 ,many of the early tile plants also made bricks to be used for making foundations1 buildings1 sidewalks1 and other structures4 ,the bricks were made by hand-operated equipment4 ,some of the old hand-molded bricks may still be seen in older buildings4 ,now the brick-making process is highly mechanized and even though there are fewer plants they produce more bricks4 ,clay and ,shale ,deposits ,illinois shales are a part of the bedrock--that is1 they are associated with indurated rocks such as sandstone and limestone4 ,most clays are surficial rocks occurring in deposits near the surface1 where they lie above the bedrock4 ,exceptions are certain clays found in extreme southern ,illinois and the underclays1 also called fireclays1 that occur beneath coal seams and are part of the bedrock4 ,the surficial clays are of two principal kinds--till and loess4 ,till is a deposit left by glaciers4 ,it is a gray1 blue-gray1 or brown clay containing varying amounts of sand1 pebbles1 cobbles1 and even boulders4 ,till is found at many places in the state and is used for brick making1 especially in the ,chicago area4 ,loess is a wind-deposited silty clay or clayey silt and is found in many parts of ,illinois4 ,it is thickest on or near the bluffs of the ,mississippi1 ,illinois1 and ,ohio ,rivers4 ,it generally is brown and stands in steep faces in roadcuts and other excavations4 ,it once was widely used for making brick and tile4 ,of major importance in making clay products in ,illinois are the bedrock shales and the clays associated with the coal-bearing rocks that underlie much of the state4 ,the shales1 and the clays to a lesser extent1 are dug at many places for making structural clay products such as bricks1 structural tile1 and drain tile4 ,they also are used to make lightweight aggregate for concrete4 ,the underclays of some of the older coal seams are used to make buff-colored brick1 stoneware1 and a highly heat-resistant brick 7firebrick7 that is used in industrial furnaces or in other operations involving high temperatures4 ,some fireclay1 ground as fine as flour1 is added to molding sand to make it coherent enough to form into molds for metal casting4 ,sewer pipe and flue lining also are made from underclays4 ,clays unlike those found elsewhere in the state occur in extreme southern ,illinois4 ,one of these has the property of removing color from oils and was so used at one time by petroleum refineries4 ,another1 kaolin1 was extensively used during ,world ,war ,i for making crucibles4 ,clay ,minerals ,the uses of clay and shale are determined to a large degree by the properties of their clay minerals and to a lesser degree by the impurities present4 ,a clay or shale containing the clay mineral illite1 and other similar but less important clay minerals1 commonly becomes red when fired and gets hard at a relatively low temperature4 ,it therefore is used to make red bricks1 drain tile1 building tile1 and other structural clay products4 ,another clay mineral1 kaolinite1 generally burns to a light color and is difficult to fuse4 ,therefore1 clays composed wholly or mainly of kaolinite can be used for making buff or light-colored bricks and for the manufacture of highly heat-resistant 7refractory7 bricks4 ,the clay mineral in the southern ,illinois clay that was used to decolorize oil is montmorillonite4 ,this clay is now used in sweeping compounds1 as an oil absorbent1 as animal litter1 and for other purposes4 ,studies of ,clay and ,shale ,in view of the significant relationship between the clay minerals and the utilization of the clays and shales in which they occur1 the ,illinois ,geological ,survey has investigated extensively the clay minerals in the clay and shale deposits of ,illinois4 ,many samples were studied by means of powerful microscopes1 ,x-ray1 and chemical analysis4 ,most of the surface clays and shales proved to be composed principally of illite or related minerals4 ,the kaolin clay of extreme southern ,illinois contains the mineral kaolinite4 ,the older underclays also contain kaolinite1 but many of them also contain smaller amounts of illite4 ,the ,survey also has tested many clays to determine their burning properties and color when fired1 and hence their potential uses4 ,the bonding capabilities of other clays have been measured to find out whether they can be used as a bonding material for molding sand4 ,the bloating properties of ,illinois clays and shales from many deposits have been studied to determine which are suitable for making lightweight aggregate for the manufacture of concrete4 ,the object of these studies has been to discover the location1 character1 and possible uses of the state's clay and shale resources4 ,special studies are continuing in several parts of the state4 ,illinois is well endowed with clays and shales that can be used for a variety of purposes and has resources to fill future as well as present needs4 ,how ,bricks ,are ,made ,conversion of ,illinois clays and shales into useful products is an interesting process and is exemplified by the making of building bricks4 ,mechanical shovels dig the clay or shale and load it into trucks or small railroad cars that take it to the brick plant4 ,there1 machines grind the raw material and mix water with it until it has the consistency of stiff mud4 ,next1 a machine1 which operates somewhat like a meat grinder1 extrudes a brick-sized column of clay4 ,as the column moves forward1 it is automatically cut into bricks by wires4 ,the bricks are then dried in large heated rooms4 ,illustration3 ,figure #ba--;,beehive brick kiln4 ,from the driers1 the bricks go to huge ovens 7kilns7 and are heated until they are hard and have attained the desired color4 ,this is known as firing or burning the bricks4 ,temperatures employed are rarely lower than #ahjj ,f4 ,three kinds of kilns are used in ,illinois for burning bricks--beehive1 tunnel1 and scove4 ,a beehive kiln 7fig4 #ba7 has a round base and a dome-shaped top and somewhat resembles an oversized beehive4 ,unfired bricks are stacked in the kiln and the doors are sealed with burned bricks and clay4 ,fires are started in hearths or fire boxes in the wall of the kiln and the heat is circulated into and through the kiln4 ,it usually takes several days to fire the bricks adequately and let the kiln cool so that the bricks can be removed4 ,tunnel kilns1 made from heat-resistant bricks1 are actually tunnels big enough for a man to stand in4 ,the unburned bricks are loaded on flat steel cars on top of a layer of refractory blocks that protect the steel from the heat4 ,the cars enter the kiln and heating begins4 ,as they move through the kiln1 they carry the bricks through a firing area1 then through a cooling zone1 and finally out into the air4 ,in some brickyards in the ,chicago area1 dried unburned bricks are carefully stacked by machines into piles about #ag feet high1 #ce feet wide1 and #aae feet long1 which are known as scoves or scove kilns4 ,a layer of burned bricks that is plastered with clay covers the sides of the scove4 ,a jet of flame is directed through small tunnels at the base of the scove1 and the heat fires the bricks4 ,during #aifc1 more than #cbe1jjj1jjj bricks were produced by ,illinois brick plants4 ,in the same year1 the value of all the clay and clay products produced in ,illinois was nearly #ed1jjj1jjj4 ,besides brick and drain tile1 the products of the clay and shale industry of ,illinois include refractory brick1 building block and tile1 fire-proofing1 sewer pipe1 flue liners1 stoneware1 lightweight bloated burned clay aggregate for concrete1 and a variety of unburned clays for special purposes1 including bonding clay1 refractory fireclays1 absorbent for use on garage floors1 and litter for animal cages4 ,,peat ,after the retreat of the last of the great ice sheets from ,illinois1 numerous ponds and lakes were left in northern ,illinois1 especially in the eastern section4 ,some of them were soon drained by natural processes1 but others remained4 ,in the shallow water along their shores grew various plants1 chiefly reeds and sedges and1 locally1 a variety of moss4 ,as the plants died1 their partially decomposed remains were preserved beneath the water4 ,ultimately1 the ponds and lakes were overgrown and more or less completely filled by the plants and their remains1 giving rise to peat 7fig4 #bb7 bogs4 ,some peat bogs have been drained and are now used as farm land4 ,others remain and a few of them are the source of peat or humus for horticultural purposes4 ,producing operations are located in northeastern ,illinois and in ,whiteside ,county in northwestern ,illinois4 ,,other ,,mineral ,,resources ,in the future1 new uses will be made of the ,illinois industrial minerals already discussed4 ,in addition1 other mineral resources of the state that are not now being used may be the bases of new mineral industries4 ,some of these minerals are at present too costly to mine because the deposits are deeply buried or are not sufficiently rich to be worked at a profit4 ,others are not convenient to markets1 and still others have no present commercial use4 ,in years to come1 however1 changes may occur that will make it practical to mine1 process1 and use some of these resources4 ,furthermore1 some other mineral deposits that are now being utilized in a limited way may have greater future use4 ,the ,illinois ,geological ,survey continues to study the location1 character1 and composition of many such mineral materials and is alert for the development of new uses4 ,some of the materials are discussed briefly below4 ,illustration3 ,figure #bb--,peat from ,kane ,county showing its fibrous nature and remains of plants4 ,gypsum and ,anhydrite ,gypsum is a mineral that consists of calcium sulfate plus two molecules of water 7,ca,s,o#b;,h,o74 ,by suitably heating it1 the amount of water can be reduced1 and a product called calcined gypsum 7plaster of paris7 results4 ,this material changes back to gypsum if mixed with an appropriate quantity of water4 ,the ability of calcined gypsum to 8set0 when water is added makes it important in the manufacture of a variety of plasters and related products1 especially building materials4 ,gypsum also is used in cement making and in agriculture4 ,anhydrite 7,ca,s,o7 is like gypsum except that it contains no water and hence cannot be made into plaster of paris4 ,its uses are limited in the ,united ,states4 ,wells that were drilled for oil1 water1 or coal have encountered gypsum and_/or anhydrite in some parts of south-central ,illinois1 but the gypsum and anhydrite are not known to crop out at the surface4 ,a study of diamond drill cores and well cuttings on file at the ,survey showed that the shallowest gypsum and anhydrite reported occurred at a depth of #dgj feet in ,madison ,county4 ,the greatest continuous thickness of gypsum found was #b feet2 but in one well1 over #f feet of strata was penetrated that averaged almost #ge percent gypsum4 ,it is possible that thicker deposits of gypsum might be found if drilling were done especially in search of it4 ,feldspar-,bearing ,sands ,feldspar is the name applied to a group of minerals that are mainly silicates of potassium1 sodium1 and calcium4 ,various kinds of feldspar are used industrially in making glass1 enamels1 pottery1 and other products4 ,all the feldspar now used in ,illinois is shipped into the state4 ,the discovery by the ,illinois ,survey that some ,illinois sands contain considerable feldspar led ,survey geologists and chemists to find where deposits highest in feldspar occur1 what kinds of feldspar they contain1 and whether it could be separated from the sand in which it occurs4 ,beach sands1 river sands1 dune sands1 and sands from other kinds of deposits were studied4 ,it was found that many sands contain more than #ae percent feldspar and some as much as #be percent4 ,means of separating the feldspar from the sand are believed to exist1 but problems relating to the purity of the separated spar remain to be solved4 ,brines ,no salt is now produced in ,illinois1 but at one time the state was a major salt producer4 ,salt works were in operation near ,equality1 ,central ,city1 ,murphysboro1 ,st4 ,john1 ,danville1 and possibly other places4 ,the salt was obtained by evaporating salt water 7brine7 that came from natural springs or from wells4 ,the ,equality area was a particularly important producer of salt in the #ahjj's4 ,discovery elsewhere in the ,middle ,west of deposits of rock salt and brines that contained more salt than those of ,illinois is said to have been responsible for the discontinuance of salt making in the state4 ,no salt beds crop out in ,illinois1 nor are any known to have been encountered in the many wells that have been drilled for coal1 oil1 or water4 ,however1 most oil well drilling encounters brines containing various amounts and kinds of salts1 including the common table salt1 sodium chloride4 ,for reasons relating to the production of oil1 ,survey geologists and chemists have collected and analyzed many samples of ,illinois oil field brines1 and data are therefore available on their salt content4 ,no commercial use is being made of the brines as sources of salt4 ,oil ,shale ,illinois has a large oil-producing industry that obtains oil from wells4 ,the state also contains beds of shale that yield oil when the shale is heated4 ,in order to estimate the present and future importance of the oil shale resources1 the ,survey collected and tested more than #ajj shale samples from #da ,illinois counties4 ,a few samples contained more than #be gallons of oil per ton of shale1 but most contained less than #ae gallons per ton4 ,a study of the crude oil distilled from selected shale samples showed it to be somewhat different from the oil that comes from wells4 ,it could1 nevertheless1 be made to yield gasoline1 fuel oil1 and other products if suitably processed4 ,the shale strata generally the richest in oil are found above coal seams1 are black1 and are sometimes called slate by coal miners4 ,they are rarely more than #c feet thick1 but they extend over large areas4 ,sandstone ,sandstone has a long history of use in ,illinois4 ,pioneers built foundations for their houses and barns and curbs around their wells from it4 ,slabs of sandstone were once a popular material for sidewalks1 some of which are still in use4 ,churches and other sizable buildings have been constructed from it1 and at one time an ,illinois sandstone was used to make grindstones4 ,except for the ,st4 ,peter ,sandstone1 which was discussed under 8,silica ,sand10 the use of sandstone has decreased1 although comparatively small quantities are still used as building stone4 ,most ,illinois sandstones may be thought of as a mass of sand whose grains are more or less firmly cemented together by clay1 iron oxide1 and quartz1 either singly or in combination1 or1 less commonly1 by calcite4 ,the grains are particles of various minerals1 but most of them are quartz4 ,sandstones are especially common in the hill country of extreme southern ,illinois4 ,the ,survey's investigations in this area revealed that if they are suitably processed some of the sandstones may have possibilities for commercial use4 ,sandstones in other parts of the state also have been studied1 with similar conclusions4 ,barite ,barite 7barium sulfate1 ,ba,s,o7 is a deceptive mineral--it is much heavier than it looks4 ,barite found in ,illinois is generally white or light colored1 and1 although some of it looks rather like white limestone1 it is more than half again as heavy as limestone4 ,barite's unusual weight is responsible for one of its major uses--as a constituent of drilling muds for the oil industry4 ,these muds are a mixture of clay1 water1 and a weighting material such as barite4 ,they are used in various ways in the drilling of oil wells by rotary drills4 ,barite also is an important raw material for the manufacture of chemicals4 ,barite is found in ,hardin and ,pope ,counties1 the site of the fluorspar industry4 ,according to studies made by ,survey geologists1 the barite occurs both as veins and beds associated with fluorspar1 but its distribution is irregular and the deposits are of limited size4 ,a barite mine is said to have been worked years ago1 and more recently comparatively small tonnages have been taken from open pits4 ,future exploration in southern ,illinois may reveal deposits of barite that will be profitable to mine4 ,greensand ,in some parts of ,illinois occur sands or sandstone that contain numerous grains of the green mineral glauconite4 ,if the sands are not discolored by iron compounds or other substances1 they too have a greenish color and1 therefore1 are called greensands4 ,glauconite varies in composition but contains potassium1 magnesium1 iron1 aluminum1 silicon1 and water4 ,greensand is said to be used in relatively small amounts as a soil conditioner and as a water-softening agent4 ,greensand is known to occur in the general vicinity of ,olmsted in southern ,illinois4 ,near ,oregon in northern ,illinois an old quarry exposed #aj feet of greenish brown sandstone that contains glauconite4 ,samples from southern ,illinois and from the sandstone at ,oregon contained more than #f percent potassium oxide4 ,marl ,in some of the lakes and ponds left by the glaciers lived numerous small mollusks with calcium carbonate shells4 ,as the animals died1 their shells formed a deposit on the bottom of the lakes and ponds4 ,certain plants1 especially algae1 may have added a mudlike precipitate of calcium carbonate to the deposits1 and varying amounts of clay washed from the shores mixed with both these materials4 ,the resultant deposit is called marl4 ,some marl deposits have peat mixed with them1 and peat also overlies some marl deposits4 ,only comparatively small amounts of marl are known to have been dug in ,illinois4 ,one deposit containing many shells and shell fragments1 some of it associated with peat1 was worked in southeastern ,livingston ,county as a source of agricultural liming material4 ,other deposits have been reported at other places in northeastern ,illinois4 ,the available information indicates that the marl deposits are likely to be principally of local importance4 ,tufa and ,travertine ,the tufa 7fig4 #bc7 and travertine occurring as surficial deposits in ,illinois were formed by springs4 ,the deposits usually occur at or near the outcrop of a layer of porous water-bearing earth material1 such as gravel1 sandstone1 or fissured limestone1 that is underlain by a nonporous clay or shale formation4 ,water moving down through the porous layer cannot sink through the clay or shale and so is forced to move laterally4 ,where valleys have cut into the layers of gravel or rock1 the water emerges as springs4 ,if the material through which the water has passed is limestone1 or gravel containing limestone as most ,illinois gravels do1 some of the limestone is likely to have dissolved in the water4 ,when the water issues as a spring1 conditions may be such as to cause precipitation of the dissolved limestone as tufa or1 more rarely1 travertine4 ,tufa is generally highly porous and more or less impure1 whereas travertine is harder and less porous4 ,the middle or lower slopes of bluffs are common sites for spring-deposited tufa or travertine4 ,deposits have been seen in various parts of ,illinois1 but are not known to have been worked1 except in ,calhoun ,county where small quantities of tufa were produced for use as agricultural limestone4 ,it is thought that the tufa and travertine deposits of ,illinois are relatively small1 but they may be of local importance4 ,illustration3 ,figure #bc--;,calcareous tufa from ,pike ,county4 ,in addition to the large visible pores there are numerous tiny ones4 ,pyrite and ,marcasite ,the mineral pyrite consists of iron and sulfur as the compound iron sulfide 7,fe,s7 and1 because of its shiny1 brassy yellow color1 is sometimes called fool's gold4 ,marcasite has the same composition as pyrite1 but its crystals have a different shape and it is often lighter colored4 ,both minerals occur in various parts of the state2 they are particularly prevalent in some coal seams1 and when so occurring are in some cases called coal brasses or 8sulfur40 ,pyrite and marcasite are used commercially as raw materials for making sulfuric acid1 although sulfur itself is more extensively used for that purpose4 ,at one time coal brasses recovered during coal-cleaning operations at a northwestern ,illinois coal mine were sold for acid making4 ,a large quantity of coal brasses probably could be recovered from such operations at ,illinois coal mines4 ,uranium ,uranium has been sought in ,illinois by many people in recent years4 ,the ,geological ,survey also carried out a wide search for uranium and particular attention was paid to certain clays and other rocks in ,hardin ,county and certain black shales in other parts of the state4 ,about #bjj samples from ,hardin ,county and #age samples of the shales were tested by the ,survey4 ,no deposits were found that are known to be of the required richness and quantity4 ,iron ,ore ,about the middle of the #aith century two furnaces in ,hardin ,county in extreme southern ,illinois for a time produced iron from local limonite ores4 ,the ore is said to have occurred as pellets1 chunks1 and masses scattered through soil and clay and apparently was of irregular distribution4 ,little can be seen of the deposits today4 ,their extent is not known1 but they are believed to be of limited size4 ,the ,illinois ,state ,geological ,survey carries on a continuous program of research on the industrial minerals and metals of ,illinois and their uses4 ,in addition to the investigations mentioned in this booklet1 many others have been made or are in progress4 ,such studies are necessarily a continuing activity if the full potentialities of ,illinois mineral resources are to be realized1 for industry continually demands new raw materials and changes its requirements for those now used4 ,the ,survey has issued numerous reports that deal with the resources discussed here and mimeographed lists of these are available upon request4 ,if reproduction is made of the material herein1 acknowledgment of the ,illinois ,state ,geological ,survey is requested4 ,transcriber's ,notes --,silently corrected a few typos4 --,retained publication information from the printed edition3 this e,book is public-domain in the country of publication4 --,in the text versions only1 text in italics is delimited by underscores4