3.4. GS: , ^"jn ^ULi^t^j CIR /a«/ c a. WyAI ABOUT OUIRMDNERAILS? A QUIZ BOOK on the Geology and Mineral Resources of Illinois STATE GEOLOGICAL SURVEY CIRCULAR 124 STATE OF ILLINOIS WILLIAM G. STRATTON, Governor DEPARTMENT OF REGISTRATION AND EDUCATION VERA M. BINKS, Director DIVISION OF THE STATE GEOLOGICAL SURVEY JOHN C. FRYE, Chief URBANA PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 1946 REPRINTED 1947, 1948, 1952, 1954 3 3051 00004 667b GEOLOGY OF ILLI NOIS WHAT IS THE EARTH'S CRUST UNDER ILLINOIS MADE OF? It is made of rock, covered by a mantle of "earth." WHAT KIND OF ROCK? From l/2 to 2 miles down, there are mostly sandstones, shales, and lime- stones. These rocks lie in layers like the leaves of an old crumpled book. WHY ARE THESE ROCKS IN LAYERS? They originated beneath the surface of large bodies of water - often of the sea - as sediments such as sand, clay, or marl. These sheets of sediments spread widely across the bottom, layer upon layer. WHAT LIES UNDER THE SEDIMENTARY ROCKS? Avery much older and more complex mass of cry- stalline rock; much of this mass was once molten, and solidified to form rocks like granite and lava. HOW WAS THE COVERING MANTLE OF LOOSE MATERIAL FORMED? Most of this covering was formed during the Glacial period when, as the glaciers melted away, they left behind the "glacial drift" - pebbly clay, sand, gravel, and boulders - that had been picked up by the over-riding ice as it moved southward. WHAT ELSE HELPS FORM THE LOOSE MANTLE THAT COVERS THE BEDROCK? Besides the glacial drift, there are sands, clays, peat, and marl which were formed in the lakes, streams, and swamps that came as the ice melted. The wind also played its part in moving the loose material and depositing it again as "loess" (wind- blown silt) or as dune sand. These activities con- tinue to the present day. HOW WAS THE TOP-SOIL FORMED? Illinois' rich top-soil was formed from barren earth by the action of wind and rain, of bacteria and small animals, of plant growth and decay. HOW ABOUT SOILS WHICH WELL DRILLERS FIND DEEP BELOW THE SURFACE - WERE THEY FORMED IN THE SAME WAY AS THE TOP-SOILS? Yes, except that they were formed during a warm period between two glacial invasions and then were buried by the glacial drift of the later invasion. HAVE DINOSAURS EVER BEEN FOUND HERE? No. They probably roamed over the State, but the sediments in which their bones might have been buried and preserved were almost all eroded away ages ago. HAVE REMAINS OF OTHER LARGE EXTINCT ANIMALS BEEN FOUND IN ILLINOIS? Yes. The remains of Ice Age mammoths and mas- todons are sometimes found. Very much older are the giant salamander -like amphibians that come from the coal-bearing rocks; they are among the oldest four-footed animals. WHAT ARE THE OLDEST FOSSILS FOUND IN ILLI- NOIS? They are the remains of sea animals called "tri- lobites" and have been found in the Cambrian sand- stone at Oregon, Illinois. These early settlers are estimated to have lived here 450,000,000 years ago. UNDERGROUND WEALTH IS ILLINOIS RICH IN MINERAL WEALTH? Yes. It possesses two of the world's three most important minerals - COAL and OIL. The third, IRON ORE, is cheaply floated to Illinois down the Great Lakes from the world's richest iron ore re- gion, Minnesota and Michigan. WHAT IS THE DOLLAR VALUE OF ILLINOIS' MINERAL PRODUCTION? Illinois produces approximately $500,000,000 worth of mineral products each year. This, together with the minerals processed (but not mined) in Illinois, (such as pig iron, metallurgical coke, slab zinc, etc.) brings the total to about $900,000,000. HOW DOES ILLINOIS RANK AS A MINERAL PRO- DUCING STATE? Illinois is 1st in the Upper Mississippi Valley, 7th in the nation, and exceeds many nations of the world in mineral production. WHAT KINDS OF MINERAL PRODUCTS ARE PRO- DUCED IN ILLINOIS? Illinois produces a great variety of mineral pro- ducts. In order of value they are: Coal Oil and Natural Gas Limestone and Dolomite Whitewares and Pottery Fluorspar Cement Silica Sand Structural Clay Products Refractory Clay Products Gravel Lime Mineral Wool Zinc Sand Ground Silica Clay Fuller's Earth Lead Tripoli Ganister Silver (small amount) In a broad sense, soil is also largely a complex mineral substance, and in the scientific sense, so is water. ii HOW MANY PEOPLE WORK IN THE MINERAL INDUSTRY IN ILLINOIS? Approximately 35,000 work in the mines, quarries, and oilfields, and another 20,000 in the processing plants. Multiply these figures several times to in- clude the people who transport the materials, work in the offices, and are members of the families so engaged, and you will see that a large section of the State earns its living from mineral production. DOES THE ILLINOIS FARMER BENEFIT FROM THE PRODUCTION OF MINERALS? Indeed the farmer's position has been largely changed, through the use of mineral products, from a back-break- ing toiler of the soil to an engineer directing labor- saving machines. His new gas -driven mechanical slaves not only relieve his toil but enable him to increase his production. And to a greater or lesser extent, this same picture holds true for all other walks of life. IS THERE ANY DANGER THAT FOREIGN IMPORTS WILL THREATEN ANY OF ILLINOIS' MINERAL INDUSTRIES? No. Most of Illinois mineral products are those for which there is a world shortage. Others, such as sand, gravel, and stone are so bulky that they must be dug or quarried nearby. IN HOW MANY OF ILLINOIS* COUNTIES ARE MINERALS DUG, MINED, OR QUARRIED? Mines, quarries, pits, or oil or gas wells are lo- cated in at least 100 of the 102 counties of the State. COAL - MINERAL OF MIGHT HOW IMPORTANT IS COAL TO MANKIND? The greatest industrial districts, the wealthiest nations, and the strongest political powers are those where coal is abundant. The United States leads the world in coal production. HOW DOES ILLINOIS RANK AS A PRODUCER OF COAL? Illinois ranks 4th among the states. In the world picture, this single state also holds its own; it pro- duces more coal than any foreign nation except Ger- many, Russia, Great Britain, Poland, and France. WHERE IS ILLINOIS COAL USED? It is used to heat the homes, power the industries, and run the railroads of Illinois and of the rich Up- per Mississippi Valley states to north and west. Most of our coal moves by rail, a smaller amount by river barge and lake freighter. HOW MUCH COAL IS MINED IN ILLINOIS EACH YEAR? Since World War II, an average of about 55,000,000 tons, worth over $200,000,000 per year. WILL ILLINOIS COAL VEINS SOON BE EXHAUSTED? It would take well over 1,000 years at present rate of mining to exhaust Illinois coal. It is estimated that about 135,000,000,000 tons of mineable coal still remain beneath the surface of the State. HOW MANY COAL BEDS ARE THERE IN ILLINOIS? There are 25 to 30, but only 6 are worth mining un- der present standards. ARE ILLINOIS COAL MINES USING MODERN MACHINERY? Yes. The "Coal Reports of Illinois" show that the State is far in advance in using modern mining meth- ods, and the amount of coal a man can mine a day- has risen year by year. This means more and cheaper coal for the consumer, and more wages and profits for miner and operator. WHAT IS A "STRIP MINE" ? A strip mine operates at the surface by removing, or "stripping," the overburden which covers the coal vein. WHAT DO WE GET FROM COAL BESIDES HEAT AND POWER? So many things, with new discoveries every day, that no one can count them accurately. Most important Wood preservatives like creosote Tar -like paving and roofing materials / Special fuels and solvents \ 1 I I / Chemicals used in making medicines and drugs like aspirin and the sulfa drugs \ ' N ^x~^ N / / Artificial rubber \ \\ Perfumes, flavors, dyes Explosives (>' \\ During World War II Germany\ depended' on coal for making nearly all its gasoline; so far, it has not been necessary to go to coal for gasoline in America. ' HOW DID ILLINOIS COAL BEDS FORM? Coal originated from plants that lived a very long time ago when the sea coast lay not far west of the Mississippi River, and Illinois was a low coastal plain. This plain was covered with great swamps in which the leaves, seeds, spores, and branches of the dense vegetation accumulated to form thick peat- like masses. These half rotten masses, after a long time, were covered by sand and mud washed from higher land. Then as the land sank, a new swamp formed, a new peat bed accumulated, and again was covered by mud and sand. This happened many times, and in the end, the layers of peat, mud, and sand accumu- lated to a depth of several thousand feet. This mass slowly hardened, the sand and mud be- came bedrock and the peat became coal. HOW DO YOU KNOW THAT COAL ORIGINATED FROM PLANT REMAINS? Sometimes plant impressions or fossilized wood can be seen right in the coal; often the roots and the stumps of the trees of the Coal Forest are still preserved in the clay just below the coal bed. A coal, when specially prepared and studied under the microscope, is revealed to be full of small bits of carbonized vegetation. OIL-- GIFT OF ANCIENT SEAS WHAT MAKES OIL? Ages ago, when the sea covered Illinois, large num- bers of animals and microscopic plants lived and died here, and were buried in the marl and mud at the bottom of the sea. As these layers of mud and marl slowly hardened into bedrock, they remained saturated with saltwater. Meanwhile, the buried animal and plant matter was slowly changing into oil and gas. Oil and gas are lighter than the salt water. Bit by bit, they separated from the water and moved into the highest places in the more porous rock layers, just as cream comes to the top in milk. -$r HOW CAN A PERSON TELL WHEN OIL IS ftd PRESENT UNDER A PIECE OF LAND? _j|p___. Only by drilling can you be certain that oil is present in commercial quantities. But by careful geological study you can find the most favorable place to drill. This can be done only by studying the position of the bedrock layers; the surface hills and valleys have nothing to do with the question. Because the oil and gas move upward above the salt water, the geologist tries to find the high spots in a porous rock layer. To get this information, he stud- ies rock layers at the surface, and sounds the depths of the earth with special geophysical instruments. ARE THERE LAKES OF OIL UNDERGROUND ? No, the oil occurs in small pores between the grains of coarser types of ordinary sandstone or limestone and in fractures, crevices, and partings, through rwhich subterranean pressures drive it into the well. HOW DOES ILLINOIS RANK IN OIL PRODUCTION? It ranks 8th among the states. But when we com- pare this single state with the nations of the world it is exceeded only by Venezuela, Russia, Iraq, Saudi Arabia, Kuwait, Mexico, and Canada. It produces more oil than all of Western Europe or about as much as strategic Indonesia. HOW LARGE AN OIL PRODUCER IS ILLINOIS? Illinois produces about 60 million barrels of oil each year, worth over $170,000,000. HOW MANY OIL FIELDS HAS ILLINOIS? There are over 350 producing fields in Illinois, consisting of nearly 30,000 wells. The deepest producing well is 4,600 feet. WHAT IS THE BIGGEST OIL WELL ILLINOIS EVER HAD? A well near Centralia produced about 12,000 barrels of oil in the first 24 hours. IS OIL PRODUCTION IN ILLINOIS INCREASING OR DECREASING? At present it is decreasing, but only very slowly because small new fields are being continually dis- covered. The State will be an important oil pro- ducer for many years to come. 10 FLUORSPAR VERSATILE SERVANT OF INDUSTRY WHAT IS FLUORSPAR? Fluorspar is an attractive mineral, as hard and lustrous as glass, commonly an amethyst color but also white, yellow, blue, green, brown, or black. It is made up of calcium and fluorine. Some varie- ties glow in invisible ultraviolet light, this property is named "fluorescence," after the mineral. HOW IS FLUORSPAR USED? A large portion is used in the iron and steel industry as a flux. Hydrofluoric acid, made from fluorspar, enters into the preparation of many chemicals, in- cluding those which play a part in the manufacture of high-octane gasoline, refrigerants, plastics, and insecticides. Fluorspar and compounds made from it are used in making glass and enamels, and in the aluminum industry. HOW MUCH FLUORSPAR IS MINED IN ILLINOIS? About three -fourths of the fluorspar mined in the Western Hemisphere has come from a small area in Illinois and Kentucky. Illinois produces the larg- er share — about $8,000,000 worth annually. WHERE DOES OUR FLUORSPAR COME FROM? It is mined from veins as much as 800 feet deep, in Pope and Hardin counties. LEAD - ZINC - SILVER WHERE ARE LEAD AND ZINC ORES MINED IN ILLINOIS? In the extreme northwest corner (Jo Daviess Co.) and in the southeast corner (Pope and Hardin Cos.) where they occur with the fluorspar deposits. WHAT ARE LEAD AND ZINC ORES LIKE? Lead ore is a mineral called galena, which is a combination of lead and sulfur. It is very heavy, dark gray, and breaks into shiny square-sided pieces. Zinc ore is chiefly a mineral called sphalerite (black jack or blende), which is made of zinc and sulfur. It is less heavy than galena, has a resinous lustre, and may be brown, black, or yellow. HOW IS LEAD and ZINC EXTRACTED from ORE? The ore is ground up in a stamp mill, then separa- ted from lighter rock and mineral impurities by shaking on a jig table or by flotation in acid bubbles. Then the concentrated ore is roasted at a smelter to drive off the sulfur. Most of the Illinois ore is free from the stubborn impurities so common in many lead-zinc ores. HOW LONG HAS LEAD BEEN MINED IN ILLINOIS? The lead deposits of northwestern Illinois were known to French explorers over 250 years ago and have played an important part in Illinois history; until fairly recent times the zinc was thought to be of no value. In southeastern Illinois, lead mining^ began in 1842. /^ f~ IS THERE ANY SILVER IN ILLINOIS? Silver occurs in minute amounts with some lead-zinc ore in southeastern Illinois; $2,000 is produced yearly. HOW MUCH LEAD AND ZINC f ] ^ IS PRODUCED IN ILLINOIS? ( ^^ An average of about $6,000,000 worth has been produced annually since the war. STONE - PLAIN BUT DEPENDAB &£rt<$ ^^A WHAT KINDS OF STONE DOES ILLINOIS PRODUCE'? Mostly limestone and dolomite, but some sandstone is also quarried for rip-rap along streams and for foundations of small-buildings. In northeastern Illinois, homes and rock gardens are made from the colorful boulders from glacial deposits WHAT IS DOLOMITE? Dolomite is a kind of limestone that contains a lot of magnesia in addition to the lime and carbon di- oxide which make up ordinary limestone WHY ARE MOST LIMESTONE QUARRIES FOUND IN A RIM AROUND THE EDGES OF THE STATE? The limestone and dolomite layers crop out around the edges of the State and slope gently downward toward the middle of the State to form a great bowl called the Illinois Basin. This basin is floored by the deeply buried limestone layers and filled by the coal-bearing formations. ARE THERE MANY USES FOR LIMESTONE AND DOLOMITE? Yes, they have over 100 uses. Millions of tons are crushed for use in the great construction industry of the State, while large quantities go into making lime and cement, for agstone on the soil, and as a flux in the steel industry. The slag from the steel industry, in turn, is used in making mineral wool. WHAT IS MINERAL WOOL? Mineral wool is a grayish-white wooly fibre used in insulating walls and buildings. In Illinois it is made from blast-furnace slag which is melted and blown into thin "hairs" by high-pressure steam. WHERE IS CEMENT MADE IN ILLINOIS? Cement is made at three plants near LaSalle and one near Dixon. Over $17,000,000 worth is pro- duced annually. WHY IS AGSTONE (FIELD LIME) USED ON SOILS? The lime and magnesia in limestone and dolomite are alkalies which counteract acidity. They not only sweeten the soil but increase the humus and also the lime content of the crops. HOW DID PETRIFIED SEA SHELLS GET INTO ILLINOIS LIMESTONE LAYERS? Most Illinois limestone was formed ages ago in the bottom of the sea, which then extended far into the interior of the United States. In places, as near Chicago, there were even reefs full of corals. 14 SAND andGRAVEL - GIFT OF GLACIERS WERE THERE EVER TRUE GLACIERS IN ILLINOIS? Yes. In former times ice-sheets, like the one that covers Greenland, extended over Can- ada and northern United States. The ice - sheets moved down from the north not once, but several times, and between the glacial stages the weather was as warm as at present. Limits of Ice-Age Glaciers HOW LONG AGO WAS THE ICE AGE? The last ice-sheet disappeared from northeastern Illinois about 35,000 years ago. Geologists regard this as a very short time indeed, compared with the age of most rocks and geological events. DID GLACIERS HELP OR INJURE THE STATE? They enriched the State greatly. By smoothing out the hills and valleys and covering up most rough and rocky land, they built the rich agricultural prairie. Most of the gravel and sand, including the valuable natural -bonded molding sand, are glacial deposits, as is much of the clay used in industry. 15 WHERE DID THE GRANITE BOULDERS COME FROM-? Many of them came from Canada. The region near Lake Superior furnished both boulders and the huge masses of copper that are occasionally found. HOW DOES A GLACIER PRODUCE SAND AND GRAVEL? As the glacier moved along it picked up much of the material - clay, sand, and loose rock that lay over the ground. As the glacier melted, these earth ma- terials were washed out, roughly sorted, and de- posited in outwash plains and along valleys. WERE ALL THE SAND AND GRAVEL DEPOSITS IN ILLINOIS LEFT BY THE GLACIERS'? No. There are older chert (flint) gravels in ex- treme southern Illinois, where glaciers did not reach. Younger sands, that formed since the Ice Age, are dredged from the larger rivers and Lake Michigan. The silica sand comes from sandstone bedrock. HOW MUCH SAND AND GRAVEL DOES ILLINOIS USE? Annually some 15,000,000 tons are produced. Good gravel close by means cheap gravel, and cheap grav- el means more and better roads and other building projects. WHAT IS MOLDING SAND? Molding sand is very important in the metal indus- try, where it is used to form the molds into which the molten metal is poured. CAN ANY SAND BE USED AS MOLDING SAND? No. Molding sands must have special properties for different uses. They must have the right sur- face, they must not collapse when the heavy metal is poured into them, they must not melt and fuse, they must not burn out or sinter and become unfit for re-use. HAS ILLINOIS SPECIAL TYPES OF SAND FOR METAL MOLDING? It has many, but most outstanding is the silica sand which can stand very high temperatures in steel casting, and natural-bonded molding sand which can be used practically as it is dug, and does not have to be mixed with a binding substance. SILICA SAND AND SILICA WHAT IS SILICA SAND MADE OF? Most sands are tiny fragments of hard minerals that resist wear. Quartz (a natural form of silica) is the common sand mineral. Sands that are near- ly pure quartz are called silica sand. HOW IS SILICA SAND USED IN MAKING GLASS? The usual types of glass are made by melting to- gether a mixture of chemicals containing at least 2/3 silica sand. If impurities are present in the sand they may affect the quality, especially color, of the glass. HOW ELSE IS SILICA SAND USED? It is an important type of molding sand because it can endure the great heat of steel casting. Some is 17 ground as fine as flour, to be used for grinding powder, or in enamel, pottery, porcelain and tile, or as an ingredient in paint. WHERE DOES SILICA SAND COME FROM? Ottawa, in northern Illinois, is the silica sand cen- ter. Our State is fortunate, not only because of the purity of this deposit, but because it is handy to centers of industry. IS ILLINOIS AN IMPORTANT PRODUCER OF SILICA SAND? Yes. It leads the nation, and sold 2,367,000 tons for $5,438,000 in 1952. WHAT IS TRIPOLI? Tripoli is a name for southern Illinois "silica" and is made by grinding a white silica rock to a flour. It has a great many uses, mostly in paint, as fine grinding powders (including "white rouge"), in polishing compounds, and as an ingredient in concrete. HOW DOES ILLINOIS RANK IN TRIPOLI PRODUCTION? Illinois is one of the important producing states, and the value of the production is several hundred thousand dollars yearly. WHERE IS TRIPOLI MINED IN ILLINOIS? It comes from Alexander and Union counties at the southern tip of the State. 18 CLAY for INDUSTRY, HOME, and FARM WHAT KINDS OF CLAY DOES ILLINOIS HAVE? Fireclay, shale, surface clay, fuller's earth, and kaolin. ARE ILLINOIS CLAY DEPOSITS LARGE? Supplies of surface clay and shale are inexhaustible, fireclay and fuller's earth are abundant, but the quantity of kaolin is small, WERE ALL THE CLAYS FORMED AS A RESULT OF THE GLACIERS? No. The shale and fireclay exist as layers in the bedrock; the fireclay lies just below some of the coal beds. The kaolin and fuller's earth of southern Illinois were formed before the Ice Age, when the Gulf of Mexico extended as far north as the south tip of the State. WHAT ARE THE MAIN USES (y^iZ^^wJ FOR ILLINOIS CLAYS? Structural clay products - such as brick, drain tile, and hollow block are made from shale, fireclay, and surface clay. Fireclay is used as a bond to stick together mold- ing sand, to plaster the walls of industrial furnaces and to make refractory brick that can withstand the great heat in these furnaces and in the huge brick-lined ladles that handle molten metal. In your home, Illinois fireclay may have supplied the art pottery in the living room, the stoneware crocks in the kitchen, and the sewer pipes under the house. 19 Shale is mixed with limestone in cement making. Illi- nois kaolin is used for crucibles and for china and porcelain. Fuller's earth is employed for bleaching oil, as an oil and grease absorbent, and as a sweep- ing compound. HOW LARGE IS ILLINOIS' CLAY INDUSTRY? About $45,000,000 worth of clay products is pro- duced yearly, or about half the total of the Upper Mississippi Valley. WATERS UNDER THE EARTH HOW DEEP IS ILLINOIS' DEEPEST WATER WELL ?\ 2,800 feet deep, at Oglesby. / WHERE ARE MOST OF OUR DEEP WATER WELLS? ' Most of them are in the northern third of Illinois. WHAT IS GROUNDWATER? / f That part of the rainfall which sinks into the ground instead of running off in streams or evaporating. WHAT IS AN ARTESIAN WELL? ' The rain water may enter a porous rock layer that is exposed at the surface. If the rock layer slopes downward under ground, the water may follow down- to great depths and for many miles. Water seeks its own level. Therefore when a deep- ly buried porous layer is tapped by a well, the water moves far up the hole or gushes into the air. Such wells, including most Illinois deep wells, are called artesian. . WHAT KIND OF FORMATIONS YIELD GROUND- WATER? Deep wells that penetrate the bedrock may draw their water from layers of coarse sand- stone or porous limestone, or from zones full of fissures or crevices. Shallow wells get their water from porous sand or gravel beds. MINERALS and SCIENCE in ILLINOIS WHAT STATE AGENCY STUDIES THE MINERAL RESOURCES OF ILLINOIS? The State Geological Survey Division of the De- partment of Registration and Education. WHAT DOES THE GEOLOGICAL SURVEY DO? It makes physical and chemical analyses of useful rocks, minerals, and mineral products, develops techniques and methods for preparing mineral sub- stances for use, discovers new information con- cerning the naturally occurring mineral substances, conducts experiments to improve and find new uses for the minerals of Illinois, and publishes the re- sults of its field surveys and laboratory findings. HOW CAN THE PUBLIC RECEIVE THE BENEFITS OF THIS SCIENTIFIC WORK? The vast store of information in the open files of the Geological Survey is available to the public up- on request at all times. Its scientific and technical staff stands ready to serve by letter, telegram, or 21 telephone, by personal interview, or by sending publications, according to individual needs. WHAT IS THE COST OF ITS SERVICES? No charge is made for services except in cases requiring extraordinary labor. Publications are distributed free within the State for 60 days from date of issue, after which a small fee is charged for certain bulletins. HOW CAN I SECURE A LIST OF PUBLICATIONS ISSUED BY THE STATE GEOLOGICAL SURVEY? The Survey will be glad to send you free its list of publications upon request. Furthermore, any ques- tions you may have will be answered promptly, or referred to the proper office if they lie outside the Geological Survey's field. DOES the GEOLOGICAL SURVEY COOPERATE CLOSELY with the PUBLIC SCHOOL SYSTEM? Yes. The Geological Survey publishes popular and educational bulletins designed for the use of teach- ers and students; it distributes a labeled collection of rocks and minerals for class use; it conducts several geological field trips each year for science teachers in various sections of the State; and when possible it gives illustrated lectures on the geology and mineral resources of the State. IS THE PROFESSION OF GEOLOGY INCREASING IN IMPORTANCE? Yes. Our national life and welfare is dependent more and more upon the further discovery and the proper and best use of the natural resources of the Earth. Geology and allied sciences are being called 4/ upon increasingly to aid in a more intelligent and efficient discovery and use of mineral resources hidden in the Earth's crust. IS GEOLOGY DIFFICULT TO UNDERSTAND? No. The main ideas are easy to understand. Geology may seem difficult to the layman merely because of the technical vocabulary, which the ex- pert must use in order to get the fullest accuracy and precision. But the main facts and interesting highlights, when translated into everyday language, can increase anyone's enjoyment through acquaint- ance with the nature and history of the Earth. HOW does ILLINOIS RANK among OTHER STATES in GEOLOGICAL RESEARCH and SERVICE to the CITIZENS of the STATE? The State of Illinois is widely recognized by educa- tors, scientists, and industrialists as one of the most outstanding states in promotion of research and in the value of its information to aid its indus- trial development. ^ ^^''^ ffiff]- ^23 NOTICE TO TEACHERS The Geological Survey prepares sets of rocks, minerals, and fossils, for class use. WHAT ABOUT OUR MINERALS ? O