Part 4

HOW LONG WILL OUR COAL SUPPLIES LAST?

It will take well over 1,000 years at the present rate of mining in Illinois to exhaust our coal reserves. An estimated 140 billion tons of coal in seams of minable thickness remain in the ground in our state; these are the largest known reserves of bituminous coal of any state in the United States.

WHAT IS COAL USED FOR?

Electric power generation consumes the greater part of the annual coal production in Illinois. Coal is also used for home and commercial heating, for production of coke, and for manufacturing various chemical compounds from coal tar. Products derived from coal tar include drugs and medicines, plastics, synthetic fibres, perfumes, flavorings, dyes, synthetic rubbers, explosives, specialized oils, solvents, wood preservatives, tarlike paving and roofing materials, and some gas. The gas is both produced and utilized in the coke industry.

WHAT IS COKE?

Coke is a material produced by burning coal in the absence of air so that most of the gases and water are driven off without consuming the solid portion. The resulting solid coke is a strong, porous, combustible substance.

HOW IMPORTANT IS COKE AND HOW IS IT USED?

The structure and nature of coke make it a valuable fuel for blast furnace use in the production of steel. In the past, most of the coal used in the manufacture of coke has come from areas of higher quality coal outside of our state. However, at present, over 1,000,000 tons of Illinois coal are mined annually for the production of metallurgical coke.

Area underlain by coal-bearing rocks Counties producing coal in January 1965 Total Production 3,749,423,534 tons 71 counties producing

STONE AND STONE PRODUCTS

WHAT TYPES OF STONE ARE PRODUCED IN ILLINOIS?

Limestone and dolomite are the most abundant rocks quarried in Illinois. Small amounts of marble, limestone, and sandstone for building stone are also produced. In addition, some glacial boulders and cobbles are used for rock gardens and in home construction. The crushed limestone industry is Illinois’ most important rock products industry.

WHAT ARE LIMESTONE AND DOLOMITE?

Limestone is a sedimentary rock that consists chiefly of calcite, which is composed of calcium, carbon, and oxygen. Dolomite is a variety of limestone that contains considerable magnesium in addition to the other elements. Limestones were deposited on the floors of ancient seas that repeatedly covered most parts of Illinois. Shelled creatures, corals, and coral reefs helped build up the thick limestone deposits (figs. 13 and 14).

WHERE ARE LIMESTONE AND DOLOMITE QUARRIES LOCATED IN ILLINOIS?

Limestone and dolomite quarries are located along the southern, western, and northern margins of the state where the thick deposits of these rocks crop out at the surface. Although bedrock was deposited in horizontal layers, it has since been downfolded into the Illinois Basin whose center is in southeastern Illinois. Thus, the thick limestones and dolomites that are quarried along the margins of the state are too deeply buried to be quarried in the central part of this basin (fig. 15).

Strophomena 1× Paleoneilo 1× Ctenodonta ⅔× Dolmanites ½× Archimedes 1× Hormotoma Polygyra 1× Mucrospirifer 1½× Atrypa ⅔× Crinoid Columnais 1× Halysites ⅔× Hexagonaria 1× Microcylus 1× Streptelasma ⅔× Lithostrationella ½× Lophophyllum 1×

MISS. RIVER Waterloo Mt. Vernon ILLINOIS WABASH RIVER INDIANA New Albany OHIO RIVER

ARE ANY STONE QUARRIES LOCATED IN THE AREA UNDERLAIN BY THE ILLINOIS BASIN?

Yes. In the area underlain by the basin, stone quarries are operated in younger, thinner rock strata of Pennsylvanian age. These strata also overlie the thick limestones and dolomites quarried along the margins of the state. The quarries located within the basin area produce stone for agricultural limestone, roads, and other purposes.

HOW AND WHERE ARE LIMESTONE AND DOLOMITE USED?

Millions of tons of stone are crushed annually to produce aggregate for use in making concrete roads and buildings, for road surfacing, and for agricultural limestone. Agstone is applied to farmlands to neutralize soil acidity, improve soil structure, add calcium and magnesium, and promote conditions favorable for the utilization of soil materials by plants. Large quantities of limestone are used in making lime and cement. There are three cement plants in northern Illinois—two at LaSalle and one at Dixon—and one in southern Illinois, at Joppa.

Small amounts of stone are used for making alkalies and glass, for railroad ballast, for building stone, for dusting coal mines to prevent coal dust explosions, and for ingredients in mineral feeds for livestock.

HOW MUCH STONE DOES ILLINOIS PRODUCE?

A production of about 36 million tons of stone in 1963 was valued at almost $48,000,000. The cement made from Illinois limestone in the same year was valued at $32,000,000.

CLAY

WHAT IS CLAY AND HOW IS IT FORMED?

Weathering or alteration of some rocks produces clay which is a very fine-grained, unconsolidated rock. Clay is made up of a group of minerals, of which illite, montmorillonite, kaolinite, and chlorite are the most abundant.