Figure 3—An Illinois dolomite quarry.
Cement.—Portland cement, sometimes called simply cement, is made at LaSalle, Oglesby, and Dixon in northern Illinois from limestone and a smaller, carefully measured amount of clay or shale. Cement also is made at Joppa in southern Illinois. The blend of materials is thoroughly ground and mixed, then heated at a high temperature in huge rotating horizontal furnaces, called kilns, until it forms a clinker. After it cools, the clinker is ground to a flourlike powder. This is basically the cement that binds together the mixture of sand and limestone (or dolomite), or of sand and gravel, to make the concrete from which roads, bridges, buildings, and other structures are made.
Aggregate.—The crushed stone used in making concrete is known as concrete aggregate. This is a major use for Illinois limestones and dolomites. Large amounts of stone aggregate also are used in bituminous roads, popularly called “blacktop” roads.
Agricultural Uses.—Agricultural limestone (agstone) is applied to farm land to neutralize soil acids and otherwise benefit the soil. Both limestone and dolomite are so used. Chickens are fed small limestone chips to provide calcium for the formation of egg shells. Pigs and cows get calcium from mineral supplements containing powdered pure limestone.
Figure 4—An underground limestone mine.
Other Uses.—Illinois limestone or dolomite is used in steel making, as building stone and marble, as road stone, as ballast for the road beds of railroad tracks, for making refractory dolomite used in the steel industry, and for a variety of less common uses.
Quarries
There are about 200 stone quarries in Illinois. Most of the larger quarries ([fig. 3]) are in the Chicago, Joliet, Kankakee, and East St. Louis areas, but one or more limestone or dolomite quarry occurs in many counties.
If all the stone taken from Illinois quarries in 1963 were removed from a hole 100 feet square, the hole would penetrate into the earth about 8 miles. It would take more than 350,000 railroad cars holding 100 tons each to haul away the stone. Limestone, dolomite, and their products added over 80 million dollars to the economy of the state in 1963, approximately 8 dollars for each person in Illinois.