Figure 11—The clay industry is scattered widely in Illinois. Many manufacturing plants are located at the clay pits.
KEY Pit or Plant
Almost every county has some sand and gravel, but the major areas of production are northeastern Illinois and some of the major rivers. Considerable tonnages of sand and gravel are dredged from bars in the channels of the Mississippi, Ohio, and Wabash Rivers.
Silica Sand
Silica sand is used in making glass, for sand blasting, as grinding sand, as molding sand for casting steel, and in the fracture treatment of oil wells to increase oil production. Some of the sand is finely pulverized into a powder that is used as a filler, a fine abrasive, as a ceramic material, and for many other purposes.
This special sand, composed of grains of the mineral quartz (silica), comes from a sandstone of Ordovician age that is mined in LaSalle and Ogle Counties.
Tripoli and Ganister
Tripoli, or “amorphous” silica, is mined from Devonian rocks in Alexander County. The silica is finely ground for use as a polishing agent, as a filler, in buffing compounds, and for other purposes.
Ganister, a granular material with a high silica content, also is mined in extreme southern Illinois. It is used in making products that can withstand high temperatures.