What we mine in LaSalle County
Industrial minerals
Industrial minerals have played a critical role in the development of Illinois since the beginning of pioneer settlement in the eighteenth century. Illinois industrial minerals include rocks such as limestone, dolomite, and shale and nonmetallic minerals such as silica sand, clay, and fluorite. Major industrial minerals produced in Illinois today are crushed stone (limestone and dolomite), sand and gravel, clay, silica sand, tripoli (microcrystalline quartz), and peat. Portland cement, lime, and brick are also manufactured. Portland cement is produced from low-magnesium limestone, lime from limestone and dolomite, and brick from clay and shale. Production and use of industrial minerals have been and will continue to be a key component of the state's economy.
Limestone
Limestone and dolomite are the most widely quarried rocks in Illinois, and crushed stone is the state's most important rock product. Millions of tons of stone are crushed annually for use as construction aggregates, road surfacing material, agricultural limestone, and lime. High calcium limestones are also used as a scrubbing agent for pollution control in power plants and incinerators and as a major ingredient of cement, the binding agent used in concrete pavements and foundations. Limestone and dolomite quarries are located where thick stone deposits occur near the surface, mainly in the northern quarter of the state, the western side of the state, and near the state's southern tip. These deposits are also mined underground in some areas. Underground mining is becoming a desirable method for extracting crushed stone, especially in populated areas and where stone is deeply buried.
Sand and gravel
Sand and gravel deposits are widely distributed in select locations across the state; they are most abundant and of highest quality in northeastern Illinois, but less abundant and lower quality elsewhere. Sand and gravel is formed by erosion and in much of Illinois was deposited by water from the melting glaciers. The huge ice lobes of continental ice sheets that moved into Illinois from Canada carried enormous amounts of rock debris, much of which was washed and sorted by meltwaters into various sand and gravel deposits. Sand deposits of more recent origin are found in larger streams and rivers, where they are recovered by dredging. Many deposits of sand and gravel are used as construction aggregate in asphalt and in concrete pavements and commercial and residential structures, especially in the northern half of the state.
Silica sand
Silica sand consists of fine grains of the mineral quartz. Commercial silica sand is produced from sandstone bedrock and some glacial deposits. Silica sand from northern Illinois is famous for its high purity and is widely used in making high-quality glass. Silica sand is also used as molding sand because it can withstand the high temperatures used in casting steel and other metals. It is also used in fracture-treating wells to help increase oil and gas production. In ground or fine powder, silica sand is used as an ingredient in paint fillers, pottery glazes, and enamel.
Excerpted from Illinois State Geological Survey's Illinois' Industrial Minerals webpage (accessed 7/21/14).
More about silica sand
Learn more about frac sand mining and how it is used in modern oil and gas extraction by reading the article titled Estimates of Hydraulic Fracturing (Frac) Sand Production, Consumption, and Reserves in the United States by Don Bleiwas, Physical Scientist, U.S. Geological Survey (accessed 7/30/15).
Sand mines are a necessary component in the hydraulic fracturing (i.e., fracking) process. Learn more about the economic benefits of sand mining in this YouTube video Fracking Facts: Benefits of Frac Sand Mining produced by The Heartland Institute.