No salt is now produced in Illinois, but at one time the state was a major salt producer. Salt works were in operation near Equality, Central City, Murphysboro, St. John, Danville, and possibly other places. The salt was obtained by evaporating salt water (brine) that came from natural springs or from wells. The Equality area was a particularly important producer of salt in the 1800’s. Discovery elsewhere in the Middle West of deposits of rock salt and brines that contained more salt than those of Illinois is said to have been responsible for the discontinuance of salt making in the state.
No salt beds crop out in Illinois, nor are any known to have been encountered in the many wells that have been drilled for coal, oil, or water. However, most oil well drilling encounters brines containing various amounts and kinds of salts, including the common table salt, sodium chloride.
For reasons relating to the production of oil, Survey geologists and chemists have collected and analyzed many samples of Illinois oil field brines, and data are therefore available on their salt content. No commercial use is being made of the brines as sources of salt.
Oil Shale
Illinois has a large oil-producing industry that obtains oil from wells. The state also contains beds of shale that yield oil when the shale is heated.
In order to estimate the present and future importance of the oil shale resources, the Survey collected and tested more than 100 shale samples from 41 Illinois counties. A few samples contained more than 25 gallons of oil per ton of shale, but most contained less than 15 gallons per ton. A study of the crude oil distilled from selected shale samples showed it to be somewhat different from the oil that comes from wells. It could, nevertheless, be made to yield gasoline, fuel oil, and other products if suitably processed.
The shale strata generally the richest in oil are found above coal seams, are black, and are sometimes called slate by coal miners. They are rarely more than 3 feet thick, but they extend over large areas.
Sandstone
Sandstone has a long history of use in Illinois. Pioneers built foundations for their houses and barns and curbs around their wells from it. Slabs of sandstone were once a popular material for sidewalks, some of which are still in use. Churches and other sizable buildings have been constructed from it, and at one time an Illinois sandstone was used to make grindstones. Except for the St. Peter Sandstone, which was discussed under “Silica Sand,” the use of sandstone has decreased, although comparatively small quantities are still used as building stone.
Most Illinois sandstones may be thought of as a mass of sand whose grains are more or less firmly cemented together by clay, iron oxide, and quartz, either singly or in combination, or, less commonly, by calcite. The grains are particles of various minerals, but most of them are quartz.