Studies of Clay and Shale
In view of the significant relationship between the clay minerals and the utilization of the clays and shales in which they occur, the Illinois Geological Survey has investigated extensively the clay minerals in the clay and shale deposits of Illinois. Many samples were studied by means of powerful microscopes, X-ray, and chemical analysis. Most of the surface clays and shales proved to be composed principally of illite or related minerals. The kaolin clay of extreme southern Illinois contains the mineral kaolinite. The older underclays also contain kaolinite, but many of them also contain smaller amounts of illite.
The Survey also has tested many clays to determine their burning properties and color when fired, and hence their potential uses. The bonding capabilities of other clays have been measured to find out whether they can be used as a bonding material for molding sand. The bloating properties of Illinois clays and shales from many deposits have been studied to determine which are suitable for making lightweight aggregate for the manufacture of concrete.
The object of these studies has been to discover the location, character, and possible uses of the state’s clay and shale resources. Special studies are continuing in several parts of the state. Illinois is well endowed with clays and shales that can be used for a variety of purposes and has resources to fill future as well as present needs.