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.