Clay Mineralogy Program

The ISGS Clay Mineralogy Program supports service and research in a variety of areas including: industrial minerals, construction, environmental site characterization and remediation, coal, petroleum, groundwater, and archeology. The clay mineralogy program

  • inventories clay and shale resources as part of the state's geological mapping program
  • provides service to Illinois clay producers and the public using the latest geological research and historical information
  •  characterizes and maps the availability and distribution of clay and shale resources suitable for manufacture of brick and other ceramic based products
  • maintains a database of existing and abandoned clay pits
  •  provides mineralogical and geochemical information
  • assists producers in better utilization of existing resources and locating new sources
  • maintains a repository of data for characterization of Illinois clay and shale resources for present and future exploration.

Clay and Shale

Scott Koenig operates an X-ray diffraction machine The primary clay minerals important to the industrial development of Illinois include illite, kaolinite, chlorite, vermiculite, and montmorillonite. Clay materials are either used directly, as in Native American-carved claystone artifacts, pet litter, engineering fill, and impermeable barriers to water and waste migration, or they are fired into ceramic products and into flux for cement manufacture. Clay and shale are used to manufacture bricks, ceramic tiles, and light-weight aggregate, an essential element for large building structures. Clay and shale are also important ingredients in the production of portland cement, a key binding agent used in concrete.

The mica-like clay mineral illite was named for the state of Illinois. In Illinois it is the most abundant clay mineral in surficial and bedrock strata and in the shales used for ceramics. Absorbent clays or fuller's earth, such as the Porters Creek Clay of southern Illinois, absorbs both oil- or water-based liquids. This property makes these clays ideal for use as oil absorbent sweep-up compounds and as pet litter. Absorbent clays are also expandable, making them excellent thickeners and valuable for applications where low permeability is needed, such as in waste barriers and landfill liners.


Native Americans in Illinois once used upland soils and river-bottom sediments for ceramics, creating both ceremonial and utilitarian items. European settlers used a similarly wide range of materials to create pottery, paving and building bricks, field drain tiles, and structural blocks and tile for buildings. Ceramic field drain tiles were an early innovation that made possible cultivation of much of Illinois' seasonally wet soils.

Although brick and tile manufacturing was once an important part of Illinois' indust rial mineral economy, competition from other markets has diminished its importance in today's state economy. The number of ceramic plants in Illinois dropped from over 100 at the start of the twentieth century to three at the end of the century.