The United States is fortunate to have several world class clay deposits within its
boundaries. Each of these deposits will be discussed, which will include location, geology,
mineralogy and principal applications. The clay deposits that are included are
kaolins; ball clays; bentonites, including sodium montmorillonite; calcium montmorillonite;
hectorite, a lithium montmorillonite and palygorskite and sepiolite.
The largest good quality deposits of kaolin in the world are located in Georgia
and South Carolina. Over 500,000,000 tons of kaolin has been shipped since about
1900, when the first processing plants were installed. Currently, the annual tonnage
shipped is about 8,000,000 tons, of which approximately 35 percent is exported.
The sodium bentonite deposits located in South Dakota, Wyoming, and Montana
are the highest quality and largest deposits of this type in the world. These bentonite
beds are altered Cretaceous volcanic ash. Calcium bentonite deposits are located in
several areas of the U.S., including Arizona, Texas, Mississippi, Alabama, Georgia,
Tennessee, Illinois and Missouri. These bentonites range in age from Cretaceous to
Paleocene. Hectorite, a lithium montmorillonite, is present in California and Nevada,
and is hydrothermal in origin.
Palygorskite (attapulgite) deposits are located in southern Georgia and northern
Florida. The terms palygorskite and attapulgite are synonymous. These deposits are
world class and annual shipments are nearly 2,000,000 tons. These minerals form
elongate crystals and have several applications that are primarly due to the elongate
shape. The only sepiolite occurrence is in the Amargosa Valley in southern Nevada.
All of these clays are important industrial minerals and have extensive applications,
which will be discussed.