Early Americans found bentonite vital to their lives. Pioneers found moistened bentonite to be an perfect lubricant for squeaky wagon wheels. The mixture was also used as a sealant for log cabin roofing. The Indians found bentonite useful as a soap.
Small amounts of Wyoming bentonite were first commercially mined and developed in the Rock River area during the 1880s. Newer, more considerable deposits were discovered in other parts of Wyoming during the 1920s and the first processing plant in Wyoming was built during this period. Since that time many other processing plants have been built for the purpose of processing Wyoming sodium bentonite. Wyoming's Bentonite industry produced over 4.0 million tons of bentonite in 1999, with 644 mine and mill employees, and 240 contractor employees.
Exploration for new bentonite beds is normally gifted with auger bit drilling. Once the auger drill stem reaches the soft bentonite it sinks very fast, which indicates to the driller that bentonite has been found. The auger flights are then withdrawn and the "sticky" bentonite is sampled from the flights for quality analysis. Bentonite is mined by surface "open pit" methods. Various types of heavy equipment including bull dozers and rubber-tired scrapers are used to remove the shale rock overlying the bentonite.
Topsoil, as well as the underlying material, is cautiously removed and stockpiled. These "overburden" materials as they are called will be placed back and reseeded once the bentonite has been removed. The bentonite which is bare during this process can be as little as 1 1/2 feet or as much as 10 feet thick. This is the material which is mined and processed.
Many bentonite manufactures prefer to "field dry" the exposed bentonite prior to hauling it to the processing plants. This is accomplished by plowing and discing while taking advantage of the low humidity and sunny days to dry the bentonite prior to its removal. The moisture level prior to "field drying" can exceed 30%. This process will usually extract 15 to 20% of the moisture from the clay prior to hauling.