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Early Americans found bentonite vital to their lives. Pioneers found moistened bentonite to be an ideal 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 substantial 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.

Wyoming bentonite is composed essentially of montmorillonite clay, also known as hydrous silicate of alumina. In more simplistic terms, the structure of bentonite is much like a sandwiched deck of cards. When placed in water, these cards or clay platelets shift apart. Bentonite attracts water to its negative face and magnetically holds the water in place. because of this unique characteristic, Wyoming bentonite is capable of absorbing 7 to 10 times its own weight in water, and swelling up to 18 times its dry volume.

Exploration for new bentonite beds is normally accomplished with auger bit drilling. Once the auger drill stem reaches the soft bentonite it sinks very rapidly, 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 The auger flights are then withdrawn and the "sticky" bentonite is sampled from the flights for quality analysis.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 carefully 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 exposed 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 normally extract 15 to 20% of the moisture from the clay prior to hauling.

Upon arrival at the processing plants, the bentonite is placed into designated stockpiles and carried into the plant with front-end loaders. The bentonite is then dried in a long cylinder called a rotary dryer where approximately 10 to 15% of the moisture is removed. Natural gas or coal are used primarily as fuels for drying. The finished product has moisture content of 7 to 10%.

Once delivered from the rotary dryer, the bentonite is processed into either a fine powder or granulated into a small particle or flake. Packaging of the product is the last process to be undertaken. Granular bentonite is a major constituent of "scoopable" cat litter. Bentonite can be packaged in 50 lb., 100 lb. or up to 4,000 lb. super sacks. After the packaging process takes place, the bentonite is shipped either by truck or rail to the consumer. Another form of packaging is to ship direct in bulk pneumatic trucks or rail cars to the consumer.

Drilling mud, or drilling gel, is a major component in the well drilling process. Drilling mud is crucial in the extraction of drill cuttings during the drilling process. Bentonite, when mixed with water, forms a fluid (or slurry) that is pumped through the drill stem, and out through the drill bit. The bentonite extracts the drill cuttings from around the bit, which are then floated to the surface. The drilling mud, or gel, also serves to cool and lubricate the drill bit as well as seal the drill hole against seepage and to prevent wall cave-ins

Taconite, a low grade iron ore, has been developed as an economic source for iron. During processing, the taconite is ground into a very fine powder. The ground taconite is then mixed with small amounts of bentonite which serves as a binder to the taconite. This mixture is processed into balls or pellets. The process is finished when these pellets are sintered in rotary kilns that give the pellets a hard surface. The taconite pellets are easy to handle at this point and can be loaded into various containers for shipment to steel mills.

Bentonite serves as an economical bonding material in the molding processes associated with the metal casting industry. Bentonite, when mixed with foundry molding sands, forms a pliable bond with the sand granules. Impressions are formed into the face of the bentonite/sand mixtures. Molten metal is pored into the impressions at temperatures exceeding 2,800 F. The unique bonding characteristics of bentonite insures the durability of the mold during these high temperatures. Once the process is complete, the bentonite/sand mold can then be broken away from the casting face and reused.

In recent years, bentonite has become a major component in the manufacturing of cat litter. Because of the unique water absorption, swelling, and odor controlling characteristics of bentonite, it is ideal for use in "clumping" types of cat litters. Clumping cat litter has become widely accepted as an economical alternative to conventional non-clumping type cat litters. Because bentonite forms clumps when wet, the clumps can easily be removed and disposed of. The remainder of the unused material stays intact and can continue to be used. clumping cat box litters will last longer with less frequency of changing.

For many years bentonite has been used as a binder in the feed pelletizing industry. Small amounts of bentonite can be added to feed products to insure tougher, more durable pellets. By absorbing excess moisture and oils, bentonite aids in the free movement of pellets, preventing lumping and caking. Research has been conducted which indicates that bentonite has additional benefits for both animals and poultry. The bentonite used in the feed slows the digestive system and enables the animal or fowl to better utilize the feed nutrients. Other studies have shown bentonite as a useful ingredient in the control of certain toxins which affect animals and fowl.

Bentonite has also proved helpful in sealing freshwater ponds, irrigation ditches, reservoirs, sewage and industrial water lagoons, and in grouting permeable ground. In addition, it has been used in detergents, fungicides, sprays, cleansers, polishes, ceramic, paper, cosmetics and applications where its unique bonding, suspending or gellant properties are required.

Last Update 07/20/05

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