Bentonite: Bentonite is a natural clay, with the mineral montmorillonite as an important constituent - getting its name from Montmorillon, France where montmorillonite was discovered in 1847. From this constituent bentonite derives its specific properties, such as its capacities for suspending, supporting, stabilising and swelling. The clay originates from the deposit of volcanic ash-rain on salty inland lakes.

Through shifting of the earths crust these sediments rose above the level of the water, and under the influence of weather and time, bentonite came into being. The remarkable features of this clay were first discovered, in modern times, in the State of Wyoming (U.S.A.) at Fort "Benton" (to which bentonite owes its name).

Two kinds of bentonite can be distinquished; the natural sodium bentonite, called Wyoming bentonite and the bentonite of a calcium nature, which is transformed by a process of activation into an "activated" sodum-bentonite.

Deposits: Bentonite is excavated from open-cast mines; the Wyoming bentonite comes from the State of Wyoming and surrounding regions. The calcium bentonite is found throughout the world. In Europe the most important mines are in Southern Germany and the Mediterranean area.
 

Mineralogical Synthesis:  The quality of bentonite is determined by the content of montmorillonite. A good bentonite contains 80-90 % montmorillonite; the rest is mainly quartz and illite.
 

Applications: In the oil and gas drilling industry, bentonite is an important constituent in the drilling fluid (mud) as it gives the "mud" the necessary stability, viscosity, supporting and swelling capacity. These characteristics of the bentonite have also led to its use in civil engineering for landfill lining and capping, diaphragm (slurry) walls and drill piles.