WHAT IS THE BENTONITE?

BENTONITE DEFINITION

Bentonite is an absorbent aluminum phyllosilicate consisting mainly of montmorillonite, which is not mostly pure clay. The name bentonite was given to absorbent clay by Wilbur C Knight after the Cretaceous Benton Shale near Rock River, Wyoming.
There are three different types of bentonite, named after its respective dominant element, such as potassium (K), sodium (Na), calcium (Ca) and aluminum (Al). Experts argue over the naming problems related to the classification of bentonite clays.
Bentonite is generally formed by weathering of volcanic ash, mostly in the presence of water. However, the term bentonite is used to describe clay deposits of uncertain origin, as in a similar clay called tonstein.
There are two basic classes of bentonite for industrial purposes: sodium and calcium bentonite. In stratigraphy and tetrachronology, ashfall deposits that are fully vitrified (eroded volcanic glass) are commonly referred to as K-bentonite when the dominant clay type is ilite.
Other common clay types, and sometimes the dominant ones, are montmorillonite and kaolinite. Clays dominated by kaolinite are commonly referred to as tonstein and are typically associated with coal.