Bentonite is an absorbent
aluminium phyllosilicate generally impure
clay consisting mostly of
montmorillonite. There are a few types of bentonites and their names depend on the dominant elements, such as potassium, sodium, calcium, and aluminium. As noted in several places in the geologic literature, there are some nomenclatorial problems with the classification of bentonite clays.
Bentonite usually forms from weathering of
volcanic ash, most often in the presence of water. However, the term bentonite, as well as a similar clay called tonstein, have been used for clay beds of uncertain origin. For industrial purposes, two main classes of bentonite exist: sodium bentonite and calcium bentonite.
In
stratigraphy
Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks.
Stratigrap ...
and
tephrochronology, completely devitrified (weathered volcanic glass) ash-fall beds are commonly referred to as K-bentonites when the dominant clay species is
illite. Other common clay species, and sometimes dominant, are montmorillonite and
kaolinite
Kaolinite ( ) is a clay mineral, with the chemical composition Al2 Si2 O5( OH)4. It is an important industrial mineral. It is a layered silicate mineral, with one tetrahedral sheet of silica () linked through oxygen atoms to one octahedral ...
. Kaolinite dominated clays are commonly referred to as tonsteins and are typically associated with
coal.
List of producing countries
This is a list of countries by
bentonite production (tonnes) in 2006 mostly based o
British Geological Surveyaccessed in June 2008.
* indicates "Natural resources of COUNTRY or TERRITORY" links.
References
External links
{{DEFAULTSORT:Bentonite production
*
Lists of countries by mineral production