Definition of bentonite in English:



mass noun
  • A kind of absorbent clay formed by breakdown of volcanic ash, used especially as a filler.

    • ‘Sedimentary rocks such as mudstones often contain a variety of clay minerals, including swelling clays such as bentonite.’
    • ‘I work with a low-fire clay body consisting of ball clay, talc and bentonite.’
    • ‘Three types of soils, residual soils, kaolinite and bentonite, were used in the study.’
    • ‘In areas that have a limited clay source, bentonite can be mixed with certain soils and compacted into place, forming a free-swelling water barrier.’
    • ‘Like most clays, bentonite is a hydrated compound of aluminium and silicon oxides, but it differs in ways that are useful to wine-makers.’


Late 19th century: from the name of Fort Benton in Montana, US, where it is found, + -ite.