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[mont-muh-ril-uh-nahyt] /ˌmɒnt məˈrɪl əˌnaɪt/
any of a group of clay minerals characterized by the ability to expand when they absorb large quantities of water.
Also called smectite.
1850-55; named after Montmorillon, France, where it was found; see -ite1
Related forms
[mont-muh-ril-uh-nit-ik] /ˌmɒnt məˌrɪl əˈnɪt ɪk/ (Show IPA),
adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for montmorillonite
  • Bentonite is an absorbent aluminum phyllosilicate generally impure clay consisting mostly of montmorillonite.
  • The typical clay of choice for these composites is montmorillonite.
British Dictionary definitions for montmorillonite


a clay mineral consisting of hydrated aluminium silicate: an important component of bentonite
Word Origin
C19: named after Montmorillon, French town where it was first found, + -ite1
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Encyclopedia Article for montmorillonite

any of a group of clay minerals and their chemical varieties that swell in water and possess high cation-exchange capacities. The theoretical formula for montmorillonite (i.e., without structural substitutions) is (OH)4 Si8 Al4 O20nH2 O.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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