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

montmorillonitic [mont-muh-ril-uh-nit-ik] , adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
montmorillonite (ˌmɒntməˈrɪləˌnaɪt)
a clay mineral consisting of hydrated aluminium silicate: an important component of bentonite
[C19: named after Montmorillon, French town where it was first found, + -ite1]

Collins English Dictionary - Complete & Unabridged 10th Edition
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Encyclopedia Britannica


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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Example sentences
Bentonite is an absorbent aluminum phyllosilicate generally impure clay consisting mostly of montmorillonite.
The typical clay of choice for these composites is montmorillonite.
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