[ben-tn-ahyt] 
| a clay formed by the decomposition of volcanic ash, having the ability to absorb large quantities of water and to expand to several times its normal volume. |
[ben-tn-it-ik] , adjective | ben·ton·ite (běn'tə-nīt') n. An absorbent aluminum silicate clay formed from volcanic ash and used in various adhesives, cements, and ceramic fillers. [After Benton Formation (formerly Fort Benton Formation) of the Rock Creek district in eastern Wyoming.] ben'ton·it'ic (-nĭt'ĭk) adj. |
bentonite
clay formed by the alteration of minute glass particles derived from volcanic ash. It was named for Fort Benton, Mont., near which it was discovered
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tnˌaɪt