• synonyms


  1. a mineral, aluminum silicate, Al2SiO5, occurring in the form of long, slender, and often fibrous crystals.
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Origin of sillimanite

1825–30; named after B. Silliman; see -ite1
Also called fibrolite.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for sillimanite

Historical Examples of sillimanite

  • Sillimanite usually forms exceedingly minute needles embedded in quartz.

    Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 6


British Dictionary definitions for sillimanite


  1. a white, brown, or green fibrous mineral that consists of aluminium silicate in orthorhombic crystalline form and occurs in metamorphic rocks. Formula: Al 2 SiO 5
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Word Origin for sillimanite

C19: named after Benjamin Silliman (1779–1864), US chemist
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

sillimanite in Science


  1. A usually white, pale-green or brown orthorhombic mineral occurring as long, slender, fibrous crystals in metamorphic rocks. It is a polymorph of andalusite and kyanite, but can form at higher temperatures than either of these. Chemical formula: Al2SiO5.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.