a mineral, aluminum silicate, Al2SiO5, occurring in the form of long, slender, and often fibrous crystals.
- Also called fibrolite.
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How to use sillimanite in a sentence
In mica-gneisses sillimanite, kyanite, andalusite and garnet may occur.
sillimanite usually forms exceedingly minute needles embedded in quartz.
British Dictionary definitions for sillimanite
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
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
Scientific definitions for sillimanite
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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