Tridymite

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Related to Trydimite: cristobalite

tridymite

[′trid·ə‚mīt]
(mineralogy)
SiO2 A white or colorless crystal occurring in minute, thin, tabular crystals or scales; a high-temperature polymorph of quartz.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Tridymite

 

a mineral that is one of the crystalline polymorphs of SiO2. Such trace elements as Fe, Al, and Na are commonly found in tridymite. It crystallizes in the form of colorless or gray tabular crystals, spherical aggregates, spear-shaped twins, and, often, trillings. It is a rare mineral and is usually encountered in cavities of juvenile extrusive acidic rocks and in tuffs; it is also found in meteorites and moon rocks. As a constituent of Dinas brick, tridymite determines the refractory properties of the brick.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.