labradorite
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labradorite
labradorite (lăbˈrədôrītˌ, lăbrədôrˈīt), a variety of plagioclase feldspar.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.
Labradorite
(named for a deposit on Labrador), a mineral of the soda-lime feldspars—the plagioclases. It is an isomorphic mixture of soda feldspar (albite) with lime feldspar (anorthite). The mineral contains 50–70 percent anorthite. It crystallizes in the triclinic system; it is colorless, white, or gray and forms complex twins, often with an attractive blue-green and golden iridescence. Its hardness is 6 on the Mohs’ scale and its density is 2,680–2,720 kg/m3. Labradorite enters into the composition of many basic magmatic rocks, including gabbros, basalts, and diabases. Rocks consisting almost entirely of labradorite are called labradoritites.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
labradorite
[′lab·rə‚dȯ‚rīt] (mineralogy)
A gray, blue, green, or brown plagioclase feldspar with composition ranging from Ab50 An50 to Ab30 An70, where Ab = NaAlSi3O8 and An = CaAl2Si2O8; in the course of formation when the natural material cools, the feldspar sometimes exhibits a variously colored luster. Also known as Labrador spar.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.