• synonyms


noun Mineralogy.
  1. a white or gray feldspar mineral, CaAl2Si2O8, calcic plagioclase.
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Origin of anorthite

First recorded in 1825–35; an-1 + orth- + -ite1
Related formsan·or·thit·ic [an-awr-thit-ik] /ˌæn ɔrˈθɪt ɪk/, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for anorthite

Historical Examples

  • Anorthite occurs in white translucent or transparent crystals.


    James Geikie

  • Anorthite is an essential constituent of many basic igneous rocks, such as gabbro and basalt, also of some meteoric stones.

  • Rougemonite consists largely of anorthite with pyroxene as the only important ferro-magnesian constituent.

  • Like labradorite and anorthite, it is a common constituent of basic igneous rocks, such as gabbro and basalt.

British Dictionary definitions for anorthite


  1. a white to greyish-white or reddish-white mineral of the feldspar group and plagioclase series, found chiefly in igneous rocks and more rarely in metamorphic rocks. It is used in the manufacture of glass and ceramics. Composition: calcium aluminium silicate. Formula: CaAl 2 Si 2 O 8 . Crystal structure: triclinic
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Derived Formsanorthitic (ˌænɔːˈθɪtɪk), adjective

Word Origin

C19: from an- + ortho- + -ite 1
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

anorthite in Science


  1. A white to gray triclinic mineral of the plagioclase feldspar group. Anorthite is the plagioclase mineral that is richest in calcium and occurs in alkaline igneous rocks such as gabbro. Chemical formula: CaAl2Si2O8.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.