• synonyms


noun Petrology.
  1. a granular plutonic rock composed largely of labradorite or a more calcic feldspar.
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Origin of anorthosite

1860–65; < French anorthose anorthoclase (an- an-1 + Greek orthós straight) + -ite1
Related formsan·or·tho·sit·ic [an-aw-thuh-sit-ik] /ænˌɔ θəˈsɪt ɪk/, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for anorthosite

Historical Examples of anorthosite

  • In Canada great portions of the eastern portion of the Dominion are formed of gabbros, norite, anorthosite and allied rock types.

    Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 4


British Dictionary definitions for anorthosite


  1. a coarse-grained plutonic igneous rock consisting almost entirely of plagioclase feldspar
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Word Origin for anorthosite

C19: from French anorthose (see 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

anorthosite in Science


  1. An igneous rock consisting almost entirely of plagioclase feldspar, especially the labradorite variety. Anorthosites have been identified among rock samples collected from the Moon.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.