• synonyms


  1. a granular igneous rock consisting essentially of plagioclase feldspar and hornblende.
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Origin of diorite

1820–30; < French < Greek dior(ízein) to distinguish (see di-3, horizon) + French -ite -ite1
Related formsdi·o·rit·ic [dahy-uh-rit-ik] /ˌdaɪ əˈrɪt ɪk/, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for diorite

Historical Examples

  • Quartz porphyry, diabase and diorite appear in the Ardennes.

    Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 1


  • A diorite block, found at Susa in 1902, has the law engraved on it.

  • Diorite is a crystalline aggregate of a soda-felspar and hornblende.


    James Geikie

  • What is the mineralogical composition of syenite and diorite?


    James Geikie

  • They are in diorite, and have the name of Apepi engraved upon them.

    Ancient Egypt

    George Rawlinson

British Dictionary definitions for diorite


  1. a dark coarse-grained igneous plutonic rock consisting of plagioclase feldspar and ferromagnesian minerals such as hornblende
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Derived Formsdioritic (ˌdaɪəˈrɪtɪk), adjective

Word Origin

C19: from French, from Greek diorizein to distinguish (from dia- apart + horizein to define) + -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

diorite in Science


  1. A gray, coarse-grained plutonic rock. Diorite consists mainly of sodium-rich plagioclase and one or more mafic minerals such as biotite, hornblende, or pyroxene. It is the coarse-grained equivalent of andesite.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.