• synonyms


[fee-nuh-krist, fen-uh-]
noun Petrology.
  1. any of the conspicuous crystals in a porphyritic rock.
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Origin of phenocryst

First recorded in 1890–95; pheno- + cryst(al)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for phenocryst


  1. any of several large crystals that are embedded in a mass of smaller crystals in igneous rocks such as porphyry
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Word Origin

C19: from pheno- (shining) + crystal
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

phenocryst in Science


  1. A large crystal that is surrounded by a finer-grained matrix in an igneous rock. Phenocrysts are usually the first crystals to form from a cooling magma, and therefore have sufficient room to grow to a large size. They are analogous to porphyroblasts in metamorphic rock.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.