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[fee-nuh-krist, fen-uh-] /ˈfi nə krɪst, ˈfɛn ə-/
noun, Petrology
any of the conspicuous crystals in a porphyritic rock.
1890-95; pheno- + cryst(al) Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for phenocryst
  • phenocryst poor, with common olivine and rare plagioclase.
  • The pumice component includes coarsely vesiculated, phenocryst-rich and finely vesiculated, phenocryst-poor types.
  • Features such as phenocryst abundance or remanent magnetization provided additional criteria for distinguishing volcanic units.
  • It is an essential phenocryst in some varieties of lamprophyre.
British Dictionary definitions for phenocryst


/ˈfiːnəˌkrɪst; ˈfɛn-/
any of several large crystals that are embedded in a mass of smaller crystals in igneous rocks such as porphyry
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
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phenocryst in Science
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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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