phenocryst

[ fee-nuh-krist, fen-uh- ]

nounPetrology.
  1. any of the conspicuous crystals in a porphyritic rock.

Origin of phenocryst

1
First recorded in 1890–95; pheno- + cryst(al)

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

How to use phenocryst in a sentence

  • In a basal flow in Moraine Park, the slaggy and compact phases show differences in phenocrysts as well as in groundmass.

    Mount Rainier | Various
  • In Moraine Park gray andesites also predominate, with both pyroxenes as phenocrysts, but here hypersthene is the more important.

    Mount Rainier | Various
  • The camptonites (called after Campton, New Hampshire) are dark brown, nearly black rocks often with large hornblende phenocrysts.

  • Of the darker phenocrysts, the pyroxenes are more abundant than the olivine or hornblende.

    Mount Rainier | Various
  • Many dolerites are porphyritic and carry phenocrysts of olivine, augite and plagioclase felspar (or of one or more of these).

British Dictionary definitions for phenocryst

phenocryst

/ (ˈfiːnəˌkrɪst, ˈfɛn-) /


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

Origin of phenocryst

1
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

Scientific definitions for phenocryst

phenocryst

[ nə-krĭst′ ]


  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.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.