[ fee-nuh-krist, fen-uh- ]
/ ˈfi nə krɪst, ˈfɛn ə- /

noun Petrology.

any of the conspicuous crystals in a porphyritic rock.

Origin of phenocryst

First recorded in 1890–95; pheno- + cryst(al) Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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 for phenocryst

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

Science definitions for phenocryst


[ fēnə-krĭst′ ]

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.