Also found in: Encyclopedia.


A conspicuous, usually large, crystal embedded in porphyritic igneous rock.

phe′no·crys′tic adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Geological Science) relating to a phenocryst
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
References in periodicals archive ?
The andesite has a maximum thickness of 85 m, and it is a non-vesicular, phenocrystic andesite with veins and vugs.
These are phenocrystic rhyolites (or quartz porphyries) recovered from a drill core on the Undva Peninsula, western Saaremaa, underlain by plagioclase porphyrites (Niin 1976).
Phenocrystic plagioclase forms euhedral to subhedral tabular crystals, ranging from 1 to 12 mm long, with rectangular cross sections and polysynthetic albite twinning.