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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.


(ˈfiːnəˌkrɪst; ˈfɛn-)
(Geological Science) any of several large crystals that are embedded in a mass of smaller crystals in igneous rocks such as porphyry
[C19: from pheno- (shining) + crystal]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˈfi nə krɪst, ˈfɛn ə-)

any of the conspicuous crystals in a porphyritic rock.
[1890–95; pheno- + cryst (al)]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
References in periodicals archive ?
Carmichael, "Petrology of Volcan Tequila, Jalisco, Mexico: disequilibrium phenocryst assemblages and evolution of the subvolcanic magma system," Contributions to Mineralogy and Petrology, vol.
Identification of the Deike and Millbrig K-bentonite layers along the Kingston thrust sheet in East Tennessee can be done through the examination of phenocryst mineralogy prominent within each deposit.
Unit A is a moderately to strongly weathered porphyritic basalt with twenty five to thirty five percent large plagioclase phenocrysts. Phenocryst [cores-An.sub.75-86]; [groundmass-An.sub.43-65].
Locally, as near Jam Khan Jo Wandio, it is porphyritic with feldspar phenocryst up to a centimeter in length.
Both matrix and phenocryst plagioclase have similar compositions, with [Na.sub.2]O and CaO concentrations increasing from 7.49 to 8.49 wt% and decreasing from 6.61 to 6.07 wt%, respectively, from core to rim in zoned plagioclase.
2) they are metamorphosed igneous rocks that displays compositional banding where the minerals are arranged into bands of more mafic minerals and more felsic minerals and it occupies a major portion of the study area under the thin section the recrystallized fine grained quartz covers the surface of microcline phenocryst as overgrowths this is a common phenomenon in all the granite gneisses.
That is why the samples of alkali granite with broadly similar mineralogical composition but different phenocryst size have different values of UCS.
This study will produce detailed maps of small but representative areas including: (1) detailed topography to a small contour interval; (2) mapping of lithologic textures including megascopic mineralogy, xenoliths, flow foliations, and phenocryst morphology and distribution; (3) mapping of structures such as joints, fractures, and faults; and (4) surface weathering textures.
Again, within the precision and scatter of the data, there is no significant difference between these average Z values, either among the three different modes of crystallization represented (volcanic phenocryst versus volcanic matrix versus pluton) or between the two ages of plutons represented.
Phenocryst minerals include plagioclase, clinopyroxene, and olivine.