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

phe′no·crys′tic adj.


(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]


(ˈfi nə krɪst, ˈfɛn ə-)

any of the conspicuous crystals in a porphyritic rock.
[1890–95; pheno- + cryst (al)]
References in periodicals archive ?
Locally, as near Jam Khan Jo Wandio, it is porphyritic with feldspar phenocryst up to a centimeter in length.
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.
3] in Unit E and its progressive drop from Unit A, through B and C can be explained by the difference in plagioclase phenocryst content in the various units (Table 2).
At Santa Rosa, intrusive dacite, intensely argillically altered in the mine area, contains abundant phenocryst of plagioclase, quartz, hornblende, and biotite.
The phenocryst population can be identified as crystals inherited from one of the parental magmas, but fine grains were inherited from one of the parent magmas or must have formed after the mixing event.
The amphiboles within the intrusion can be texturally divided into phenocryst, matrix, and poikilocrystal amphiboles, and plagioclase within the intrusion is divided into phenocryst and matrix groups.
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.
The phenocryst assemblage is plagioclase augite --hypersthene, these minerals are usually present in glomerocryst assemblages as: 1.
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.
015 Mineral sphene plagioclase plagioclase matrix phenocryst Analysis 637/3 No-8049/2 637/5 Si[O.
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.