(redirected from Phenocrysts)
Also found in: Encyclopedia.


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 ?
Disseminated magnetite-chalcopyrite is present within the matrix, largely as a replacement of mafic phenocrysts. Miarolitic cavities locally comprise up to 20% of the rock, and in places, contain the same hydrothermal mineral assemblage as the stockwork veins, including quartz, magnetite, chalcopyrite and trace bornite.
The mineralisation is hosted by a large flow banded rhyolite flow or sill with large phenocrysts of quartz and feldspar throughout the unit.
The Phenocrysts in the granite is feldspar and quartz however, the groundmass consists of Perthtized alkali feldspar, quartz, muscovite and biotite.
The porphyritic dacite is of light green colour having 5% phenocrysts within a fine feldspar matrix.
Textural and chemical variation in plagioclase phenocrysts from the 1980 eruptions of Mount St.
The West Scotch Settlement porphyry has abundant euhedral to anhedral feldspar and quartz phenocrysts in an aphantic matrix.
Ince, "Influence of orthoclase phenocrysts on point load strength of granitic rocks," Engineering Geology, vol.
In situ Sr-isotope ratios were determined on plagioclase phenocrysts (Figures 7(c)-7(e)), from both domes and enclaves, which preserve evidence of the complex history of interaction between the mafic (i.e., enclaves) and felsic (i.e., rhyodacitic domes) magmas in their growing zones [8].
The phenocrysts include orthopyroxene, clinopyroxene, plagioclase, and Timagnetite.
With the continuous crystallization of olivine phenocrysts, the heavy Fe isotope enrichment in basalts increases [10].