Word Study
phenocryst
CIDE DICTIONARY
phenocryst, n. [Gr. to appear + crystal.].
One of the prominent embedded crystals of a porphyry. [Webster 1913 Suppl.]
OXFORD DICTIONARY
phenocryst, n. a large or conspicuous crystal in porphyritic rock.
Etymology
F ph{eacute}nocryste (as PHENO-, CRYSTAL)
For further exploring for "phenocryst" in Webster Dictionary Online