Porphyry

n.

1.

(Geol.) A term used somewhat loosely to designate a rock consisting of a fine-grained base (usually feldspathic) through which crystals, as of feldspar or quartz, are disseminated. There are red, purple, and green varieties, which are highly esteemed as marbles. Porphyry shell (Zool.) a handsome marine gastropod shell (Oliva porphyria), having a dark red or brown polished surface, marked with light spots, like porphyry.

Noun

1.

porphyry - any igneous rock with crystals embedded in a finer groundmass of minerals Synonyms: porphyritic rock

groundmass, igneous rock, porphyritic rock