Category:Porphyry

Por"phy*ry, n.; pl. Porphyries. Etym: [f. porphyre, l. porphyrites, Fr. Gr. Purple.] (geol.)

Defn: 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 (zoöl.), a handsome marine gastropod shell (oliva porphyria), having a dark red or brown polished surface, marked with light spots, like porphyry.