Origin: F. Porphyre, L. Porphyrites, fr. Gr. Like purple, fr. Purple. See Purple.
(Science: geology) 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.