\Por"phy*ry\, n.; pl. {Porphyries}. [F. porphyre, L.
porphyrites, fr. Gr. ? like purple, fr. ? purple. See
{Purple}.] (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} (Zo["o]l.), a handsome marine gastropod
   shell ({Oliva porphyria}), having a dark red or brown
   polished surface, marked with light spots, like porphyry.