Source : Webster's Revised Unabridged Dictionary (1913)

Porphyry \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.