A hard igneous rock, originally recognized as the Egyptian variety now known as "Imperial" porphyry containing crystals of feldspar in a purplish groundmass. It was prized in the sculpture and architecture of the ancient Romans as well as by later civilizations. Also considered porphyry are rocks of other colors including a green variety from Greece which dotted with green bits of feldspar.(pr. POR-fə-ree)Also see stone.