Michael Smith

Porphyritic rhyolite has large, well-formed crystals, mostly alkali feldspar, plagioclase, quartz, and less often hornblende, pyroxene, or mica in a

Porphyritic basalt rocks have large, well-formed grains of calcic plagioclase, augite, olivine, and sometimes hornblende in fine-grained dark-gray to black

Porphyritic granite has large, well-formed white or pink alkali feldspar and sometimes quartz, biotite, or plagioclase in a finer but

Porphyritic gabbro has large, well-formed crystals of mostly calcic-plagioclase and sometimes augite, rarely olivine or other mafic minerals set in

Porphyritic diorite rocks have large, well-formed mineral grains of feldspar and sometimes hornblende, pyroxene, or biotite set in a finer-grained

Porphyritic trachyte rocks have large, well-formed sanidine, plagioclase, and sometimes amphibole, biotite, or pyroxene crystals in a fine-grained matrix. The

Porphyritic phonolite or phonolite porphyry has well-formed, large leucite, nepheline, and alkali feldspar crystals in a fine-grained matrix. The larger

Purple, red, or Roman Imperial porphyry refers to reddish to purplish porphyritic rocks highly-priced during the antiquity age by Romans