Porphyry

About it

Any igneous rock with large, well-formed crystals (phenocrysts) set in a much finer groundmass. Imperial porphyry, the purple stone prized by Roman emperors, came from the Eastern Desert of Egypt.

Type

Rock (igneous)

Group

Igneous (porphyritic texture)

Colours

red, purple, green, grey, with paler crystals

Transparency

opaque

Typical values: real specimens vary. For more, see mindat.org.