Porphyrite

Part of speech: noun

Definitions

1. A dark, hard volcanic rock containing large crystals of feldspar set within a fine-grained mass of matrix
2. An igneous rock notable for its prominent feldspar phenocrysts embedded in a finely textured background
3. A porphyritic volcanic stone whose conspicuous large crystals stand out against a dense, fine-grained groundmass

Etymology: Romans quarried a dark purple-red stone in the Egyptian desert at a site they called Mons Porphyrites, the Purple Mountain. The name came from the Greek "porphyros", purple, the same root that gave the dye made from sea snails. The stone's colour made it prized for imperial monuments and sculpture. Geologists later applied the name to a different rock, a fine-grained igneous rock with larger feldspar crystals, called phenocrysts, scattered through a darker groundmass. This texture is called porphyritic, and the rock is named for it. The connection to the ancient stone is one of resemblance and name rather than shared composition.

Synonyms: porphyry