Rock & Mineral Encyclopedia

Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.

Anorthite

The calcium end-member of the plagioclase feldspar series, a high-temperature mineral common in mafic rocks, meteorites and lunar samples.

A general field term for green, low-grade metamorphosed basaltic rocks colored by chlorite, epidote, and actinolite.

A general term for light-colored, fine-grained volcanic rocks rich in quartz and feldspar, like rhyolite.