Rock & Mineral Encyclopedia

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

Amethyst

The purple variety of quartz, colored by iron and natural irradiation, prized as the classic violet birthstone of February.

Purple-colored volcanic glass; genuine natural purple obsidian is rare, with much purple obsidian being manufactured colored glass.

An uncommon purple to violet tourmaline colored by manganese, the deeper reddish-purple stones sometimes called siberite.

The red, chromium-colored variety of corundum, prized as one of the most valuable colored gemstones and second only to diamond in hardness.

A natural bicolor quartz that combines purple amethyst and golden citrine in a single crystal.

A trademarked deep purple-red rhodolite garnet from India, named for its rich grape-like color from the pyrope-almandine series.