Rock & Mineral Encyclopedia

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

Purple Opal

A purple-hued common opal, much of it the Mexican "morado" type, valued for even violet color rather than play-of-color.

A trade name for quartz containing a combination of seven minerals including amethyst, smoky quartz, and cacoxenite, prized by collectors.

A treated chalcedony with a network of crackled veins, usually heated and dyed in vivid colors for affordable, eye-catching beads.

A deep black variety of banded chalcedony, often closely related to or treated like onyx, used for jewelry and carvings.

A copper-iron sulfide ore famous for its iridescent peacock-like purple and blue tarnish; often sold as treated chalcopyrite.

Tabular quartz crossed by a milky white thread-like line marking where the crystal repeatedly cracked and re-healed.