Rock & Mineral Encyclopedia

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

Sardonyx

A banded chalcedony combining reddish-brown sard with white or black onyx layers, prized since antiquity for carved cameos.

Clusters of tiny botryoidal chalcedony spheres resembling bunches of grapes, famously purple, found in Indonesia.

A banded variety of chalcedony quartz, classically black or black-and-white, long favored for cameos and beads.

A banded agate whose internal structures resemble cathedral spires, arches, or a city skyline of towers and pinnacles.