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.

A brownish-red to deep brown variety of chalcedony, closely related to carnelian but darker, colored by iron oxides.

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