Rock & Mineral Encyclopedia

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

Onyx

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

A pale green variety of feldspar moonstone showing a soft white or bluish adularescent sheen over a greenish body.

A hydrated silica gemstone famous for its shimmering play-of-color, ranging from white and black opal to fiery orange fire opal.

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