Rock & Mineral Encyclopedia

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

Cat's Eye Tourmaline

Tourmaline displaying chatoyancy, a moving band of light caused by parallel tube-like inclusions, when cut as a cabochon.

A black volcanic glass threaded with delicate grey, swirling lace-like bands of flow lines that show beautifully when polished.

Beryl displaying chatoyancy, a bright moving band of light, caused by parallel tube-like inclusions when cut as a cabochon.

A vivid green chromium-bearing diopside, an affordable emerald-like gem mined largely in Siberia.

A precious opal showing dominant peacock-like blue, green and teal play-of-color, often on Ethiopian material.

A sought-after elbaite tourmaline in teal hues that blend blue and green, prized for its ocean-like color.

An intensely green tourmaline colored by chromium and vanadium, prized for its vivid emerald-like color from East Africa.

An opal cut to show chatoyancy, a sharp moving band of light like a cat's eye, usually in honey, green or yellow common opal.