Rock & Mineral Encyclopedia

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

Multicolor Tourmaline

Tourmaline crystals displaying two or more distinct colors at once, including the famous pink-and-green watermelon variety.

A transparent, optical-grade variety of calcite famous for strong double refraction, splitting images and light into two rays.

The titanium-rich black variety of andradite garnet, with a brilliant resinous luster prized for mourning and statement jewelry.

An old name for a dull leek-green variety of quartz or chalcedony colored by green mineral inclusions, historically called mother of emerald.

A warm peach-to-apricot variety of moonstone feldspar showing a soft billowy sheen (adularescence) caused by internal light scattering.

An exceptionally hard beryllium aluminum oxide prized for golden hues, sharp cat's-eye effect, and the rare color-change alexandrite variety.

A pleochroic aluminum silicate that flashes green and reddish-brown from different angles, with a cross-marked variety called chiastolite.