Rock & Mineral Encyclopedia

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

Opal

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

An exceptionally coarse-grained igneous rock, often granitic, famous for hosting large crystals and many gemstones.

The red, chromium-colored variety of corundum, prized as one of the most valuable colored gemstones and second only to diamond in hardness.

A group of silicate gemstones best known for deep red but spanning nearly every color, including green tsavorite and orange spessartine.

The green chromium- and vanadium-colored variety of beryl, one of the four classic precious gemstones renowned for its rich green color.

A striking color-zoned tourmaline with a pink center and green rind, resembling a slice of watermelon when cut across the crystal.