Rock & Mineral Encyclopedia

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

Calcite

An extremely common calcium carbonate mineral that comes in nearly every color and shows strong double refraction in clear crystals.

A very soft sulfate mineral defining Mohs 2, occurring as selenite, satin spar, alabaster, and desert rose, used to make plaster.

A trade name for pink garnets, mainly rhodolite, a rose-to-purplish pyrope-almandine blend prized for its bright clean color.

A transparent yellow to golden gem variety of labradorite feldspar, usually faceted to show its clear, warm color.

Opal from Oregon, USA, ranging from translucent blue Owyhee opal to clear and fiery contra-luz precious opal from Opal Butte.

Translucent smoky-gray obsidian that transmits a hazy light, intermediate between clear and fully black volcanic glass.

The blue iron-bearing variety of beryl, forming clear hexagonal crystals prized both as specimens and as a March birthstone gem.