Rock & Mineral Encyclopedia

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

Trapiche Tourmaline

A rare tourmaline showing a fixed wheel-like pattern of color zones and arms radiating from the crystal's center.

A rare blue beryl showing a fixed six-spoke wheel pattern caused by impurity inclusions arranged along the crystal's growth axis.

A feldspar-rich sandstone, often pink, that points to granitic source rocks eroded quickly in dry or cold climates.

Coarse, clear-to-white crystalline calcite that cements limestones, contrasting with fine muddy micrite.

A dark, foliated schist rich in graphite that leaves a grey-black mark and forms from metamorphosed carbon-rich sediments.

A rare iron-rich (ferric) species of the tourmaline group, dark brown to bronze-black, named after crystallographer Martin Buerger.

A rare zirconium-bearing garnet that crystallizes in carbonatites and alkaline rocks, first described from Magnet Cove, Arkansas.

A chromium-rich magnesium garnet of the pyrope series that crystallizes in the deep mantle and is a valuable diamond indicator mineral.

A pale chalcedony agate with cloudy, frost-like white patterning suggesting frost on a window or icy crystalline textures.

Goethite is a common brown iron oxyhydroxide, the main crystalline component of limonite and rust, with shimmering botryoidal forms.

The hardest known natural material, a crystalline form of pure carbon prized as the ultimate gemstone for its brilliance and fire.