Rock & Mineral Encyclopedia

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

Cathedral Agate

A banded agate whose internal structures resemble cathedral spires, arches, or a city skyline of towers and pinnacles.

A translucent chalcedony agate containing delicate, feather- or plume-shaped mineral inclusions that branch like soft feathers.

An opaque blue variety of chalcedony jasper, less common than red or green forms, colored by mineral inclusions.

A rock formed from hot pyroclastic flows, often welded, sometimes containing flattened glass lenses called fiamme.

A rare, ancient ultramafic volcanic rock formed from extremely hot magma, famous for its spinifex texture.

Rutile is a major titanium ore and the famous golden needle inclusion that gives rutilated quartz its shimmering threads.

A vivid blue-green hydrated copper silicate, soft on its own but prized as a gem when hardened by intergrown quartz or chalcedony.

A soft, green, foliated rock rich in chlorite, formed by low-grade metamorphism of mafic or volcanic rocks.

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