Rock & Mineral Encyclopedia

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

Gray Obsidian

Obsidian in gray tones, often semi-translucent, colored by light scattering and minor inclusions within the volcanic glass.

A dense, high-pressure metamorphic rock famous for its red garnets set in bright green pyroxene, formed deep within subduction zones.

A translucent chalcedony decorated with branching, fern-like manganese or iron oxide inclusions resembling tiny plants.

Obsidian with a hazy, cloud-like translucency caused by uneven distribution of tiny bubbles or incipient crystallites in the glass.

Black volcanic glass with a warm bronze or coppery sheen produced by light reflecting off aligned microscopic inclusions.

A single beryl crystal showing two distinct color zones, such as aquamarine blue grading into morganite pink, within one stone.

A limestone packed with visible shells and shell fragments, recording the accumulation of marine invertebrate remains on ancient sea floors.

A yellow-brown alteration material formed when basaltic volcanic glass reacts with water, common in hydrovolcanic tuffs and pillow lavas.

An intensely blue metamorphic rock of lazurite flecked with golden pyrite, prized for millennia as a gemstone and ultramarine pigment.

A warm golden-brown garnet named for its honey color, typically a hessonite grossular variety with a distinctive treacly internal texture.

A striking platy, blade-like variety of albite feldspar that grows in fanned aggregates of thin white crystals within granite pegmatites.