Rock & Mineral Encyclopedia

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

Zebra Agate

A banded chalcedony agate with bold alternating dark and light stripes resembling zebra markings, sometimes color-enhanced.

A translucent chalcedony agate whose mineral inclusions form miniature scenes resembling mountains, trees, deserts, and skies.

A hard, dark, poorly sorted sandstone with a muddy matrix, typically deposited by underwater turbidity currents.

An opaque green variety of chalcedony quartz colored by iron and chlorite-group inclusions, prized as a durable carving and cabochon stone.

A dark green jasper-chalcedony speckled with red iron-oxide spots, classically known as bloodstone or heliotrope.

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

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

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

Rare precious opal from Tintenbar in northern New South Wales, Australia, occurring in volcanic basalt rather than sedimentary rock.

A fine-grained, dark volcanic rock that erupts as fluid lava and forms most of the ocean floor and many lava plateaus.

A rare emerald showing a six-spoked star pattern of dark inclusions, named after the spokes of a sugar-mill wheel.

Precious opal from Honduras occurring in a dark volcanic matrix, where bright flecks of color flash against a natural black basalt background.

Fine, golden, hair-like strands of basaltic volcanic glass spun from fluid lava droplets during eruptions, named for the Hawaiian volcano goddess.

Small, smooth, teardrop-shaped beads of basaltic volcanic glass formed from airborne lava droplets, often paired with Pele's hair.

A dense, dark ultramafic plutonic rock composed almost entirely of pyroxene minerals, often associated with peridotite and layered intrusions.