Rock & Mineral Encyclopedia

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

Flint

A hard, dark variety of chert that knaps into razor-sharp edges and sparks against steel, central to Stone Age technology.

Obsidian crossed by parallel flow bands of differing color, formed as layers of lava with slightly different compositions froze into glass.

A hard, fine-grained sedimentary silica rock that breaks with sharp conchoidal edges, prized by ancient toolmakers.

The classic agate defined by concentric or parallel bands of chalcedony in varied colors, the archetype of all agate varieties.

A solid jet-black chalcedony, usually a dyed and treated agate, prized for sleek polished beads, cabochons, and intaglios.

Volcanic glass marked by parallel or swirling bands of differing color that record the flow layering of cooling lava.

A banded jasper showing parallel ribbon-like stripes of contrasting color formed by layered silica and mineral deposition.

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

A black volcanic glass threaded with delicate grey, swirling lace-like bands of flow lines that show beautifully when polished.

A fractured and re-cemented agate whose angular broken bands resemble crumbling walls and ruined cityscapes when polished.

A black volcanic glass that reveals concentric rainbow bands of color when cut and polished against the light.

A banded chalcedony with straight, ribbon-like parallel layers, often cut across the bands for striking striped cabochons.

Black volcanic glass that flashes flame-like bands of iridescent color when light strikes aligned nanoscale inclusions.

A black-and-white striped chalcedony-quartz rock whose bold zebra-like banding makes it a popular ornamental and lapidary stone.