Rock & Mineral Encyclopedia

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

Jaspillite

A banded, metamorphosed iron formation in which bright red jasper alternates with silvery hematite or magnetite layers.

Quartz containing visible internal crystal outlines, formed when growth paused and trapped a layer of mineral inclusions.

A hardened soil crust cemented by calcium carbonate, forming a tough whitish layer common in arid and semi-arid regions.

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

A banded chalcedony combining reddish-brown sard with white or black onyx layers, prized since antiquity for carved cameos.

A rare brown chalcedony containing thin iron-oxide layers that produce flashing, fiery rainbow iridescence like trapped flames.

A synthetic garnet-structured oxide (YAG) used as a diamond simulant and laser crystal, with no natural counterpart.