Rock & Mineral Encyclopedia

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

Conglomerate

A coarse sedimentary rock of rounded pebbles and gravel cemented in a finer matrix, recording ancient rivers and beaches.

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

Ancient chemically deposited rock of alternating iron-oxide and silica bands recording Earth's early oxygenation and a major iron ore source.

The purple variety of quartz, colored by iron and natural irradiation, prized as the classic violet birthstone of February.

A rare swirling lilac-to-violet silicate found only in Siberia, prized for its fibrous, chatoyant purple patterns.

A man-made glittering glass packed with tiny copper crystals, traditionally reddish-brown but also made in blue and green.

A rare deep-purple manganese-bearing silicate, mostly from South Africa, prized for its vivid violet color.

A copper-iron sulfide ore famous for its iridescent peacock-like purple and blue tarnish; often sold as treated chalcopyrite.

An uncommon purple to violet tourmaline colored by manganese, the deeper reddish-purple stones sometimes called siberite.

A natural bicolor quartz blending amethyst purple with prasiolite green in a single crystal, prized as a metaphysical heart-crown stone.

A vivid Australian jasper-like silica stone in earthy reds, yellows, and purples, formed from silicified radiolarian sediment.