Rock & Mineral Encyclopedia

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

Coober Pedy Opal

Australia's classic light-bodied precious opal from Coober Pedy, famed for milky white stones flashing pastel rainbow play-of-color.

The most common variety of quartz, milky white from microscopic fluid and gas inclusions, forming massive veins worldwide.

Agate that forms in flat cracks or veins of host rock rather than rounded nodules, producing straight, parallel banding.

A pale jasper crossed by distinctive blue-gray veins or lines, valued by lapidaries for its calm color contrast.

Black volcanic glass crossed by a fine network of grey or brown veins that resemble a spider's web.

Siderite is an iron carbonate ore, a brown rhombohedral mineral of the calcite group found in sediments and veins.

Wolframite is the historic principal ore of tungsten, a heavy black tungstate forming bladed crystals in granite veins.

Black volcanic glass laced with delicate web-like veins of contrasting color, formed by flow banding and fine crystallization.

A dark, glassy rock formed when frictional heat from fault movement or impact melts rock along narrow veins.

Precious opal that forms in thin veins within brown ironstone boulders, cut with the host rock left as a natural dark backing.