Rock & Mineral Encyclopedia

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

Purple Sheen Obsidian

Black volcanic glass that reveals a soft purple-to-violet sheen at certain angles, caused by light interference off aligned inclusions.

Quartz with a stepped, multi-pointed structure of parallel side crystals resembling the spires of a cathedral.

The golden-yellow variety of quartz, ranging from pale lemon to deep madeira amber, often produced by heating amethyst.

A purple-hued common opal, much of it the Mexican "morado" type, valued for even violet color rather than play-of-color.

A trade name for quartz containing a combination of seven minerals including amethyst, smoky quartz, and cacoxenite, prized by collectors.

A quartz with a main point surrounded by many smaller crystals along its sides, resembling melted candle wax, mainly from Madagascar.

A feldspar-rich sandstone, often pink, that points to granitic source rocks eroded quickly in dry or cold climates.