Rock & Mineral Encyclopedia

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

Mahogany Obsidian

A natural volcanic glass with rich brown and black mahogany-like swirls created by iron oxide inclusions.

Black volcanic glass dotted with radiating spherulite bursts that look like exploding fireworks frozen in the stone.

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

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

A general term for light-colored, fine-grained volcanic rocks rich in quartz and feldspar, like rhyolite.

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

A lustrous black titanium-rich garnet of the andradite series, found in alkaline igneous rocks like nepheline syenite and ijolite.