Rock & Mineral Encyclopedia

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

Rainbow Obsidian

A black volcanic glass that reveals concentric rainbow bands of color when cut and polished against the light.

A solid jet-black chalcedony, usually a dyed and treated agate, prized for sleek polished beads, cabochons, and intaglios.

A rare calcium-rich lithium tourmaline famous for the spectacular concentric color zoning seen in polished cross-section slices.

A natural sheen obsidian whose black glass displays a soft, velvety rainbow shimmer from aligned magnetite nanoparticles when polished and tilted.

A manganese aluminum garnet glowing in vivid orange to reddish-orange tones, with the finest called mandarin garnet.