Rock & Mineral Encyclopedia

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

Watermelon Tourmaline

A striking color-zoned tourmaline with a pink center and green rind, resembling a slice of watermelon when cut across the crystal.

A green-and-white banded metamorphic marble whose wavy mica layers resemble the rings of a sliced onion.

A nickel sulfide famous for delicate brass-yellow hairlike crystals that form radiating sprays inside cavities and geodes.

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

A magnesium carbonate mineral, usually chalky white with grey veining, widely dyed to imitate turquoise and other stones.

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