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 nodular rhyolite geode-like ball whose plain exterior hides a star-shaped agate or chalcedony core when cut.

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 gray-toned jasper with swirling cream, black, and brown leaf-like patterns, sometimes with druzy or agate pockets.

Tourmaline showing many color zones in a single crystal, often revealing spectacular concentric patterns when sliced.

Abundant banded chalcedony from southern Brazil, the world's main source of agate slices and dyed agate products.

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

Coarse, clear-to-white crystalline calcite that cements limestones, contrasting with fine muddy micrite.