Rock & Mineral Encyclopedia

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

Cipollino Marble

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

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.