Rock & Mineral Encyclopedia

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

Eye Agate

A chalcedony agate marked by round, concentric ring patterns that resemble eyes when cut and polished.

Black volcanic glass marked with rounded spots and patches that resemble a leopard's coat, caused by spherulitic crystallization.

Glacially deposited banded agates found along Lake Michigan beaches, small waterworn pebbles with concentric red and grey banding.

Limestone built from tiny rounded ooid grains resembling fish roe, formed in warm, agitated shallow seas.

A rare agate that forms naturally with flat polygonal faces and angular geometric shapes rather than the usual rounded nodule.