Rock & Mineral Encyclopedia

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

Chalcocite

A dark gray copper sulfide that is one of the richest copper ores, prized by collectors when found as rare sharp crystals.

A reddish-brown rare-earth phosphate that is a primary ore of cerium, thorium and other rare-earth elements, often found in placer sands.

Agate that was shattered and naturally re-cemented by silica, creating a mosaic of angular fragments in a quartz matrix.

Tabular quartz crossed by a milky white thread-like line marking where the crystal repeatedly cracked and re-healed.