Rock & Mineral Encyclopedia

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

Kimberlite

A rare ultramafic volcanic rock that erupts from deep in the mantle and is the primary natural source of diamonds.

A chromium-rich magnesium garnet of the pyrope series that crystallizes in the deep mantle and is a valuable diamond indicator mineral.

A rare ultrapotassic, magnesium-rich volcanic rock from deep in the mantle, famous as the diamond host at Argyle in Australia.

Fossil shells whose original material has been replaced by opal, preserving ancient marine forms in common or precious opal.