Rock & Mineral Encyclopedia

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

Kambaba Jasper

A dark green-and-black stromatolite jasper patterned with swirling orbs, formed from fossilized ancient microbial colonies.

Fossilized wood in which the original organic structure has been replaced by opal, sometimes showing precious play-of-color.

Fossil shells whose original material has been replaced by opal, preserving ancient marine forms in common or precious opal.

A metamorphic rock of calcium-rich silicate minerals formed from impure limestone or dolomite altered by heat and fluids.