Rock & Mineral Encyclopedia

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

Lherzolite

The most common type of mantle peridotite, made of olivine with both orthopyroxene and clinopyroxene, representing fertile upper-mantle rock.

An opaque grey-brown common opal forming nodules and concretions, historically called liver opal for its dull brownish color.

Fossil shells whose original material has been replaced by opal, preserving ancient marine forms in common or precious opal.