Rock & Mineral Encyclopedia

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

Dunite

An ultramafic intrusive rock made almost entirely of olivine, representing mantle material.

A dense, coarse-grained ultramafic rock rich in olivine that makes up most of the Earth's upper mantle.

A depleted mantle peridotite of olivine and orthopyroxene, the refractory residue left after basaltic melt is extracted from the mantle.

An ultramafic rock of olivine and clinopyroxene, a peridotite variety common as cumulate layers in mafic intrusions.

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

The gem-quality green variety of olivine, peridot is colored by iron and is one of the few gems found in only one color.

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

A mafic plutonic rock of plagioclase and olivine whose mottled appearance earned it the nickname 'troutstone'.

A rare glassy phonolitic lava with rhomb-shaped anorthoclase phenocrysts and olivine, named for Mount Kenya.

A dark, glass-rich volcanic rock of olivine and augite phenocrysts set in a feldspar-free glassy groundmass, named from the Kaiserstuhl region.

The most abundant basalt type on Earth, a silica-saturated subalkaline lava that forms ocean crust and flood basalts.

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

A rare dark ultramafic lamprophyre rich in melilite, biotite and olivine, named for Alnö Island in Sweden.

A variety of pyroxenite composed of both orthopyroxene and clinopyroxene with little olivine, found in layered intrusions and the mantle.