How do I identify Peridotite?

Peridotite can be identified by its hardness of 6.5 - 7 on the Mohs scale, Greenish-gray color. Look for these key characteristics when examining specimens.

What color is Peridotite?

Peridotite typically appears in Greenish-gray, black, dark gray, yellowish-green. Color can vary depending on impurities and formation conditions.

How hard is Peridotite?

Peridotite has a hardness of 6.5 - 7 on the Mohs scale. This gives it moderate hardness.

Peridotite

A variety of Igneous

Uncommon

Peridotite specimen - rock identification

What is Peridotite?

Peridotite is an igneous rock easily recognized by its deep olive coloration (the rock’s name is derived from the similarly-colored gemstone, peridot). Commercially valuable, this rock is the only known source of chromite, an ore of chromium, which is used in manufacturing stainless steel. Platinum, nickel, diamonds, and gemstone-quality garnet may also be found embedded within peridotite.

Uses & Applications

Peridotite is a source of many gemstones, including diamonds. It is also a source of chromium and platinum ore, popularly used metal alloys, as well as talc which is commonly used in baby powder, cosmetics, and chalk. Peridotite may also be a good source of other minerals and elements, including iron, nickel, and cobalt.

Peridotite Market Value Calculator

Estimate the market value of Peridotite using size, quality, and finish. This preview calculator is for quick context and is not a formal appraisal.

Peridotite Localities Map

See where Peridotite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.

Map preview

North ZoneCentral RidgeSouth Basin

Key Characteristics

Rock Types of Peridotite

Dunite: more than 90% olivine, typically with Mg/Fe ratio of about 9:1. Wehrlite: mostly composed of olivine plus clinopyroxene. Harzburgite: mostly composed of olivine plus orthopyroxene, and relatively low proportions of basaltic ingredients (because garnet and clinopyroxene are minor). Lherzolite: most common form of peridotite, mostly composed of olivine, orthopyroxene (commonly enstatite), and clinopyroxene (diopside), and have relatively high proportions of basaltic ingredients (garnet and clinopyroxene). Partial fusion of lherzolite and extraction of the melt fraction can leave a solid residue of harzburgite.

Formation of Peridotite

Peridotite have two primary modes of origin, as mantle rocks formed during the accretion and differentiation of the Earth, or as cumulate rocks formed by precipitation of olivine ± pyroxenes from basaltic or ultramafic magmas; these magmas are ultimately derived from the upper mantle by partial melting of mantle peridotites.

Composition of Peridotite

Olivine is a magnesium orthosilicate containing some iron with the variable formula (Mg,Fe)2SiO4; the pyroxenes are chain silicates having the variable formula (Ca,Na,Fe,Mg)(Cr,Al,Fe,Mg,Mn,Ti,V)Si2O6 comprising a large number of different minerals. Magnesium-rich olivine forms a large proportion of peridotite, and so magnesium content is high. Layered igneous complexes have much more varied compositions, depending on the fractions of pyroxenes, chromite, plagioclase, and amphibole.