Peridotite

Peridotite Classification and Composition

Peridotite is a coarse-grained ultramafic rock with olivine making up 40% or more of the total volume.
Coarse-grained igneous rocks with over 90% mafic minerals are classified as ultramafic rocks.
Ultramafic rocks contain less than 45% silica.
Dunite contains more than 90% olivine and is found in ophiolites and layered intrusions.
Kimberlite is formed in volcanic pipes and contains at least 35% olivine.
Mantle peridotite is highly enriched in magnesium, with a typical magnesium number of 89.
Olivine is the essential mineral found in all peridotites, typically olive-green in color.
Pyroxenes are chain silicates, divided into orthopyroxenes and clinopyroxenes.
Hornblende is an amphibole mineral present in peridotite due to alteration by hydrous fluids.
Other accessory minerals in peridotites include chromite, spinel, garnet, biotite, and magnetite.

Peridotite is the dominant rock of the upper part of Earth's mantle.
Peridotite nodules found in certain basalts provide samples of Earth's mantle brought up from depths ranging from 30km to 200km or more.
Peridotite outcrops range in color from earthy bright yellow to dark green.
Peridotite is found in ophiolites, which are interpreted as slices of oceanic lithosphere thrust onto continents.
Peridotite is also found in volcanic pipes and is known for being the host rock to diamonds.

Dunite contains more than 90% olivine and is found in ophiolites and layered intrusions.
Harzburgite contains less than 5% clinopyroxene and makes up the bulk of the peridotite layer of ophiolites.
Wehrlite contains less than 5% orthopyroxene and is found in the transition zone between the peridotite layer and overlying gabbro layer of ophiolites.
Lherzolite has an intermediate content of clinopyroxene and orthopyroxene, making it a likely source rock for basaltic magma.
Hornblende peridotite contains from 40% to 90% olivine and less than 5% pyroxene, found as rare xenoliths in andesites above subduction zones.

Classic peridotite is bright green with some specks of black.
Peridotitic outcrops range in color from earthy bright yellow to dark green.
Peridotitic rocks may exhibit a wide range of colors including blue, brown, and red.
Peridotite hand samples tend to be darker green.
Peridotite contains accessory minerals like chromite, which can affect the color of the rock.
Peridotite weathers to form a distinctive brown crust in subaerial exposures.
Peridotites can take on a massive form or may be in layers on a variety of size scales.
Layered peridotites may form the base layers of layered intrusions.

Peridotites 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.
Mantle peridotites are sampled as ophiolites in collisional mountain ranges, as xenoliths in basalt or kimberlite, or as abyssal peridotites.
Alpine peridotites may be either of the ophiolite association or masses of subcontinental mantle emplaced along thrust faults in mountain belts.
Layered peridotites are igneous sediments and form by mechanical accumulation of dense olivine crystals.
Komatiites are high temperature partial melts of peridotite characterized by a high degree of partial melting deep below the surface.
Eclogite is a rock similar to basalt in composition and is associated with peridotite in some xenolith occurrences.
Peridotite may potentially be used in a low-cost method of capturing and storing atmospheric CO.
Peridotite is named for the gemstone peridot.
Layered intrusions with cumulate peridotite are typically associated with sulfide or chromite ores.

Reference	URL
Glossary	https://harryandcojewellery.com.au/blogs/glossary/peridotite
Wikipedia	http://en.wikipedia.org/wiki/Peridotite
Wikidata	https://www.wikidata.org/wiki/Q239918
Knowledge Graph	https://www.google.com/search?kgmid=/m/030c8l