Peridotite

Peridotite is a coarse-grained ultramafic igneous rock composed mainly of olivine and pyroxene. It is the dominant rock of Earth's upper mantle.

Olivine: Olivine is a magnesium-iron silicate mineral common in mafic and ultramafic rocks. It is usually peridotite's most abundant mineral and records its magnesium-iron composition.
Partial melting: Partial melting is the extraction of melt from a rock while some solid minerals remain. It removes melt from mantle peridotite and changes the composition of the residue.
Ophiolite: An ophiolite is a fragment of oceanic lithosphere emplaced onto continental crust. Its mantle section can expose peridotite at Earth's surface.
Earth's mantle: Earth's mantle is the thick layer of silicate rock between the crust and the core. Peridotite makes up most of the mantle's upper portion.
Pyroxenite: Pyroxenite is an ultramafic rock composed predominantly of pyroxene. It has much less olivine than the rocks classified as peridotite.
Pyroxene: Pyroxene is a group of rock-forming silicate minerals built from single chains of silica tetrahedra. Its orthopyroxene and clinopyroxene varieties combine with olivine to define many peridotites.
Melt extraction: Melt extraction is the separation and movement of liquid magma away from its source rock. Its efficiency determines whether melting leaves depleted peridotite behind.
Xenolith: A xenolith is a fragment of older rock enclosed within an igneous rock. Mantle xenoliths carried by magma bring peridotite samples to the surface.
Mohorovičić discontinuity: The Mohorovičić discontinuity is the seismic boundary between Earth's crust and mantle. Peridotite commonly lies beneath this boundary in oceanic and continental lithosphere.
Gabbro: Gabbro is a coarse-grained mafic igneous rock composed chiefly of plagioclase and pyroxene. Unlike peridotite, it is dominated by feldspar and typically represents oceanic crust.

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