Small pieces of peridotite have even been found in lunar breccias. The rocks of the peridotite family are uncommon at the surface and are highly unstable, because olivine reacts quickly with water at typical temperatures of the upper crust and at the Earth's surface.

Where is peridotite most common?

Peridotite is generally believed to be the most common rock found in the upper mantle of the Earth. The medium- to coarse-grained intrusive igneous material does occur in several different forms and environments, however, including layered complexes, sills, irregular masses, dikes, and volcanic pipes.

Why is peridotite not considered a mineral?

Alteration of Peridotite

Peridotite is a rock type that is more representative of Earth's mantle than of the crust. The minerals that compose it are generally high-temperature minerals that are unstable at Earth's surface. They are quickly altered by hydrothermal solutions and weathering.