peridotiitissa

Peridotite is an ultramafic igneous rock that forms from the slow crystallization of magma composed of olivine, orthopyroxene, and clinopyroxene. It is primarily found in the Earth's mantle and is rarely exposed at the surface, typically brought up through tectonic processes such as obduction or volcanic activity. The name "peridotite" originates from the Greek word *peridōtos*, meaning "to bring forth," likely referencing the green gemstone peridot, which is a variety of olivine often found within peridotite.

Peridotite is characterized by its dark green to black color, resulting from the high iron and magnesium content in its minerals. Olivine is the dominant mineral, often making up over 50% of the rock, with pyroxenes (both orthopyroxene and clinopyroxene) comprising the remainder. Trace amounts of minerals like spinel or garnet may also be present, depending on the specific type of peridotite. The rock is classified into two main varieties: dunite, which is nearly pure olivine, and harzburgite, which contains significant amounts of orthopyroxene.

Peridotite plays a crucial role in geology as a key component of the Earth's mantle. It is also economically significant as a source of chromite, a mineral used in metallurgy, and as the primary host rock for peridot, a gemstone prized for its vibrant green hue. Due to its deep mantle origin, peridotite provides valuable insights into the composition and processes of the Earth's interior. Samples of peridotite are often studied to understand mantle convection, partial melting, and the formation of volcanic rocks.