Peridotiitti

Peridotiitti is an ultramafic igneous rock. It is composed primarily of the minerals olivine and pyroxene. Peridotite is dark-colored, with olivine typically giving it a greenish hue. It is a dense rock, reflecting its high mineral content.

This rock type is believed to be the main component of the Earth's upper mantle. Its presence in the mantle makes it significant for understanding the planet's internal structure and processes. Peridotite can be brought to the surface through tectonic activity, such as during the formation of mountain ranges or through the eruption of certain volcanoes. When peridotite is exposed at the surface, it weathers relatively quickly due to the instability of its constituent minerals under atmospheric conditions.

There are several subtypes of peridotite, classified based on the relative proportions of olivine and pyroxene, as well as the presence of other minerals like spinel or plagioclase. Common types include dunite (almost entirely olivine), harzburgite (olivine and orthopyroxene), lherzolite (olivine, orthopyroxene, and clinopyroxene), and wehrlite (olivine and clinopyroxene).

Peridotite is also a source of valuable minerals. The gemstone peridot is a transparent, green variety of olivine, which can be found in peridotite. While not a common rock in the Earth's crust, its existence in the mantle provides crucial insights into the composition and dynamics of our planet.