peridotite

Peridotite is an important but often unseen igneous rock, meaning it formed from molten material that cooled and solidified. Unlike rocks such as granite or basalt, which are common in the Earth's crust, peridotite mainly makes up the Earth's upper mantle below the crust we live on. It is a dense, coarse-grained rock, usually dark greenish in color because it contains a lot of olivine, along with minerals such as pyroxene.

The name "peridotite" comes from peridot, a gemstone variety of olivine. This rock is not usually used for building or decoration because it normally remains deep underground. Even so, it matters a great deal to geologists because it helps them understand the mantle, plate tectonics, and the processes that feed volcanoes. Pieces of peridotite sometimes reach the surface in volcanic pipes such as kimberlites, which can also carry diamonds.

Geologists study peridotite because it offers clues about Earth's interior, as well as the planet's formation and long history. In that sense, it acts like a window into the deep Earth. When scientists find it at or near the surface, they can learn about places that are otherwise far beyond our reach. So when you think about mountains, volcanoes, or drifting continents, it helps to remember that deep below them lies peridotite, one of the main rocks of our planet's interior.