Peridotites are economically important rocks because they often contain chromite - the only ore of chromium; they can be source rocks for diamonds; and, they have the potential to be used as a material for sequestering carbon dioxide. Much of Earth's mantle is believed to be composed of peridotite.
Many Types of Peridotite
The peridotite “family” contains a number of different intrusive igneous rocks. These include: lherzolite, harzburgite, dunite, wehrlite and kimberlite. See images at right and above. Most of them are an obvious green color attributed to their olivine content.
Lherzolite: a peridotite composed primarily of olivine with significant amounts of orthopyroxene and clinopyroxene. Some researchers believe that much of Earth's mantle is composed of lherzolite.
Harzburgite: a peridotite composed primarily of olivine and orthopyroxene with small amounts of spinel and garnet.
Dunite: a peridotite that is composed mainly of olivine and may contain significant amounts of chromite, pyroxene and spinel.
Source: geology.com