Here's a breakdown:

* Ultramafic rocks are igneous rocks with a very low silica content (less than 45%) and are rich in magnesium and iron.

* The most common ultramafic rocks in the mantle are peridotite and dunite.

* Peridotite is a coarse-grained rock that typically contains olivine, pyroxene, and other minerals.

* Dunite is a type of peridotite that is almost entirely composed of olivine.

While the mantle is mostly made of ultramafic rocks, there are other types of rocks present, including:

* Eclogite: A metamorphic rock formed from basalt under high pressure and temperature.

* Granulite: A metamorphic rock that can form from a variety of parent rocks.

It's important to note that the composition of the mantle can vary with depth. The upper mantle is predominantly peridotite, while the lower mantle is thought to be primarily composed of bridgmanite, a dense mineral that forms under extreme pressure.