Here's a breakdown:

* Peridotite: This is the most common rock type in the middle mantle. It's a dense, dark-colored rock composed mainly of olivine and pyroxene, with smaller amounts of other minerals like garnet and spinel.

* Olivine and Pyroxene: These are the dominant minerals in peridotite. They are both silicate minerals, meaning they contain silicon and oxygen.

* Garnet and Spinel: These minerals become more abundant with depth in the middle mantle, replacing olivine and pyroxene due to increasing pressure and temperature.

It's important to note that the exact composition of the middle mantle is not perfectly understood because it's impossible to directly access it. Scientists infer its composition through studying seismic waves, volcanic rocks, and laboratory experiments.