What is the mantle made of?
We know the composition of the uppermost mantle because we have samples of it. There are no known samples from the lower mantle. The only way to determine its mineralogy and structure is to observe the speed of seismic waves, and to re-create deep-mantle conditions in the laboratory.
As depth increases, the minerals that make up the mantle become more dense, or compact. For example, the common mineral olivine changes to the more compact structural forms of spinel and then perovskite.
Topic: Earth Science
Subtopic: Earth Structure
Keywords: Geology, Stratigraphic, density, Rocks, Earth (Planet)--Mantle, Seismology