Rocks in the mantle have a specific gravity of 3.3. Any material with s specific greater than 1 means that it is more dense than water. The mantle, making up 84% of the earth's volume, is a ductile and viscous layer of the earth that is located between the core and crust. It is composed of many elements such as: oxygen, magnesium, silicon, iron, calcium, aluminum, sodium, and potassium.