Diamond accounts for three-quarters of this planet's mass?

This is False

Explanation:

The Earth is the third planet from the sun. It has a mass of 5.972 * 10^24 kg.

About 90 percent of the mass of the Earth is composed of elements and compounds such as iron-nickel alloy (95% iron) in the core (30%), and the silicon dioxides (c. 33%) and magnesium oxide (c. 27%) in the mantle and crust. Diamond doesn't account for three-quarters of the planet's mass.