Most diamonds form in which layer of the Earth?

• A. Mantle
• B. Crust
• C. Outer Core
• D. Inner Core

Answer: (A)

Diamonds form under the high-pressure, high-temperature conditions found deep in Earth’s mantle. In the mantle, carbon-bearing rocks experience pressures strong enough for carbon atoms to arrange into the rigid crystal lattice of diamond, rather than staying as graphite. The crust sits at much lower pressure and temperature, where graphite is the more stable form and crystals don’t convert into diamonds. The outer core is a hot, liquid metal, and the inner core is a solid iron sphere; these environments aren’t where mantle-like diamond crystallization occurs. Most diamonds that reach the surface are carried up by deep-origin magmas in kimberlite eruptions, which originate in the mantle. So, the layer where most diamonds form is the mantle.