Hidden 410 kilometers away in the Earth's mantle, somewhere between the crust and the core, it is suspected that there is a reservoir of diamonds as old as our natural satellite, according to a new study carried out by the Australian National University.
These diamonds would be in a large reserve of relatively intact rock since the formation of the planet, safe from the violent geological activity and extraterrestrial impacts that hit Earth.
To identify diamonds have not been observed directly, but through geochemical traces. Specifically, they have measured helium isotopes contained in super-deep diamonds brought to the surface by violent volcanic eruptions, to detect the traces of this ancient deposit.
Most diamonds form between 150 and 230 kilometers below the earth's crust, before being melted on the surface. Very occasionally, some super-deep diamonds (created between 230 and 800 kilometers below the Earth's surface) are brought to the surface and are different from normal diamonds. As explained by the research leader Suzette Timmerman:
Diamonds are the hardest and most indestructible natural substance known, so they form a perfect time capsule that gives us a window to the deep Earth. We were able to extract helium gas from twenty-three super-deep diamonds from the Juína area in Brazil. (…) There are questions about the form of this deposit; Is it a large single reservoir or are there several smaller old reservoirs? Where exactly is the deposit? What is the complete chemical composition of this deposit?