There are many unsolved mysteries surrounding diamonds, and while most are produced by hand (e.g. De Beers), some are all-natural. Recent findings by researchers suggest that impressive diamonds such as Hope Diamond may have originated in deeper mantles than previously thought.
Most diamonds form in the upper mantle, just below the continental crust, at depths of between 150 and 200 kilometers (93 to 124 miles). In rare cases, diamonds can also form deeper underground, with an estimated depth of between 360 and 750 kilometers (224 to 466 miles).
The conditions for the formation of diamonds are rare and harsh, and carbon atoms crystallize into precious diamonds at such extreme temperatures as the mantle (1000 degrees-1300 degrees) and extremely high pressure (4500-60,000 atmospheres). The geographical environment of the mantle is stable and is very conducive to the formation of diamonds, known as “the home of diamonds”.
The Gemological Institute of America (GIA) recently found this new evidence. The team studied two large diamonds — a 20-carat IIb blue diamond found in South Africa and a 124-carat CLIPPIR diamond from Lesotho. Using spectrometers, they found the remains of a mineral called Bridgeman Stone.
Evan Smith, of GIA, says: “Bridgeman stone does not exist in the upper mantle, nor does it exist on the surface. When a diamond reaches the surface, what we actually see in the diamond is not bridgestone, but the minerals it leaves behind as it breaks down as the pressure decreases. The discovery of these minerals in diamonds means that the diamond itself must have crystallized at the depth where the bridgestone is present, deep in the earth. “
“Discovering the origins deep in the mantle means that the materialin in these diamonds has gone through an extraordinary journey,” says Smith. We believe that the blue boron, which gives hope diamonds, comes from the bottom of the ocean. From there, plate tectonics drag it into hundreds of kilometers of mantle, where it can fit into diamonds. This suggests that there is a huge circular route that brings elements of the Earth’s surface into the Earth and then occasionally returns beautiful diamonds to the ground as a passenger of volcanic eruptions. “