A diamond, which is the main attribute of the British Crown Jewels, could have originated from much deeper into the Planet than considered before.
Diamonds emerge from deep in the Earth ‘s surface as carbon atoms crystallize under extreme heat and pressure over billions of years.
Many diamonds form at around 150 km (93 miles) to 200 km (124 miles) under the surface of the Planet, and the deeper the diamond, the more precious it becomes as they are more compact and weigh more as a result, with the weight of a diamond as a carat (equal to 200 milligrams).
The Cullinan’s new analysis, the largest diamond ever found cut to make up part of the Crown Jewels, found it could originate from below the surface up to 750 km (466 miles).
This would make the jewel that the Transvaal government-a former province of South Africa-gave to King Edward VII in 1907 after the Boer War, more valuable than previously thought.
Researchers at the Gemological Institute of America (GIA) likened the Cullinan to the Smithsonian’s Hope diamond and the Lesotho stone-a super-deep, 124 carat diamond from a South African mine.
Dr Evan Smith, of GIA, who conducted the research, said: “We examined the first large gem diamonds confirmed to originate from Earth’s lower mantle, which is several times deeper than most other diamonds.
“The results support earlier predictions based on smaller gems, suggesting that diamonds with properties similar to those studied, including both the Cullinan and Hope diamonds, are super-deep diamonds.”
“It’s very common in the deep Earth, at the extreme pressure conditions of the lower mantle, below a depth of 660km, even deeper than most super deep diamonds.
“Bridgmanite doesn’t exist in the upper mantle, or at the surface.
“What we actually see in the diamonds when they reach surface is not bridgmanite, but the minerals left when it breaks down as the pressure decreases.
“Finding these minerals trapped in a diamond means that the diamond itself must have crystallised at a depth where bridgmanite exists, very deep within the Earth.”
