- The fancy, natural color black diamond, known as "The Enigma," weighs 555.55 carats, according to Sotheby's.
- "The Enigma" was named the world's largest cut diamond as of 2006.
LONDON — A billion-year-old black diamond, which is thought to be the largest cut in the world, was bought using cryptocurrency in an auction for £3.16 million ($4.3 million).
The fancy, natural color black diamond, known as "The Enigma," weighs 555.55 carats, according to Sotheby's, and was displayed in London between Feb. 2-9.
The auction house confirmed in a tweet on Wednesday that the black diamond had been bought using cryptocurrency. Sotheby's did not name the buyer but entrepreneur Richard Heart tweeted that he had won the diamond and would be renaming it the "HEX.com diamond," after his blockchain deposit certificate business.
"The Enigma" was named the world's largest cut diamond as of 2006, in the Guinness World Book of Records. Sotheby's called the diamond "one of the rarest, billion-year-old wonders known to humankind."
"The Enigma" is a carbonado diamond, which is found in deposits close to, or on, the Earth's surface, indicating that it could have come from space.
"It is thought that this specific type of black diamond was created either from meteoric impacts producing natural chemical vapor deposition or an extraterrestrial origin — from supernovae explosions that formed diamond-bearing asteroids which ultimately collided with the Earth," Sotheby's explained.
Most other diamonds are found deep within the Earth, while carbonados lack the minerals contained in those precious gems. According to Sotheby's, carbonados contain traces of nitrogen and hydrogen, which are abundant in interstellar space, as well as osbornite, which is found in meteors.
Carbonados typically range from around 2.6 to 3.8 billion years old — the Earth is 4.5 billion years old.
They are only now found in Brazil or the Central African Republic, which were connected for more than a billion years, forming part of what was then known as the supercontinent of Rodinia. Sotheby's said this adds to the theory that carbonados come from space, as it was while they formed part of this supercontinent that the area was believed to have been struck by meteorites.
Carbonados are formed of randomly-orientated, tiny diamond grains, which absorb more light and create their black appearance.
The structure of carbonados makes them nearly impossible to cut and polish, according to Sotheby's, and it took more than three years to shape this diamond into its current form. "The Enigma" was thought to have weighed over 800 carats in its rough form.