A billion-year-old black diamond, believed to be the largest cut in the world, was bought with cryptocurrencies at an auction for $4.3 million, according to CNBC․

Known as the Enigma, the natural-colored fancy black diamond, weighing 555.55 carats, was on display in London from February 2 to 9, according to Sotheby's.

The auction house confirmed on Twitter that the black diamond was purchased with cryptocurrency. Sotheby’s did not name the buyer, but entrepreneur Richard Hart tweeted that he bought the diamond and will rename it the “HEX.com diamond” after his blockchain certificate of deposit business.

In 2006, Enigma was named the world's largest cut diamond by the Guinness Book of Records. Sotheby's called the diamond one of the rarest billion-year-old wonders known to mankind.

This particular type of black diamond is believed to have been created either by meteorite impacts that cause natural chemical vapor deposition, or extraterrestrial origin from supernova explosions that formed diamond-bearing asteroids that eventually collided with Earth, Sotheby’s explained.