On February 3rd, 2022, a billion-year-old black diamond was purchased with cryptocurrency for £3.16 million (about $4.3 million) in an auction in London, United Kingdom.

This black diamond, referred to as "The Enigma," has a weight of 555.55 carats, and was shown in London between the dates of Feb. 2 and Feb. 9. The diamond, renamed as "HEX.com diamond," was considered to be the world's biggest diamond in 2006, per the Guinness Book of World Records.

According to auctioneer Sotheby's, the diamond is "one of the rarest, billion-year-old wonders known to mankind."

"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 adds in its description.

Although Sotheby's did not pinpoint the exact buyer, after the auction was over, cryptocurrency entrepreneur Richard Heart announced on his Twitter (TWTR  ) account that he had in fact been the one to purchase The Enigma, or "HEX.com diamond," which he had renamed it to.

This diamond is a carbonado, which is one of the most durable forms of natural diamond. They are incredibly rare finds, and are typically only discovered in Brazil or the Central African Republic. They are formed of randomly-oriented diamond grains which absorb more light than typical diamonds, giving them their black appearance. They also are generally around 2.6 to 3.8 billion years in age.

According to Sotheby's, the particular make of carbonados means that they are incredibly challenging to cut or polish, however. It took over three years to mold The Enigma into its present form, and in its original make, was considered to be over 800 carats in weight. As previously mentioned, there are various opinions regarding the origination of the diamond, especially that it was carried to the Earth by an asteroid.