DUBAI, United Arab Emirates — Auction house Sotheby’s Dubai has unveiled a diamond that’s literally from out of this world.

Sotheby’s calls the 555.55-carat black diamond — believed to have come from outer space — “The Enigma.” The rare gem was shown off on Monday to journalists as part of a tour in Dubai and Los Angeles before it is due to be auctioned off in February in London.

The Enigma is the largest “Fancy Black Natural Colour” diamond in the world, according to the auction house.

Sotheby’s expects the diamond to be sold for at least $6.8 million. The auction house plans to accept cryptocurrency as a possible payment as well.

Sophie Stevens, a jewelry specialist at Sotheby’s Dubai, said that the number five bears an importance significance to the diamond, which has 55 facets as well.

“The shape of the diamond is based on the Middle Eastern palm symbol of the Khamsa, which stands for strength and it stands for protection,” she said. Khamsa in Arabic means five.

“So there’s a nice theme of the number five running throughout the diamond,” she added. Stevens also said the black diamond is likely from outer space.

“With the carbonado diamonds, we believe that they were formed through extraterrestrial origins, with meteorites colliding with the Earth and either forming chemical vapor disposition or indeed coming from the meteorites themselves,” she said.

Black diamonds, also known as carbonado, are extremely rare, and are found naturally only in Brazil and Central Africa. The cosmic origin theory is based on their carbon isotopes and high hydrogen content.

The auction house said its decision to accept cryptocurrency for payment reflects, “the fact that cryptocurrency has started to make its mark in the world of physical art and objects.”

In July, Sotheby’s set the high mark for a gemstone bought with cryptocurrency when it sold a  101.38-carat, pear shaped diamond known as The Key 10138 for $12.3 million to an undisclosed buyer.

Bidding on The Enigma opens Feb. 3 online. The gem is being offered without reserve, meaning there is no minimum price to achieve on the bidding in order to sell.