World Rare 555.55-carat black diamond, thought to be forged in space, to be sold at online auction January 19, 2022January 19, 2022 Gabriela Miranda, USA TODAY Comments Off on Rare 555.55-carat black diamond, thought to be forged in space, to be sold at online auction A rare 555.55-carat black diamond, named "The Enigma," has been listed for auction by Sotheby's and is expected to sell for over $6 million.