"We are very excited to mention that this diamond has been recorded … as one of the largest fancy black diamonds and also the largest cut diamonds ever to be recorded and known in the world," she added.
The Enigma was listed as the world's largest cut diamond by the Guinness Book of World Records in 2006.
Unlike most diamonds formed deep within Earth, carbonados are found in alluvial, sedimentary deposits, close to or on Earth's surface, the auction house explained.
"This, and their specific mineral make up suggest possible extra-terrestrial origins, either from meteoric impacts producing natural chemical vapor deposition or from diamond-bearing asteroids colliding with the Earth."
The diamond "surpasses the weight of both the Great Star of Africa, 530.2 carats, and the Golden Jubilee, 545.67 carats, making it not only one of the largest fancy black natural-color diamonds in the world, but also the largest faceted diamond to ever appear on the auction market."
Black diamonds are thought to have been formed from a meteoric impact or diamond-bearing asteroid that collided with Earth approximately 3.8 billion years ago, and believed to be a rare natural occurrence only found in Brazil and the Central Republic of Africa.
The diamond will receive online bids between Feb. 3 and 9.
