Dubbed "The Enigma", the 555.55-carat rock is the star of a Sotheby's auction open for bidding online from 3 to 9 February.

The "true natural phenomenon" is the biggest faceted diamond of any kind to appear at any auction.

It was listed as the largest cut diamond in the world in the 2006 Guinness Book of World Records.

Sotheby's says that a natural faceted black diamond of such size is extremely rare, and the diamond's origins are "shrouded in mystery".

It is thought to have been created either from a meteoric impact or possibly emerged from a diamond-bearing asteroid that collided with Earth.

Its shape is inspired by the Middle Eastern palm-shaped symbol, the Hamsa - a sign of protection, power and strength.

The Hamsa is also associated with the number five, which is symbolic since the diamond is not only 555.55 carats in size, but it also contains exactly 55 facets.

Previously unseen on the market, The Enigma was first exhibited to the public in Dubai, Los Angeles and London before being put up for auction.

Cryptocurrency will be accepted as payment, Sotheby's said, in a move that reflects the fact it has started to make its mark in the world of physical art and objects.

'Cosmic wonder'

Sotheby's Jewellery Specialist Nikita Binani said the diamond is a "unique and precious object of curiosity".

She added: "This diamond has been treasured for over two decades by the owner, and the diamond itself has never been exhibited publicly or offered on the open market, so we are thrilled to have the opportunity to tell its story to the world.

"Its sale represents a once-in-a-lifetime opportunity to acquire one of the rarest, billion-year-old cosmic wonders known to humankind."

Meanwhile, Katia Nounou Boueiz, Head of Sotheby's UAE, said: "We are honoured that Dubai has been chosen as the first stop for this exceptional rarity and are thrilled to play a part in its journey, which began so many millions of years ago."