The largest cut black diamond in the world – yours for €5m

Close to four billion years old, it took three years to produce its current unique shape

A 55-faceted gemstone, believed to be the largest cut black diamond in the world, will be offered in Sotheby’s Enigma sale which opens this Thursday, February 3rd, and ends Wednesday, February 9th.

Weighing 555.55 carats, which is about the same as a deck of cards, the stone is expected to sell for about £5 million, or close to €6 million, because of its unusual shape, colour and weight. Unveiled this week in Dubai, the theme of the number five running throughout the diamond is said to be based on the Middle Eastern palm symbol of the Khamsa, which means quintet in Persian.

Known as a carbonado diamond, it appears much darker than other black diamonds due to its light-absorbing structure, which is due in part to minerals such as graphite that cloud the stone. The auction house says the diamond is the "largest fancy black natural colour diamond in the world as of 2004" – as per the Guinness World Records, and "the largest cut diamond in the world as of 2006" as it surpasses both the Great Star of Africa (the Cullinan Diamond) and the Golden Jubilee, owned by Queen Elizabeth and the King of Thailand respectively.

While there is no doubt as to its size and rarity, it is causing something of a debate among mineralogists, geoscientists and diamond experts as to its origins. Calling it “a treasure from interstellar space”, Sotheby’s is basing this theory on the fact that carbonado diamonds are found in deposits much closer to the earth’s surface – rather than rock formed deep within the earth as is the case for other natural diamonds – adding “it is thought that this specific type of black diamond was created either from meteoric impacts producing natural chemical vapour deposition or an extra-terrestrial origin”.

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‘Not of this earth’

The auction house says the presence of the mineral osbornite, which is uniquely found in meteors, is further indication that the Enigma is not of this earth, and is the result of “supernovae explosions that formed diamond-bearing asteroids that collided with the earth”. Believed to be close to four billion years old, and found exclusively in Brazil and the Central African Republic, the diamond was purchased in the late 1990s and would have weighed in excess of 800 carats in rough form. The consignor says it took three years to produce its current unique shape.

Sceptics include Tim McCoy, curator of the meteorite collection at the Smithsonian National Museum of Natural History, who is “not sure if it came from outer space” and also suggested in an interview with Washington-based NPR (National Public Radio) that it could also have been formed underground 4 billion years ago.

Whatever its origins – be it from outer space or deep within the earth – it’s very old, the biggest of its kind and unique. A replica of this diamond, which was exhibited at the 2010 Shanghai Expo, was viewed by 71 million people in a six-month period.

The Enigma certainly lives up to its moniker.