Sotheby’s Geneva is preparing to sell the largest cushion-shaped fancy vivid blue diamond ever to appear at auction.

The rare stone will lead Sotheby’s Magnificent Jewels and Noble Jewels sale scheduled to take place November 11 in Geneva.

It has been said that the 12.03ct diamond named the ‘Blue Moon’ could set a new auction record.


The cushion-shaped, brilliant-cut stone boasts an exceptional clarity, declared internally flawless by the GIA.

It comes to market with an estimate of between $35 million (£22.5 million) and $55 million (£35 million). If it sells at the upper end of that price range, the stone could become the most expensive diamond in auction history.

The current record is held by Graff Pink, a 24.78ct fancy intense which sold for $46.2 million (£16.8 million) at Sotheby’s Geneva in Novemeber 2010.

Scientists from the National Gem and Mineral Collection at the Smithsonian Institution studied the Blue Moon diamond and noted that the colour is “true and saturated” throughout, with no other colours present.

The stone was cut in January from a 29.62ct piece of rough unearthed at Petra Diamond’s Cullinan mine in South Africa. In February Coro International NY purchased it for $25.6 million (16.4 million) – $862,780 (£555,022) per carat.


Photo credit: National Jeweler