The world’s largest fancy intense blue diamond – the ‘Cullinan Dream’ – to go under the hammer could fetch up to $29m (£19.8m).
The 21.18ct diamond will be auctioned as the centrepiece of Christie’s Magnificent Jewels and The Cullinan Dream auction on 9 June 2016 in New York, with the piece valued at $23m (£15.7m) to $29m (£19.8m).
The other three diamonds cut from the rough include a cushion-cut diamond of approximately 7cts, a radiant-cut diamond of around 10.30cts and a 11.30ct pear-shaped diamond.
Petra Diamonds will receive a 15% share in the Cullinan Dream sales proceeds after expenses.
The diamond, named for its “captivating and celestial beauty”, has been graded by the Gemological Institute of America (GIA) as a fancy intense blue diamond and classified as Type IIb, an extremely rare type which accounts for less than 0.5% of all diamonds found in nature.