In April 2021, a rare blue diamond was unearthed at the Cullinan Mine in South Africa. This mine is one of the few in the world where blue-coloured diamonds are mined due to the natural addition of boron. To bring out the best in the special stone, it was transformed by the diamond cutters at De Beers into a brilliant 15.10 carat step-cut or emerald-cut gemstone known as The De Beers Cullinan Blue. On 27 April, a year after its discovery, the Cullinan Blue will go under the hammer at Sotheby's in Hong Kong.
"This diamond ranks as one of the best De Beers has ever seen," said Bruce Cleaver, the CEO of De Beers. "It is extremely rare and unique, and as the Home of Diamonds, De Beers is pleased to join together with Sotheby’s to bring this diamond to the world."
See also: The World's 10 Most Expensive Diamonds
See also: Barnebys’ Guide to Diamonds
The Gemological Institute of America (GIA) also took a close look at the blue diamond and stated that it was a specimen of superlatives. Its colour was described as Fancy Vivid Blue, the best possible colour grade. Added to this is its impeccable clarity with a classification as Type IIb, the top level among natural diamonds, which make up just 0.1% of all stones.
The best way to compare the De Beers Cullinan Blue is with the world's most expensive blue diamond, The Oppenheimer Blue, which was sold at Christie's in 2016 for €51.7 million. Also from the Cullinan mine, The Oppenheimer Blue is Fancy Vivid Blue in colour, a Type IIb diamond and has a step cut sparkle. However, the Cullinan Blue edges out the Oppenheimer Blue in terms of weight, as the latter is 'just' 14.62 carats. The Cullinan Blue is therefore poised to dethrone the Oppenheimer as the most expensive blue diamond in history.
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