A 15.10-carat fancy vivid blue diamond, known in the trade as the De Beers Cullinan Blue, is expected to sell for more than HK$380 million (around US$48 million) at Sotheby’s Hong Kong. 

Cut from a historical rough stone discovered in April 2021, the gem has re-emerged as the largest vivid blue diamond ever to appear at auction and the largest internally flawless step-cut vivid blue diamond that the Gemological Institute of America has ever graded. 

Blue diamonds of this importance are exceptionally rare, with only five 10-carat+ examples ever having come to auction. None of which have exceeded 15 carats, making the appearance of this flawless gem a landmark event in itself, according to Sotheby’s.

The De Beers Cullinan Blue anchors Sotheby’s Hong Kong Luxury Week, and will be offered in a stand-alone, single-lot live auction in late April 2022. Sotheby’s will announce the exact date later.

Patti Wong, chairman of Sotheby’s Asia, called the Cullinan Blue “the rarest of the rare” and “the ultimate masterpiece,” while Wenhao Yu, chairman of Jewellery and Watches at Sotheby’s Asia, described it as bearing the “hues of the sky and sea, perfected through a step-cut that is bold, distinctive and masterful.”

Bruce Cleaver, CEO of De Beers Group, ranked the diamond as “one of the best De Beers has ever seen.” 

The diamond was discovered at the Cullinan Mine in South Africa in 2021, one of very few sources in the world for extremely rare blue diamonds. Over the past year, De Beers has worked with its partner, Diacore, to cut and polish the extraordinary rough diamond and bring The De Beers Cullinan Blue to life.

The exceptional gem will be showcased on a worldwide tour. Currently on view in Sotheby’s galleries in New York, it will then travel to cities including London, Dubai, Singapore, Shanghai, Beijing, Shenzhen and Taipei.