Yes, at 15.1 carats, it’s massive. And it’s beautiful. That’s obvious. Blue diamonds are among some of the rarest colored diamonds in the world, as very few mines in the world produce them. But what, exactly, makes the De Beers Cullinan Blue diamond so much more exceptional and rare than all of the other blue diamonds out there? Besides being the largest ever to go to auction (the runner-up is a 14.62 carat stone that sold for $57.5 million nearly seven years ago), its real differentiators go beyond what meets the naked eye.
For one, it’s completely flawless—and we mean that literally. According to the Gemological Institute of America (GIA), it’s the most significant internally flawless step-cut vivid blue diamond the organization has ever graded. And, as a fancy vivid blue, it received the highest possible grading, awarded to less than 1% of blue diamonds submitted for GIA review.
The piece also boasts a classic step cut popular among white diamonds but even more covetable in unusual colors. A GIA monograph explains how “achieving a fancy vivid color grade in a step cut or emerald cut adds to the rarity, since most other fancy shapes intensify the body color more efficiently in the face-up position than step cuts. To achieve a fancy vivid grade with a step cut or emerald cut, the inherent body color has to be stronger than virtually every other fancy shape.” De Beers worked with Diacore, its partner in masterful diamond-cutting, to cut and polish the rough diamond after retrieving it in 2021 from the Cullinan mine in South Africa (one of the only sources of blue diamonds worldwide).
Beyond the actual piece, the De Beers Cullinan Blue represents a moment in history. Important blue diamonds at Sotheby’s are few and far between—it wasn’t until 2007 that a 6.04 ct. flawless emerald-cut fancy vivid blue diamond sold for a record price, raising the minimum to $1 million per carat for these types of diamonds. And since, blue diamonds have sold for astonishing figures ($32.6 million for 9.75 carats in 2014; $48.5 million for 12.03 carats in 2015) but none yet of this size and caliber.
The De Beers Cullinan Blue is estimated to sell for at least $48 million during the Sotheby’s Hong Kong auction on April 27.
(Photos courtesy of Sotheby’s)
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