FLOAT 100 · Jewelry · No. 2
The De Beers Blue (Cullinan Blue)
A 39-carat blue crystal that probably formed far deeper in the Earth than ordinary diamonds was pulled from a South African mine in April 2021, cut to 15.10 flawless carats, and sold a year later after eight minutes of bidding for about $57.5 million.
- Year
- sold 2022
- By price in jewelry
- 4 of 100
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- The De Beers Cullinan Blue
- Weight
- 15.10 carats
- Grade
- Fancy Vivid blue, Internally Flawless, graded by the Gemological Institute of America with a special monograph report
- Cut
- Cut-cornered rectangular step cut, 17.47 x 11.53 x 7.94 mm
- Type
- Type IIb, colored blue by boron
- Rough
- 39.34 carats (some reports say 39.35), recovered in April 2021 at Petra Diamonds' Cullinan mine, South Africa
- Cutter
- Diacore, which bought the rough jointly with De Beers
- Sold
- April 27, 2022, in Hong Kong, for HK$450.9 million, reported as $57,471,960, to an anonymous telephone bidder
- Distinction
- The largest internally flawless step-cut vivid blue diamond the GIA had graded, and the largest vivid blue ever offered at auction
Out of the only big blue mine
The stone came from the Cullinan mine, established in 1902 as the Premier mine near the town of Cullinan, about 40 kilometers east of Pretoria. It is famous for the Cullinan Diamond, a 3,106.75-carat rough found there by surface manager Frederick Wells on January 25, 1905, still the largest gem-quality rough diamond ever found. The mine was renamed Cullinan in November 2003 for its centenary, and a consortium led by Petra Diamonds completed its purchase of the mine from De Beers on July 16, 2008. It is described as the only significant source of blue diamonds in the world.
In April 2021 Petra recovered a 39.34-carat type IIb blue crystal that it called exceptional in both color and clarity. Reports of the rough weight differ by a hundredth of a carat: the GIA's study and trade reports give 39.34 carats, while other reports give 39.35. Petra first said it expected to sell the stone through a special tender.
Blue had been good business for Petra at Cullinan. The mine's earlier blue finds included a 29.62-carat rough recovered in January 2014 that became the Blue Moon of Josephine, and in November 2020 Petra sold five blue diamonds totaling 85.62 carats, called the Letlapa Tala collection, for $40.36 million to the same buyers who would take the 2021 stone.
The buyers and the cutter
In July 2021, instead of a tender, Petra sold the rough directly to a partnership of De Beers Group and the diamond manufacturer Diacore, splitting the stone equally between them. The price was reported as $40.2 million, or about $1 million a carat; one report gives $40.18 million and another $40.1 million. Petra's chief executive, Richard Duffy, said it was the highest price the company had ever achieved for a single stone.
'It is a privilege to have the opportunity to work with such a miracle of nature,' said Paul Rowley, De Beers' executive vice president of diamond trading, calling it a delight 'to see the legendary Cullinan deposit producing yet another breathtakingly beautiful gemstone.' Diacore's executive chairman, Nir Livnat, said the company was 'excited and humbled' to shape 'one of the most special and rare blue diamonds of such size and color.'
Diacore cut and polished the crystal into its final form. The cutters chose a step cut, a long rectangular style with clipped corners. As the GIA notes, a step cut does not enhance color the way other faceting styles do, so the vivid blue grade owes nothing to tricks of the cut. Less than 40 percent of the rough's weight survived into the finished 15.10 carats.
What the lab saw
The GIA graded the stone Fancy Vivid blue and gave it a special monograph report. Under the microscope it found no inclusions or graining, so the clarity grade was Internally Flawless, and the blue color was spread evenly through the stone. The GIA described it as the largest internally flawless step-cut vivid blue diamond it had ever graded.
Its color comes from boron. Infrared measurements showed about 0.33 parts per million of uncompensated boron, inside the typical range for natural type IIb diamonds, close to the Hope diamond's roughly 0.36 ppm and higher than the Wittelsbach-Graff's roughly 0.19 ppm. Natural type IIb blue diamonds over 10 carats, the GIA wrote, are extremely rare.
It also behaves differently from those famous blues. The Hope and the Wittelsbach-Graff, both mined in India's Golconda region, glow a strong, lasting red after short-wave ultraviolet light; the Cullinan stone showed no fluorescence or phosphorescence under conventional UV lamps, and only a weak aqua-blue glow and faint pinkish red afterglow under very strong short-wave UV. Its strain pattern suggested a much less distorted crystal lattice than either.
The GIA concluded that its features suggest it is a superdeep diamond, one of the blue diamonds whose boron, 2018 research showed, came from pieces of the Earth's crust that sank to the extreme depths where these diamonds form. In the lab's words, it 'will remain one of the world's most important diamonds.'
Eight cities, eight minutes
Ahead of the sale the stone was announced as the centerpiece of a Hong Kong luxury week, offered in a stand-alone, single-lot live auction with an estimate of up to $48 million. Before the sale it was shown in New York, London, Dubai, Singapore, Shanghai, Beijing, Shenzhen and Taipei. De Beers reported that only five blue diamonds over 10 carats had ever come to auction, and none over 15 carats.
'This diamond ranks as one of the best De Beers has ever seen,' said De Beers chief executive Bruce Cleaver. The auction house's Asia chair, Patti Wong, called it 'truly a once-in-a-generation stone.'
On April 27, 2022, in Hong Kong, four bidders competed for eight minutes before the stone sold to an anonymous client bidding by telephone for HK$450.9 million, reported as $57,471,960 and widely rounded to $57.5 million. That was well above the high estimate.
Where it sits among the great blues
The sale placed the stone among the most expensive diamonds ever sold at auction, reported as the third most valuable of any color. Above it were the CTF Pink Star, sold in 2017 for $71,175,926, and the 14.62-carat Oppenheimer Blue, sold in Geneva in May 2016 for $57,541,779, just $69,819 more. The auction house called the two prices a near tie, and one trade report said the Cullinan stone tied the record for a blue diamond at auction.
Among the vivid blues it outweighs the earlier stars: the 12.03-carat Blue Moon of Josephine, also from Cullinan, sold for $48.5 million in 2015, and the 14.54-carat Apollo for $42.1 million in 2017. Its combination of vivid color, a color-neutral step cut, more than 15 carats and an internally flawless grade is what the GIA called exceptionally rare.
The buyer has not been named, and no later sale of the stone has been reported.
The numbers
- Carat weight
- 15.10 ct (from 39.34 ct rough)
- Color and clarity
- Fancy Vivid blue, Internally Flawless
- Measurements
- 17.47 x 11.53 x 7.94 mm, cut-cornered rectangular step cut
- Type
- IIb, about 0.33 ppm uncompensated boron
- Origin mine
- Cullinan (formerly Premier) mine, South Africa, operated by Petra Diamonds
- Cutter
- Diacore
Timeline
The Premier mine is established near Pretoria, South Africa.
Surface manager Frederick Wells finds the 3,106.75-carat Cullinan Diamond at the mine.
The Premier mine is renamed the Cullinan mine for its centenary.
A consortium led by Petra Diamonds completes its purchase of the mine from De Beers.
A 29.62-carat blue rough is recovered at Cullinan; it becomes the Blue Moon of Josephine.
Petra sells five blue diamonds, the Letlapa Tala collection, to De Beers and Diacore for $40.36 million.
Petra recovers the 39.34-carat type IIb blue rough at Cullinan.
De Beers and Diacore buy the rough jointly for about $40.2 million, Petra's highest price for a single stone.
The cut 15.10-carat stone is graded by the GIA and announced for a single-lot auction.
The stone tours New York, London, Dubai, Singapore, Shanghai, Beijing, Shenzhen and Taipei.
It sells in Hong Kong for HK$450.9 million, about $57.5 million, after eight minutes of bidding.
The GIA publishes its study of the stone in the Summer 2022 issue of Gems & Gemology.
The world in 2016
The 14.62-carat Oppenheimer Blue sells at auction in Geneva.
The CTF Pink Star sells for about $71.2 million, the auction record for any diamond.
The Winter Olympics open in Beijing.
Russia launches a full-scale invasion of Ukraine.
The EU and US move to cut Russian banks off from the SWIFT payment system.
Yoon Suk-yeol wins South Korea's presidential election.
China Eastern Airlines Flight 5735 crashes, killing all 133 aboard.
Price record
| Date | Price | Kind |
|---|---|---|
| Jul 2021 | $40,200,000 | Private saleThe 39.34-carat rough, bought directly from the miner by De Beers and Diacore in equal shares; also reported as $40.18 million and $40.1 million. About $1 million per carat. |
| Apr 27, 2022 | $48,000,000 | Estimate, not a saleHigh pre-sale estimate for the polished 15.10-carat stone. |
| Apr 27, 2022 | $57,471,960 | Sold at auctionSold in Hong Kong for HK$450.9 million to an anonymous telephone bidder after eight minutes and four bidders. |
A realized auction price is what a buyer actually paid on the date shown, including the buyer's premium where the sale reported it. It is the strongest kind of reference price, and it is a record of one sale of one object on one day, not a promise of what the next example will bring.
By reference price, The De Beers Blue (Cullinan Blue) is number 4 of 100 in the jewelry entries of the FLOAT 100. 44 of those 100 rest on a realized sale; the rest carry an asking price or a guide value, and each page says which. Rank within the FLOAT 100 itself (2 here) is editorial: how much an object defines its field, not price alone.
Did you know
- The rough cost about $1 million per carat before it was cut.
- Less than 40 percent of the rough's weight made it into the finished stone.
- Unlike the Hope diamond, it does not glow red after ultraviolet light.
- Its boron level is almost the same as the Hope diamond's.
- Blue type IIb diamonds conduct electricity, unusual for a diamond.
- Before it, no blue diamond over 15 carats had ever come to auction.
- The whole auction took eight minutes.
How this page is made
- The figure
- One reference price, shown with its own kind. FLOAT does not average it with anything or adjust it for time.
- Realized or not
- A realized price is a completed sale. An asking price, an estimate and a price-guide value are not sales, and are labeled as such wherever they appear.
- The story
- Researched from published records and checked fact by fact. Updated Oct 1, 2026.
- Archive
- Oct 5, 2026