Blue diamond by sotheby

Photo by Sotheby’s

A 15.1-carat fancy blue vivid diamond will hit Sotheby’s Hong Kong auction block in April with a starting price of USD$48 million, the highest estimate ever for a blue diamond.

The ‘De Beers Cullinan Blue Diamond’ — named for the South African mine where it was discovered in April 2021 — is also the largest fancy vivid blue diamond ever to appear at auction.

“Blue diamonds of any kind are rare on the market, but this is the rarest of the rare; nothing of remotely similar caliber has appeared at auction in recent years,” Sotheby’s Asia chairwoman, Patti Wong, said in a press statement

In fact, Sotheby’s says only five gems over 10 carats have ever appeared at auction, and none have been over 15 carats, “making the appearance of this flawless gem a landmark event in itself.” 

Even the Gemological Institute of America (GIA) considers this diamond one of a kind, calling it “the largest internally flawless step-cut vivid blue diamond” it has ever graded, explaining that just 1% of blue diamonds submitted to the organization are ever even awarded this remarkable color grade of “fancy vivid blue.”

Just like colorless diamonds, colored diamonds are formed naturally out of carbon deep below the surface of the Earth at temperatures greater than 1000 degrees Celsius over the course of millions of years. However, just 0.1% of all diamonds end up with a fluke, altered chemical structure, giving them stunningly rare color. In the case of blue diamonds, boron is trapped inside the rough diamond during formation, creating color that ranges from blue-green to blue-purple with different intensities. 

Most blue diamonds are grey with a tint of blue creating a ‘steely’ color, but as saturation increases, blue diamond ratings go from ‘fancy’ to ‘fancy intense’ and the ultra-rare ‘fancy vivid’ like the ‘De Beers Cullinan Blue Diamond’.

“Hundreds of millions of years in the making, this extraordinary blue diamond is surely one of nature’s finest creations. Now brought to dazzling life by the hand of one of the world’s most skillful cutters, it is the ultimate masterpiece — as rare and desirable as the very greatest works of art,” Wong went on to say.

While colored diamonds are found all over the world, the Cullinan mine in South Africa where it was found is one of the few known to boast blue diamonds. The mine has famously yielded some of the world’s most precious diamonds, like the 3,106 carat ‘Cullen Diamond’ from 1905, and more recently, the De Beers Millennium Jewel 4, a 10.10 carat fancy vivid blue, oval-shaped diamond that sold at Sotheby’s Hong Kong in April 2016 for $31.8 million. 

Today, the mine is owned by Petra Diamonds Ltd., which acquired it from De Beers in 2008.

But as Sotheby’s notes, what also makes this blue diamond exceptional is the cut. Diacore, a leading diamond manufacturer and cutter, was trusted with the step-cut and polishing of the rough diamond over the last year — a style renowned for its use in white diamonds, but highly sought-after in rare colors. 

“…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,” the GIA Monograph explained. 

But achieving the cut is easier said than done. As one of the hardest materials on earth, incredible skill and precision is needed to cut them. “With blue diamonds, the challenge is yet greater: because of their formation, every faceting process of a blue diamond demands extreme care and precision,” Sotheby’s explained in their press statement. “There is zero tolerance for miscalculation; any minute error would result in a loss of color and destruction of the beauty.”

Now, with internally flawless clarity and excellent polish that results in sparkle and high light return, the 15.1-carat fancy blue vivid ‘De Beers Cullinan Blue Diamond’ will hit Sotheby’s auction block at an undisclosed date in April. 

However, before that, the diamond will first travel to London, Dubai, Singapore, Shanghai, Beijing, Shenzhen, and Taipei where it will sit on exhibition before being sold in Hong Kong.