15.1-carat Cullinan Blue expected to break record-sale history

The Cullinan Blue, which is expected to fetch more than $US45 million ($AU62.45 million), is believed to be the largest and one of the only five blue diamonds in excess of 10 carats to be auctioned.

“This diamond ranks as one of the best De Beers has ever seen. 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”.

Bruce Cleaver, De Beers

The diamond will be the solo centrepiece of Sotheby’s Hong Kong Luxury Week. It has been classified by the Gemological Institute of America (GIA) as internally flawless type IIb, its highest colour grading category, to date.

According to Bruce Cleaver, CEO, De Beers group “This diamond ranks as one of the best De Beers has ever seen. 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”. 

Discovered in April 2021 at the Cullinan Mines in South Africa by UK-based Petra Diamonds, the diamond was part of the special tender purchased by De Beers and diamond manufacturing firm Diacore for $US40.2 million ($AU55.79 million).

The step-cut stone was taken from a 39.35-carat rough blue diamond sold by Petra to DeBeers and Diacore three months after it was unearthed, then cut and polished into the Cullinan Blue.

Since then, the diamond has been showcased in exhibitions in New York, London, Dubai, China, and Taiwan.

Record-breaking expectations

Sotheby's Record-breaking Blues

2014 – The Zoe Diamond Sold for US$32.6 million in New York • Shape: Pear-shaped • Carats: 9.75-carats • Colour: Fancy Vivid Blue • Sold Date: November 2014

2015 – The Blue Moon of Josephine Sold for US$ 48.46 million in Geneva • Shape: Cushion-shaped • Carats: 12.03-carats • Colour: Fancy Vivid Blue • Internally Flawless • Sold Date: November 2015

2016 – The Millennium Blue Sold for US$31.83 million in Hong KOng • Shape: Oval-shaped • Carats: 10.10-carats • Colour: Fancy Vivid Blue • Internally Flawless • Sold Date: April 2016

2016 – The Sky Blue Diamond Sold for US$17 million in Geneva • Shape: Emerald-shaped • Carats: 8.01-carats • Colour: Fancy Vivid Blue • Sold Date: November 2016

2017 – The Memory of Autumn Leaves Sold for US$42 million in Geneva • Shape: Pear-shaped • Carats: 14.54-carats • Colour: Fancy Vivid Blue • Internally Flawless • Sold Date: May 2017

Industry expectations are high for the auction with predictions that the rare blue will be sold for in excess of $US50-60 million ($AU69.39-83.26 million).

It is larger than the 14.62-carat Oppenheimer Blue sold by Christie’s-Geneva in May 2016 for $US57.5 million ($AU79.79 million) and the 12.03-carat Blue Moon in 2015 auctioned by Sotheby’s for $US48.5 million ($AU67.31 million).

The Oppenheimer Blue currently holds the record for the largest blue diamond sold in auction.

On the other hand, the Blue Moon currently holds the record for being the most expensive blue diamond in terms of carat value which is more than $US4 million ($AU 5.55 million) per carat.

The Blue Moon was purchased from Sotheby’s by the Hong Kong billionaire and renamed the Blue Moon of Josephine, in honour of the new owner’s young daughter.

The largest blue diamond to date is the 20.46-carat Okavango Blue Diamond, which is said to be one of the most fascinating and rarest colour diamonds in existence.

Currently on display at the American Museum of Natural History, the stone is about the size of a plump almond and traces its origins back millions of years and from hundreds of kilometres underneath the earth’s surface.

The oval-shaped stone - unearthed in 2018 from Botswana’s Orapa Mine located in the lush Okavango Delta - was given a clarity grade of VVS1 for its near-perfect condition and was cut from a 41.11-carat rough diamond.

Unlike most diamonds that were created around 160 to 240 kilometres below the surface, Okavango Blue may have formed for millions of years at the transition zone - around 640 kilometers down - through a geological process called subduction.

In line with the rising popularity of blue diamonds, Kunming Diamonds purchased the entire collection of blue and violet Argyle diamonds at the final 2021 October Argyle tender totalling 24.88-carats and aptly titled 'Once in a Blue Moon'. 

Discovered in April 2021 at the Cullinan Mines in South Africa by UK-based Petra Diamonds, the diamond was part of the special tender purchased by De Beers and diamond manufacturing firm Diacore for $US40.2 million ($AU55.79 million). Source: Sotheby's

The step-cut stone was taken from a 39.35-carat rough blue diamond sold by Petra to DeBeers and Diacore three months after it was unearthed, then cut and polished into the Cullinan Blue. Source: Sotheby's

The Cullinan Blue was originally a 39.34-carat Type IIb rough recovered from the South African Cullinan diamond mine in April 2021 Source: Petra Diamonds

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