Rare 11.15-carat 'Williamson Pink Star' diamond set to break records at Sotheby's Hong Kong

As Sotheby's Hong Kong unveiled its schedule for the Autumn Auctions next month, all eyes are on an exceptionally rare pink diamond – Willliamson Pink Star.

At 11.15 carats, Williamson Pink Star is the second largest internally flawless Fancy Vivid pink diamond to ever appear at auction – outsized only by the 59.60-carat CTF Pink Star, which fetched a record-breaking HK$553 million in 2017.

Following recent closure of the Argyle mine, prices for top-quality large pink diamonds has surged over the past decade. Williamson Pink Star is expected to fetch over HK$170 million during a single-lot auction, which has the potential to set a new per carat price record for a Fancy Vivid pink diamond.

The Williamson Pink Star
11.15-carat Fancy Vivid Pink diamond, internally flawless
Expected to fetch more than HK$170,000,000
Auction House: Sotheby's Hong Kong
Sale Date: 5 October 2022


Called ‘Williamson Pink Star’, it is named in homage to two legendary pink diamonds. The first is the celebrated ‘Williamson’ stone –  a pink diamond presented as a wedding gift to Her Majesty Queen Elizabeth II in 1947 by the Canadian geologist Dr. John Thorburn Williamson.

One of the Queen’s favourites, the pink stone originated in the Williamson mine in Mwadui, Tanzania, which was established and once owned by its namesake Dr. Williamson. Having started operation in 1940, it was one of the oldest diamond mines in the world, reputed for producing fine ‘bubblegum’ pink diamonds.

The Williamson stone was refined from a rough stone of 54.50 carats into a 23.60-carat round brilliant-cut diamond. When the polishing was complete, the pink diamond was mounted as the centerpiece of a floral brooch designed by Cartier. Since then, the Queen has worn it on many occasions of her reign, including the Silver Jubilee.

Also yielded at the same mine, the Williamson Pink Star was crafted and polished from a 32-carat rough diamond into a cushion-cut by the master craftsmen at Diacore, bringing out the diamond’s innermost beauty to full display.

Williamson stone served as the centerpiece of Queen Elizabeth II's brooch

Williamson Pink Star was crafted into a cushion-cut diamond

The second is the record-smashing CTF Pink Star mentioned above. The giant 59.60-carat pink diamond, also cut by Diacore, was sold at Sotheby’s Hong Kong for HK$553 million (US$71.2 million) in 2017 to Chow Tai Fook, a renowned Hong Kong-based retail jewellery chain. Up to the present, it still holds the world auction record for any diamond, gemstone or jewel.

Pink is one of the rarest colours to occur naturally in diamonds. Of all the diamonds submitted to the GIA, less than 3% are classified as coloured diamonds, and less than 5% of those are considered predominantly pink. In 2002, GIA conducted a data analysis on over 1,400 pink diamonds – and only 4% of them could reach the grade of Fancy Vivid Pink, most of which are often small in size.

Across auction history, Williamson Pink Star is the second internally flawless Fancy Vivid pink diamond weighing over 10 carats to ever go under the hammer – the first being the CTF Pink Star. 

Not only has the present lot received the highest colour and clarity grades, it is also a Type IIa diamond – the highest level in terms of chemical impurities, where only less than 2% of all gem diamonds falls into this classification. 

CTF Pink Star | Sold at HK$553,037,500 in 2017

CTF Pink Star weighs 59.60 carats

18.96-carat Winston Pink Legacy | Sold at CHF 50,375,000 in 2018

Currently, the record for pink diamond per carat belongs to Winston Pink Legacy.

In 2018, Winston Pink Legacy was acquired by famous American luxury jeweler Harry Winston at CHF 50.4 million (around US$50.66 million) in Geneva. Weighing 18.96 carats, it is valued at HK$20.6 million per carat – meaning Williamson Pink Star would have to fetch at least HK$230 million in order to renew the auction record.