The second largest internally flawless fancy vivid pink diamond to ever appear at auction was unveiled Wednesday in London by Sotheby’s. The 11.15-carat Williamson Pink Star will be sold in a single-lot auction in Hong Kong on October 5. Its estimate is $21 million.

The auction house says it has the potential to set a new per carat price record for a fancy vivid pink diamond.

“We do have the confidence that it will find a great collector and have the interest of multiple parties,” Wenhao Yu, chairman of Jewellery and Watches at Sotheby’s Asia, told Forbes on Tuesday. “It has the potential to reach a very strong price.”

He adds, “This diamond truly checks all the boxes. It has the best qualities you can have in a pink diamond.”

The current price per carat auction record for a fancy vivid pink diamond is $2,656,909 for the 18.96-carat Winston Pink Legacy, sold in 2018 by Christie’s Geneva. The largest internally flawless, fancy vivid pink diamond offered at auction is the 59.60-carat CTF Pink Star. It was sold by Sotheby’s Hong Kong in 2017 for $71.2 million, a world record for any gem or jewel sold at auction.

Yu compares the Williamson Pink Star to an exceptional work of art.

“We timed this lot to be offered between Sotheby’s modern and contemporary art auctions. That’s because instead of offering just another important diamond, we view this diamond as a work of art from mother earth and a wonder of nature,” Yu says. “It’s comparable to a Monet or a Picasso and is even more rare.”

The Williamson mine is one of the oldest operating diamond mines in the world, famous for producing what is described as “bubblegum” pink diamonds, according to the auction house. One of the best-known diamonds from the mine is the 23.6-carat Williamson Pink Diamond fashioned into a brooch by Cartier and owned by Queen Elizabeth II.

“We wanted to relate the important provenance of the Williamson mine when naming the diamond,” Yu says. “The unique saturated pink color is one of the important qualities of diamonds from this mine. It is an honor for us that after so many decades another important pink diamond comes from the Williamson mine and we can offer it at auction.”

The cushion-shaped diamond was crafted from a 32.32-carat rough diamond by Diacore, a diamond manufacturer that specializes in crafting rare, exceptional fancy-colored diamonds. The company purchased the gem in late 2021 for $13.8 million. Yu says crafting the diamond is just as important as discovering it, and Diacore is one of the few companies in the world capable of cutting and polishing such an important gem.

“Not every rough can yield a diamond of this high quality so we should also give credit to Diacore,” he says. “They really made cutting and polishing into an art. They are very skilled and experienced with the best technology and a lot of courage. It’s rare to have a vivid pink color. It’s rarer when it’s over 10 carats and even more rare if it’s internally flawless. It’s luck to find this kind of diamond that was formed underground for millions of years, and it takes a great amount of art and creativity to fashion it into a gorgeous stone with so many exceptional qualities.”

Pink diamonds are among the rarest colors to occur naturally in diamonds. Of all the diamonds submitted to the Gemological Institute of America (which analyzes and grades diamonds), fewer than 3% are classified as colored diamonds, and fewer than 5% of those are considered predominantly pink.

The Argyle Mine in Australia, before it was retired in 2020 after exhausting its supply of gem-quality diamonds, produced more than 90% of the world’s pink diamonds. The absence of pink diamonds from this mine makes important pink diamonds like the one being offered even more rare, Yu says.

“Pink diamonds are still growing in demand in the market, and this now makes the Williamson Pink Star even more sought after,” he says.

The diamond is being presented in an 18k gold ring flanked by trapeze-cut diamonds and embellished with brilliant-cut diamonds.

London is the first stop where the diamond will be viewed by the public. It will then travel to Dubai, Singapore and Taipei before the final viewing and sale in Hong Kong.