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The second largest and purest pink diamond ever to appear at auction is expected to achieve more than HK$170 million (US$21 million) this October at Sotheby’s in Hong Kong.

The 11.15-carat diamond, internally flawless in fancy vivid pink color, is only outsized by the CTF Pink Star, a 59.60-carat oval diamond that sold for a record US$71.2 million in April 2017 at Sotheby’s, the auction house said.

Dubbed The Williamson Pink Star, this cushion-shaped stone has been named in homage to the CTF Pink Star and the “Williamson” stone, a 23.60-carat diamond given as a wedding present to Queen
Elizabeth II
in 1947 by
John Thorburn Williamson,
who owned the Williamson mine in Mwadui, Tanzania, where it was discovered, according to
Wenhao Yu,
chairman of jewelry and watches at Sotheby’s Asia.

The Williamson Pink Star was discovered last year and was cut and polished by New York-based Diacore, who was also responsible for manufacturing the CTF Pink Star into its final form, Yu says.

“The stone is a perfect combination of natural wonders with human craftsmanship and technology,” he says.

A pink diamond is one of the rarest diamonds. Of all the diamonds submitted to the Gemological Institute of America for grading, less than 3% are classified as colored diamonds, and less than 5% of those are considered predominantly pink. 

“This fancy vivid pink diamond, weighing over 10 carats, is therefore of the utmost rarity,” Yu says. “Its beauty, rarity and durability makes it a truly museum-quality gem.”

The Williamson Pink Star will be unveiled Wednesday at Sotheby’s in London. It will be on a touring exhibition with stops in Dubai, Singapore, Taipei and Hong Kong, where it will be offered in a single-lot auction on Oct. 5.