Christie's jewelry department head Rahul Kadakia gestures during the sale of The Pink Legacy, a 18.96 carat fancy vivid pink diamond once owned by the Oppenheimer family, Nov. 13, 2018, in Geneva ...

The world’s largest fancy intense pink diamond could sell for up to $30 million at a Sotheby’s auction on Nov. 15.

Failing to sell was the 37.30-carat “Raj Pink,” the world’s largest known fancy intense pink diamond. It has an estimate of $20 million - $30 million.

In 2017, Christie’s Hong Kong sold The Pink Promise, an oval-shaped, 14.93-carat fancy vivid pink diamond, for HK$250 million (US$32.5 million, or US$2.2 million per carat).

A fancy vivid pink diamond of more than 10 carats is extremely rare. The single-lot sale, orchestrated by Sotheby’s Auction House in New York, is set for Oct. 5 in Hong Kong. Traveling ...

This fancy vivid purple pink diamond is of an unprecedented size of 15.81 carats, which is the largest of its kind (Fancy Vivid Purple Pink) to be offered at any auction, the auction house said.

A fancy vivid pink 14.83-carat diamond is expected to fetch between CHF21 million and CHF35 million (US$23 million and US$38 million) at an upcoming Sotheby’s live auction in Geneva.