Editor’s Note
A rare 9.51-carat blue diamond, known as the “Mellon Blue,” has sold for 20.5 million Swiss francs ($25.6 million) at auction in Switzerland.

A nearly 10-carat blue diamond was sold at an auction in Switzerland for 20.5 million Swiss francs ($25.6 million), including commissions.
The 9.51-carat pear-shaped “Mellon Blue” — named after the late American arts patron Rachel “Bunny” Mellon — was expected to fetch between $20 and $30 million at Christie’s auction on Tuesday. The auction house stated that the stone sold within the estimated range. The final price includes the “buyer’s premium” and other fees.
He added that the gem was “touted as the biggest of the season” but was affected by a negative market environment.
Auctioneer Rahul Kadakia, president of Christie’s global luxury group, hailed a “remarkable moment” for his team that “evidences the appetite of the elite among collectors for extraordinary and historic gems.”
It was very different from the peak sale of a blue diamond: Christie’s says its highest price for a vivid blue diamond was set in Geneva in 2016 when the 14.62-carat Oppenheimer Blue sold for over $57 million.
The Mellon Blue was previously sold in 2014, the year Mellon died, for $32.6 million, which was one of the highest prices ever paid for a colored diamond at auction, according to Christie’s. For decades, the stone was part of Mellon’s private collection.
Max Fawcett, Christie’s global head of jewelry, noted that the Mellon Blue was different from the vast majority of other modern gems that have had facets added and been modified to enhance color.
The auction was part of the first of two days of jewelry auctions in Geneva.