‘Mellon Blue’ diamond sells for US$26.6 million at Swiss auction

A Christie's employee displays the Mellon Blue, a fancy vivid blue pear-shaped diamond of 9.51 carats, during a preview at Christie's in Geneva, Switzerland, Friday, Nov. 7, 2025, ahead of an auction where it is estimated to sell for between 20 and 30 million US dollars. (Martial Trezzini/Keystone via AP)

GENEVA — A blue diamond weighing nearly 10 carats has sold at auction in Switzerland for 20.5 million Swiss francs ($25.6 million) including fees.

The pear-shaped 9.51-carat “Mellon Blue” -- named for the late American arts patron Rachel “Bunny” Mellon -- had been expected to fetch $20-$30 million at the Christie’s auction on Tuesday.

The house said the stone came in on the estimated range. The final price includes the “buyer’s premium” and other fees.

“Not the dazzling moment I expected,” said Tobias Kormind, managing director of online jeweler 77 Diamonds. He said the gem was “tipped as the season’s headline act” but was weighed down by a broader market mood.

“Geopolitical tensions -- from the war in Ukraine to Trump’s tariffs -- and a weakened Chinese economy that kept many usual buyers away, left the room distinctly cautious,” he said in a statement.

Auctioneer Rahul Kadakia, chairman of the global luxury group at Christie’s, hailed a “notable moment” for his team, “evidencing the elite appetite among collectors for extraordinary and storied gems.”

It was a far cry from the peak sale for 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 more than $57 million.

The Mellon Blue was previously sold in 2014, the year that Mellon died, for $32.6 million, which was one of the highest prices ever paid for a colored diamond at auction, Christie’s says.

For decades, the stone was part of Mellon’s private collection.

Max Fawcett, Christie’s global head of jewelry, said the Mellon Blue was unlike the vast majority of other modern gems that have had facets added and been modified to enhance the color.

“When you have great shape and great color, you’re looking at the gem of gems,” he said Friday, noting the stone’s grade of Fancy Vivid Blue and Internally Flawless by the Gemological Institute of America. “That’s what this is.”

The auction was the first installment of two days of jewelry auctions in Geneva. On Wednesday, rival Sotheby’s is putting up the “Glowing Rose” pink diamond that’s expected to draw bids of around $20 million.

The Associated Press