The 9.51-carat Mellon Blue fetched CHF 20.5 million ($25.6 million) at Christie’s Magnificent Jewels in Geneva on Tuesday — some 20% less than the last time the diamond went under the hammer in 2014.

The sale was evidence of “the elite appetite among collectors for extraordinary and storied gems,” said Rahul Kadakia, president of Christie’s Asia Pacific and chairman of the company’s global luxury group, in a statement the same day.

The modified pear brilliant-cut, fancy-vivid-blue, VVS1-clarity diamond — which has the potential to be internally flawless — previously belonged to American horticulturalist, philanthropist, and art collector Rachel Lambert Mellon, better known as Bunny Mellon, who died in 2014.

The final price was within the auction house’s estimate of $20 million to $30 million and translates to $2.7 million per carat. Christie’s sold it set in a swirling platinum ring with single-cut diamonds.

However, the sale achieved a lower figure than Sotheby’s got for the diamond in New York in November 2014, when a Hong Kong buyer won the piece — then mounted as a pendant — for $32.6 million.

The regression was “shaped heavily by the broader market mood,” said Tobias Kormind, managing director of European online jeweler 77 Diamonds. “Geopolitical tensions — from the war in Ukraine to [US President Donald] Trump’s tariffs — and a weakened Chinese economy that kept many usual buyers away, left the room distinctly cautious.”

Still, $25.6 million was the third-highest price for any vivid-blue diamond sold at Christie’s, the auction house noted. The 14.62-carat Oppenheimer Blue holds the record after realizing $57.5 million in Geneva in 2016, while the 17.61-carat Bleu Royal went for $39.5 million in the same Swiss city in 2023.

Tuesday’s Magnificent Jewels auction, part of Geneva Luxury Week at Christie’s, brought in a combined CHF 60.6 million ($75.6 million), with 95% of items by value finding buyers and 94% by number of lots.

A colored diamond and sapphire ring by designer JAR sold for CHF 2.5 million ($3.1 million), while a late-19th century ruby and diamond star brooch, which can also be worn as a pendant, garnered CHF 2.3 million ($2.8 million). Meanwhile, the “rainbow collection” of 300 unmounted diamonds weighing 0.24 to 4.89 carats scored CHF 1.8 million ($2.2 million).