A spectacular 9.51-carat Fancy Vivid Blue diamond known as the “Mellon Blue” has sold for $25.5 million (CHF 20.5 million) at Christie’s Magnificent Jewels auction in Geneva on November 11, 2025. The sale, which fell within the pre-auction estimate of $20–30 million, attracted significant attention from collectors worldwide despite a cautious market climate.
The pear-shaped gemstone, graded as Internally Flawless and recently set in a platinum ring with single-cut diamonds, once belonged to Rachel Lambert “Bunny” Mellon, the renowned American horticulturalist, philanthropist, and art collector who passed away in 2014. The stone’s exceptional Fancy Vivid Blue classification places it in an extraordinarily rare category, accounting for less than one percent of all blue diamonds—gems that already comprise less than 0.1 percent of all diamonds worldwide.
The diamond commanded considerable bidding interest during the auction, though the final price represented a decline from its previous market appearance. When the Mellon Blue was last offered at Sotheby’s in New York in November 2014, it achieved $32.6 million, establishing a world record for a blue diamond at that time. The 2025 sale reflects approximately a 22 percent decrease from that 2014 price, or nearly 60 percent less when adjusted for inflation.
Despite the price decline, the sale underscores the enduring appeal of historically significant colored diamonds. “This result evidences the elite appetite among collectors for extraordinary and storied gems,” stated Rahul Kadakia, Christie’s International Head of Jewellery, in a statement following the auction. Max Fawcett, Christie’s global head of jewelry, highlighted the stone’s singular appeal, noting that its combination of remarkable shape and color remains exceptionally uncommon.
The Mellon Blue ranks among the most valuable blue diamonds ever sold, though it remains surpassed by the 14.62-carat Oppenheimer Blue, which fetched $57.5 million at Christie’s Geneva in 2016, and the 15.10-carat De Beers Cullinan Blue, which sold for the same amount at Sotheby’s in 2022. The winning bidder was reported to be a collector from Hong Kong, continuing a long-established tradition of Asian collectors acquiring exceptional blue diamonds.
Athmaja Biju is the Editor at Abir Pothi. She is a Translator and Writer working on Visual Culture.
