In Geneva yesterday, one of the world’s most storied blue diamonds once again took center stage at a high-profile auction. “The Mellon Blue,” a 9.51-carat Fancy Vivid Blue, Internally Flawless diamond with an elite pedigree, sold for 20.525 million Swiss francs ($25.6 million) at Christie’s Magnificent Jewels auction. The price fell squarely within the house’s pre-sale estimate of $20–30 million — even as a noticeably cautious mood settled over the bidding room.
Mounted in a graceful, serpentine ring, The Mellon Blue is a peerless example of natural rarity. Its color —an intense, boron-infused azure formed deep within the Earth’s mantle — is certified by the Gemological Institute of America as Fancy Vivid Blue, the highest grade for hue saturation.
The diamond’s impressive size, flawless clarity and elegant pear shape elevate it into the uppermost tier of collectible gems, joining the company of other blue-diamond legends, such as the 15.10-carat “De Beers Cullinan Blue” ($57.5 million, Sotheby’s Hong Kong, 2022), the 14.6-carat “Oppenheimer Blue” ($57.5 million, Christie’s Geneva, 2016) and the 12.03-carat “Blue Moon of Josephine” ($48.5 million, Sotheby’s Geneva, 2015).
The diamond owes much of its fame to its former owner, Rachel “Bunny” Mellon (1910–2014), the American philanthropist, horticulturalist and cultural tastemaker whose refined sense of beauty left an indelible mark on both art and landscape design. A close friend of former first lady Jacqueline Kennedy, Mellon famously redesigned the White House Rose Garden in the early 1960s. Her taste in jewelry mirrored her aesthetic sensibilities: discreet, elegant and quietly opulent. The Mellon Blue, originally worn as a pendant, was among her most treasured possessions and came to symbolize her understated sophistication.
When the diamond last appeared at auction in 2014, the mood was electric. That sale at Sotheby's New York, held shortly after Mellon’s passing, sparked a 20-minute bidding war, ultimately driving the price to $32.6 million, more than double its high estimate — a record at the time for a blue diamond. Yesterday’s scene in Geneva, by contrast, unfolded in a more measured rhythm. Bidders in the room and on the phones responded more deliberately, reflecting what several observers described as “a cautious atmosphere.”
Industry analysts attributed the restraint to a confluence of global factors — geopolitical tensions, including the war in Ukraine, renewed US tariffs, as well as a slowdown in the Chinese economy, which kept some traditional high-end buyers sidelined. One jewelry-industry insider who attended the Geneva auction summed it up succinctly: “Not the dazzling moment I expected… the room was distinctly cautious.”
Even so, Christie’s hailed the sale as a triumph of connoisseurship. “It was another notable moment for Christie’s Luxury,” said Rahul Kadakia, the auction house’s chairman of global luxury. “The Mellon Blue remains one of the most exquisite and storied gems ever to appear at auction.”
Credits: Images courtesy of Christie’s.