The Mellon Blue Diamond to Auction at Christie’s Geneva With $20–30 Million Estimate

October 3, 2025

© Christie’s Auction House

The Mellon Blue Diamond, a 9.51-carat Fancy Vivid Blue of extraordinary purity and provenance, is set to headline Christie’s Geneva Magnificent Jewels auction on November 11, 2025. With an estimate between $20 million and $30 million, it is poised to become one of the most significant blue diamonds ever to appear at auction.

Originally part of the legendary collection of Rachel Lambert “Bunny” Mellon — a philanthropist, art collector, and confidante of Jacqueline Kennedy — the diamond has been admired for both its exquisite color and timeless design. Its pear shape and vivid hue represent the pinnacle of natural blue diamond grading, a rarity that only a fraction of one percent of diamonds ever achieve.

The diamond’s story begins decades ago, when it was first acquired by the Mellon family, whose taste for exceptional gems and art made their private collection one of America’s most admired. After Mrs. Mellon’s passing, the diamond reemerged as a quietly held treasure before being consigned to Christie’s for its upcoming Geneva sale.

Graded by the Gemological Institute of America (GIA) as Fancy Vivid Blue, VS2 clarity, the Mellon Blue exemplifies the perfect balance of brilliance and color saturation. Experts note that the tone and intensity rival iconic blue diamonds such as the Oppenheimer Blue and the Blue Moon of Josephine, both of which achieved record-breaking results at auction.

Christie’s will showcase the diamond in a global preview tour, with stops in Hong Kong, New York, and London, before the Geneva sale. Collectors and connoisseurs are already anticipating strong bidding activity, given the rarity and pedigree of the stone.

The Mellon Blue Diamond stands as a testament to nature’s artistry and human craftsmanship — a legacy that continues to captivate across generations. Its sale this November will not only mark a milestone for Christie’s but may also set a new benchmark for the market of Fancy Vivid Blue diamonds.

For more information, including full grading details and provenance notes, visit Christie’s official catalogue.