Christie's auction in November: The Mellon Blue goes under the hammer

On November 11, Christie's auction house will offer a unique blue diamond, the Mellon Blue, in a pear-cut Fancy Vivid Blue color and weighing 9.51 carats, in a live auction. Before its auction, the blue diamond can be admired in Hong Kong and subsequently in Geneva. 

Left: The "Mellon Blue" could fetch $20 million to $30 million in November. © Christie's

A highlight of the auction year

Christie's auction house presents a very special object in its next "Magnificent Jewels" auction, which will take place on November 11th at the Four Seasons Hotel de Bergues in Geneva.

The Fancy Vivid Blue diamond is a rare natural treasure and highly sought after due to its exceptional color and exceptional clarity. According to Christie's, the 9.51-carat "Mellon Blue" is one of the most valuable diamonds ever to appear on the market. Its value is estimated at between $20,000 and $30,000 million. For decades, the "Mellon Blue" was owned by the American landscape architect, philanthropist, and collector Rachel Lambert Mellon, better known as Bunny Mellon. In her time, Mellon was considered a model of elegance and refinement, with a sense of aesthetics that extended beyond the world of landscape architecture to jewelry. 

A good year for Christie's

The “Mellon Blue” was last shown to the public in 2014, where it was sold at an auction in New York and achieved the highest price for a diamond at auction.

Rajul Kadakia, International Head of Jewellery at Christie's, said in a statement: 

"Christie's auctioned nine of its top 10 jewels in the first half of 2025, resulting in 25 percent growth, with two live auctions in New York and Geneva, where 100 percent of the items went under the hammer. We now look confidently to the second half of 2025 and announce the "Mellon Blue." This stunning Fancy Vivid Blue diamond, once owned by America's Garden Queen, is among the most beautiful colored diamonds ever sold at auction."

The "Mellon Blue" can be admired at Christie's in Hong Kong from October 23 to 28 before its auction and at the Four Seasons de Bergues Hotel in Geneva from November 7 to 11.