Iconic 'Mellon Blue' diamond sells for $25.6 million at Geneva auction

A vivid 9.51-carat Mellon Blue diamond, embedded in a serpentine ring, was sold for $25.6 million at an auction in Geneva on Tuesday. The eccentric diamond was owned by US art collector Bunny Mellon.

The auction was conducted by Christie’s during its Magnificent Jewels sale at the Hotel des Bergues. The Mellon Blue was sold for 20,525,000 Swiss francs, though it had been estimated to fetch 16 to 24 million francs.

The diamond actually belonged to Rachel Lambert Mellon, better known as Bunny Mellon, who was an art collector and a US horticulturist. After her death at the age of 103, the diamond was last sold at a New York auction in 2014.

It is now, in 2025, that the Mellon Blue has caught the eye of another avid collector of precious jewels and gems. Max Fawcett, head of jewellery at Christie’s in Geneva, said, “It has also become symbolic of a lifestyle of a bygone era, the type only possible with a Gilded Age fortune.”

The stone, so beautifully embedded in the ring, was graded internally flawless.

Another jewellery sale is set to take place on Wednesday in Geneva by Sotheby’s, which will present a brooch embellished with old mine-cut diamonds.

This brooch was once owned by French emperor Napoleon Bonaparte and was seized from him after he fled following the Battle of Waterloo in 1815. It is expected to sell for $150,000 to $250,000.

A rare 10.08-carat naturally pink diamond will also be available at the auction, and this sparkling piece is expected to fetch around $20 million.