A rare blue diamond pendant known as the Mellon Blue, owned by art collector Rachel Lambert “Bunny” Mellon, sold for $25.5 million at Christie’s Magnificent Jewels auction in Geneva on Tuesday. The 9.51-carat fancy vivid blue, internally flawless pear-shaped diamond had a pre-sale estimate of $20–30 million. This price is 22 percent less than the $32.6 million it achieved at Sotheby’s in 2014 as part of Mellon’s collection sale, and nearly 60 percent less when adjusted for inflation. The buyer was not disclosed.
The sale matters because it highlights shifting dynamics in the high-end jewelry market, where even the rarest gems are not immune to value depreciation over time. The Mellon Blue’s decline in price contrasts with record-breaking blue diamond sales in previous years, such as the Oppenheimer Blue and De Beers Cullinan Blue, each fetching $57.5 million. The result also underscores the enduring but fluctuating appeal of storied gems tied to prominent collectors like Bunny Mellon, whose legacy as a tastemaker and art patron continues to influence market interest.