A stunning blue diamond sold for US$25.6 million while a heritage sapphire brooch fetched US$3.57 million at two separate auctions held in Geneva recently.

Leading Christie’s Magnificent Jewels auction on November 12 was The Mellon Blue, an exceptional fancy vivid IF blue diamond weighing 9.51 carats, which achieved CHF20.52 (around US$25.6 million). 

The blue diamond has become Christie’s highest jewellery lot sold at auction to date in 2025 while the selling price is the third highest for any vivid blue diamond sold at the auction house.

Standing out as one of the finest fancy colour diamonds ever to appear on the market, Mellon Blue was expected to fetch US$20 million to US$30 million. 

The stone belonged to Rachel Lambert Mellon, better known as American horticulturalist, philanthropist and art collector Bunny Mellon (1910-2014). She owned the blue diamond, then set as a pendant, for decades, according to Christie's.

In addition, the sale was framed by three prominent private collections spanning over 150 years of connoisseurship – The Rainbow Collection, a Private JAR Collection, and a Splendid Casket of Ancestral Jewellery, Christie’s said.

Magnificent Jewels realised a total of CHF60.62 million (approximately US$75.6 million), with sell through rates of 95 per cent by value and 94 per cent by lot. 

Max Fawcett, global head of Jewellery from January 2026, said the results reflect a market defined by confidence and discernment, adding that attractive estimates and a curated collection drove competitive bidding across platforms.

Meanwhile, Phillips’ Geneva Jewels Auction: V generated CHF13.7 million (about US$17 million) on November 10, with the Vanderbilt Family Jewels leading the sale. A total of 96 lots were sold out of 114 that were offered.

The star lot was “The Vanderbilt Sapphire” brooch by Tiffany & Co featuring a 42.68-carat sugarloaf Kashmir sapphire and diamonds. Dating back to the early 20th century, the brooch is a Belle Epoque masterpiece from the Gilded Age. It fetched CHF2.87 million (about US$3.57 million).

The Vanderbilt Family Jewels collection was 100 per cent sold, soaring to CHF3.42 million (around US$4.25 million). Signed jewels achieved standout results, with 90 per cent of lots sold and the majority far exceeding their pre-sale high estimates. 

Phillips’ Worldwide Head of Jewellery Benoît Repellin said auction results attest to the enduring appeal of period jewels and the discerning eye of international clients. 

The event drew over 1,600 visitors during the preview and sale, reflecting significant interest from collectors and enthusiasts. Bidders from 44 countries participated in person, over the phone and online.