The mesmerising Mediterranean Blue diamond, the most valuable diamond or jewellery sold so far this year, was purchased by an American private collector for US$21.5 million at Sotheby’s Geneva.

The 10.03-carat fancy vivid blue diamond of VS2 clarity grade is one of the most important blue diamonds to come to market in recent years, according to Sotheby’s. The auction was held on May 13, 2025.

“The diamond attracted enormous interest and was pursued by two determined bidders,” the auction house said. In the end, it sold to a client on the phone represented by Frank Everett, Sotheby’s vice chairman of Jewelry, Americas, on behalf of an American private collector keen to add the blue diamond to her collection.

The blue diamond was mined only last year from the legendary Cullinan mines of South Africa.

Sotheby’s Head of Jewelry, Americas & EMEA, Quig Bruning remarked, “It is undoubtedly the defining stone of the season and ranks among the top blue diamonds we have sold.”

The attention it generated throughout global viewings across the Middle East, Asia and the US, and the auction result itself, reflected the growing appetite for rare and impeccable diamonds, added Bruning.

Sotheby’s High Jewelry auction in Geneva generated CHF42 million (around US$50 million) in total sales, with a 99 per cent sell through by value and 97 per cent by number of lots sold. 

“The auction was marked by extremely strong results for fancy colour diamonds and gemstones and high participation of bidders and buyers from the US who were the majority group in both categories,” revealed Sotheby’s. 

Appetite for blue diamonds was high as two blue diamonds – a 5.83-carat fancy light blue diamond ring and a 4.05-carat fancy blue diamond pendant necklace – also garnered solid buyer interest.

The second most valuable lot was a pair of unmounted cushion-shaped diamonds, weighing 23.88 and 23.76 carats, respectively, and fetching CHF3.2 million (about US$3.8 million). Rounding out the top five lots was a diamond necklace/brooch combination by Van Cleef & Arpels.