A rare blue diamond unearthed from South Africa’s renowned Cullinan mine has sold for $21.5 million at a Sotheby’s auction in Geneva. Known as “The Mediterranean Blue,” the 10.3-carat gem, graded as fancy vivid blue, exceeded its $20 million estimate following an intense bidding war.
The auction began at 9 million Swiss francs ($10.8 million) and concluded with a final sale to an anonymous U.S. collector for 17.9 million Swiss francs ($21.5 million), Sotheby’s confirmed.
Unveiled earlier this year, the Mediterranean Blue quickly drew industry attention and was showcased last month in Abu Dhabi alongside a curated collection of high-value gems worth over $100 million.
Sotheby’s head of jewels for North America, Europe, and the Middle East, Quig Bruning, described the diamond as “undoubtedly the defining stone of the season,” highlighting its exceptional rarity and appeal.
Tobias Kormind, director of Europe’s largest online diamond retailer 77 Diamonds, noted that while the sale exceeded expectations, market uncertainty—particularly ongoing US-China trade tensions—may have tempered bidding enthusiasm.
Despite the subdued atmosphere, the sale reinforces the global appetite for extraordinary gemstones and underscores South Africa’s enduring legacy in the world of precious diamonds.