Geneva – A rare blue diamond known as the “Mediterranean Blue” sold for just over $20 million at Sotheby’s in Geneva this week, after a tense three-minute bidding battle between two prospective buyers.
Despite the impressive price tag, experts say the result fell slightly short of industry expectations amid wider global economic uncertainty. The 17.61-carat cushion-cut gem, which was discovered in South Africa’s famed Cullinan mine, was the centrepiece of Sotheby’s latest Magnificent Jewels sale.
Marketed as the “flagship stone of the season,” the diamond had been unveiled to collectors and enthusiasts in Abu Dhabi earlier this year, drawing attention for its intense hue and remarkable clarity.
“Blue diamonds are at the top of the pyramid of rarity,” said Quig Bruning, head of Sotheby’s Jewellery for North America, Europe, and the Middle East. “This is undoubtedly the flagship stone of the season and ranks among the best blue diamonds we have sold.”
The auction opened with a CHF9 million ($10.1 million) bid and quickly escalated in a spirited exchange that lasted nearly three minutes. In the end, the winning bid came from a private American collector, whose identity was not disclosed.
Sotheby’s reported “enormous interest” in the Mediterranean Blue ahead of the sale, which contributed to the final hammer price surpassing the diamond’s pre-sale estimate of $20 million. Still, reactions from industry insiders were mixed.
Tobias Kormind, director of 77 Diamonds, Europe’s largest online jewellery retailer, described the outcome as “less impressive” than initially anticipated.
“The diamond exceeded its $20 million estimate, which suggests significant interest,” he said. “But general uncertainty, including trade tensions between the US and China, may have dampened bidder confidence.”
Sotheby’s has long regarded blue diamonds as highly desirable collector’s items. Their scarcity — especially when paired with significant size and quality — ensures high demand among elite buyers.
According to the auction house, discovering a blue diamond remains an “incredibly rare event,” and those found in the Cullinan mine are among the most sought after globally.
The sale of the Mediterranean Blue adds to a growing list of record-setting coloured diamonds that have passed through Sotheby’s hands in recent years.
However, analysts suggest that the current global economic climate is encouraging even high-net-worth buyers to exercise caution.
Despite some industry hesitation, the diamond’s successful sale reinforces the resilience of the ultra-high-end jewellery market, particularly for rare and coloured gems.
The Mediterranean Blue now joins the exclusive ranks of famous diamonds auctioned in Geneva, which remains one of the world’s premier centres for high-value jewellery sales.
As the spring auction season continues, all eyes will be on whether other notable lots can meet or exceed expectations in a market increasingly shaped by geopolitical developments and economic volatility.