A 10-carat fancy vivid blue diamond, named “The Mediterranean Blue,” stunned collectors and enthusiasts alike when it sold for $21.5 million at Sotheby’s, becoming the most valuable jewel sold in 2025. The diamond’s rarity, beauty, and origin combined to tell a story of geological wonder and meticulous craftsmanship.
A bidding war for a rare gem
At Sotheby’s High Jewelry auction in Geneva this week, a dazzling spectacle unfolded as one of the world’s rarest blue diamonds took center stage. “The Mediterranean Blue,” a 10.05-carat fancy vivid blue diamond, captured the attention of global collectors and ultimately sold for $21.5 million after a competitive bidding session lasting nearly three minutes.
Opening at CHF 9 million (approximately $10.7 million), the bidding escalated quickly before the diamond was secured by an American private collector. Represented by Sotheby’s vice chairman of jewelry for the Americas, Frank Everett, the collector won the lot with a final bid slightly above its pre-sale estimate of CHF 18 million ($20 million).
Auctioneer Quig Bruning, Sotheby’s head of jewelry for the Americas and EMEA, described the moment as “an extraordinary honor” and hailed the stone as “the defining jewel of the season.” According to Sotheby’s, it is the most valuable diamond or jewel sold at auction this year.
What makes the mediterranean blue exceptional
The allure of “The Mediterranean Blue” goes far beyond its carat weight or price tag. Classified as a Type IIb diamond—an incredibly rare category comprising less than 0.5 percent of all diamonds—it boasts not only rarity but also superior quality. Its color, graded “fancy vivid blue” by the Gemological Institute of America (GIA), is the highest grade possible for a blue diamond, indicating both depth and brightness of hue.
Fancy vivid blue diamonds are extremely rare; fewer than 0.1 percent of diamonds exhibit any trace of blue coloration, and only a fraction of those qualify for the vivid grading. This places “The Mediterranean Blue” among an elite class of gems, revered not only by gemologists but also by elite collectors and investors worldwide.
What also sets the diamond apart is its origin. The stone was cut from a 31.94-carat rough diamond discovered in 2023 at the historic Cullinan mine in South Africa—a source known for yielding some of the world’s most famous diamonds. These include the 530-carat “Great Star of Africa,” as well as other legendary blue stones such as the 12.03-carat “Blue Moon of Josephine,” which sold for $48.5 million in 2015, and the 15.10-carat “De Beers Blue,” which fetched $57.5 million in 2022.
From rough to radiant: A process of precision
Transforming a colored rough diamond into a finished gem is one of the most challenging tasks in the industry. For “The Mediterranean Blue,” the process took more than a year of analysis and planning. Achieving the ideal balance between carat weight, clarity, and color saturation requires both scientific precision and artistic vision.
After extensive modeling and simulation, the team opted for a cushion modified brilliant cut—a classic choice known to enhance both color and light performance. The final six-month cutting process yielded a gem that Sotheby’s called “a timeless relic and a contemporary masterpiece.”
The diamond was ultimately set in a ring for the auction. However, during its promotional tour across the Middle East, Asia, and the United States, it was also featured in a custom-designed brooch by American jewelry designer Lauren Harwell Godfrey. Commissioned by Everett, the piece was inspired by the 2024 Met Gala theme “Superfine: Tailoring Black Style” and offered a fresh creative perspective on how the stone could be worn.
From Abu Dhabi to Geneva: A global exhibition
Before arriving at the auction block in Geneva, “The Mediterranean Blue” embarked on a global tour. Its first public appearance was during Sotheby’s debut high jewelry exhibition in Abu Dhabi, where it headlined a showcase of eight exceptional diamonds and gemstones valued at over $100 million.
The tour reflected a growing trend in the auction world—creating immersive experiences for elite collectors who now span regions like the Middle East and Asia, not just traditional European or American markets. Sotheby’s global strategy paid off, as the diamond generated buzz and captivated audiences across continents before making its way back to Europe for the final sale.
Its journey mirrors a shift in the global jewelry landscape, where rare colored diamonds are increasingly seen as both symbols of luxury and resilient investment assets. As Bruning observed, “the excitement it has generated throughout its global exhibition tour… reflects the growing global appetite for rare and impeccable diamonds, and a marked flight to quality among collectors.”
A record, and a reflection of a larger trend
While $21.5 million may not surpass some of the stratospheric prices paid for colored diamonds in the last decade, the sale of “The Mediterranean Blue” underscores a consistent truth in the world of fine jewelry: rarity and beauty will always command attention and value.
With fluctuating markets and increased interest in tangible assets, top-tier colored diamonds are attracting not only collectors but also investors seeking stable long-term value. Their finite supply and the meticulous skill required for their creation make each stone a singular achievement—one that bridges nature, science, and design.
In the case of “The Mediterranean Blue,” the diamond’s journey from the mines of South Africa to the hands of a discerning American collector tells a story that spans continents, cultures, and centuries of craftsmanship.
