A scintillating 6.03-carat cushion-shaped Fancy Vivid Blue diamond is set to take center stage at Sotheby's Geneva High Jewelry sale on May 12. Described as “exceptional and rare,” this remarkable gemstone carries a pre-sale estimate of CHF 7.2 million to 9.6 million (approximately $8 million to $10.7 million).
Graded Fancy Vivid Blue — the highest possible color designation for a blue diamond — the gem displays a rich, saturated hue that is both intensely vibrant and mesmerizingly pure. Adding to its allure is its internally flawless clarity and a size that is exceedingly scarce for diamonds of this caliber.
Blue diamonds owe their captivating color to trace amounts of boron within their crystal structure. This element absorbs yellow light, allowing the blue wavelengths to shine through. But their uniqueness doesn’t end there.
Unlike traditional colorless diamonds, which form about 90 to 140 miles beneath the Earth’s surface, blue diamonds originate far deeper — sometimes up to four times deeper — within the planet’s mantle. A blue diamond's extraordinary journey to the surface, often involving ancient tectonic activity and subduction zones, adds another layer of intrigue to these already extraordinary gems.
The featured diamond’s provenance further elevates its status. The gem was unearthed at the legendary Cullinan Mine in South Africa, a source synonymous with some of the world’s most important diamonds. This historic mine produced the 3,106-carat Cullinan Diamond — the largest gem-quality diamond ever discovered — as well as a lineage of famous blue diamonds that have shattered auction records.
Among them are the 15.10-carat De Beers Cullinan Blue, which sold for $57.5 million in 2022, the 12.03-carat Blue Moon of Josephine, which achieved $48.4 million in 2015 and the 14.62-carat Oppenheimer Blue, which fetched $57.5 million in 2016. These headline-grabbing sales highlight a clear trend: blue diamonds consistently rank among the most valuable gemstones ever sold at auction, often commanding the highest prices per carat.
Earlier in 2026, the Cullinan Mine produced a 41.82-carat rough blue diamond that is expected to become one of the most important blue diamonds ever found.
Fewer than 0.3% of all diamonds exhibit a predominantly blue color, and only a tiny fraction of those earns the coveted Fancy Vivid grade. When combined with exceptional clarity and a desirable size, Sotheby's headliner is a gem in rarefied company.
Credits: Images courtesy of Sotheby's.