The Mellon Blue Diamond
The Mellon Blue Diamond is a 9.51-carat Fancy Vivid Blue diamond celebrated for its exceptional color, purity, and provenance. Pear-shaped and graded by the Gemological Institute of America (GIA) as Fancy Vivid Blue, Internally Flawless, it stands among the finest natural blue diamonds known to date.
© Christie’s Auction House
Origin and Provenance
The diamond takes its name from Rachel Lambert “Bunny” Mellon (1910–2014), an American philanthropist, art collector, and horticulturalist renowned for her refined taste. Her personal collection included rare artworks, jewels, and historical pieces of great significance. The Mellon Blue was part of her private jewelry collection and remained unseen by the public for many years.
Following Mrs. Mellon’s passing, the diamond resurfaced as a privately held treasure, admired for its extraordinary hue and condition. In 2025, Christie’s announced its inclusion in the Magnificent Jewels sale in Geneva, highlighting its rarity and provenance.
Characteristics
The Mellon Blue Diamond weighs 9.51 carats and exhibits the purest shade of Fancy Vivid Blue — the highest color grading for blue diamonds, signifying both intensity and saturation. Its Internally Flawless clarity means the stone is free from internal inclusions visible under 10× magnification, a trait that dramatically enhances both brilliance and value.
Blue diamonds owe their color to trace amounts of boron within the carbon lattice structure, a geological phenomenon that occurs under immense heat and pressure deep within the Earth. This boron presence bends light in unique ways, producing the cool, vivid blue tone that defines this rare category of diamonds.
Comparisons and Significance
Within the world of colored diamonds, stones like the Mellon Blue occupy an elite position. Its attributes invite comparison to some of the most renowned blue diamonds ever sold at auction, including the Oppenheimer Blue (14.62 carats, sold for $57.5 million in 2016) and the Blue Moon of Josephine (12.03 carats, sold for $48.5 million in 2015).
While its auction journey continues to shape its modern story, the Mellon Blue’s greater significance lies in what it represents: the merging of natural wonder, human craftsmanship, and personal heritage. Its perfect balance of size, color, and provenance positions it among the world’s most distinguished blue diamonds — a modern classic destined for historical recognition.
Legacy
As part of the broader narrative of rare blue diamonds, the Mellon Blue contributes to our understanding of how geology, artistry, and history converge in the formation and appreciation of extraordinary gems. Whether in private ownership or public view, it stands as a symbol of refinement and permanence — a diamond whose story reflects the enduring fascination with nature’s rarest creations.
