The Famous 'Mellon Blue' Diamond Sells for $25.6 Million in Geneva

The celebrated 9.51-carat, pear-shaped “Mellon Blue” diamond was the centerpiece of the “Magnificent Jewels” auction recently hosted by Christie's in Geneva. The highly anticipated sale concluded on November 11, 2025. The final price realized, inclusive of all buyer's premiums and fees, amounted to 20.5 million Swiss francs, which translates to the equivalent of 25.6 million US dollars. This outcome was particularly notable because the sum achieved was lower than the impressive price the stone had commanded during its previous appearance on the market in 2014, a fact that observers suggest reflects the current, fluctuating nature of the market for truly exceptional colored gemstones.

The diamond boasts impeccable provenance, having once belonged to Rachel Lambert Mellon, who was universally known as Bunny Mellon. She was a renowned philanthropist, collector, and gardening expert, earning the affectionate title, the “Queen of American Gardens,” for her significant contributions to landscape architecture, including her famous redesign work at the White House. Christie's had set a pre-sale estimation for the stone in the broad range of $20 million to $30 million. The final price confirmed that while demand for these rare blue diamonds remains robust, buyers are exercising a degree of caution. Furthermore, the diamond is technically classified as an elite Type IIb, a category reserved for less than 0.1% of all diamonds, underscoring its extraordinary rarity and chemical purity.

The gem has a storied past, having previously set a world record. Following Bunny Mellon's passing at the age of 103, the very same stone—then known as the “Zoe Diamond”—was sold in 2014. That sale achieved a staggering $32.6 million when it was acquired by billionaire Joseph Lau. It is noteworthy that prior to the 2014 auction, the stone underwent a precise re-cutting process, which reduced its weight slightly from 9.75 carats to its present 9.51 carats. This meticulous modification was undertaken specifically to enhance its clarity, successfully upgrading its rating from VVS1 to the highest possible grade, IF (Internally Flawless).

Although the recent sale yielded a more modest financial result compared to the record set a decade earlier, it still affirms that the intrinsic value of such artifacts is ultimately dictated by their unique historical provenance and impeccable physical characteristics. Rahul Kadakia, Christie's International Head of Jewelry, remarked that the price achieved demonstrates an “elite appetite among collectors for extraordinary and legendary jewels.” Adding historical perspective, Max Fawcett, Christie's Head of Jewelry in Geneva, suggested the stone symbolizes “the lifestyle of a bygone era—one only possible with Gilded Age wealth.”

Market analysts also pointed to external macroeconomic factors, such as geopolitical tensions and the economic slowdown observed in China, which may have contributed to buyer caution during the recent bidding. Nevertheless, the successful transaction reinforces the enduring appeal of historically significant gems. It is important to note, however, that the overall record for blue diamonds remains held by larger specimens, such as the “Oppenheimer Blue” and the “Cullinan Blue,” which commanded higher prices in previous high-profile auctions.