Legendary 'Mellon Blue' Diamond Heads Back to Auction This November

When it comes to legendary diamonds, few gems carry the mystique, rarity and provenance of "The Mellon Blue." This 9.51-carat Fancy Vivid Blue diamond, once part of the collection of philanthropist and horticultural icon Rachel Lambert “Bunny” Mellon, will once again step into the spotlight at Christie’s Magnificent Jewels sale in Geneva on November 11. The pre-auction estimate is an impressive $20 million to $30 million.

The Mellon Blue is a pear-shaped, Internally Flawless diamond of extraordinary quality. Its deep, mesmerizing blue hue places it among the rarest gems on Earth, with fewer than 0.02% of all diamonds exhibiting natural blue color. These stones owe their vivid shades to trace amounts of boron that enter their crystal lattice during formation — an event that occurs some 400 miles beneath the Earth’s surface, much deeper than most diamonds. This extreme environment, combined with geological happenstance, makes blue diamonds among nature’s rarest miracles.

Blue diamonds have captivated collectors for decades, with record-setting sales across auction houses. The Mellon Blue is no stranger to history-making moments: When it last appeared at auction in 2014, it sold for $32.6 million, setting records for both the highest price paid for a blue diamond and the highest price per carat for any diamond at the time. Now reset as a ring, the stone is poised to enchant the market once again.

Its provenance is as fascinating as its beauty. Bunny Mellon, who died in 2014 at the age of 103, was renowned for her refined taste and elegant lifestyle. She was the wife of financier and philanthropist Paul Mellon and became a cultural tastemaker in her own right. At President John F. Kennedy’s request, she redesigned the White House Rose Garden in 1961, introducing American plant species and creating a graceful outdoor setting, elements of which are still admired today. Mellon also lent her vision to projects in France, including the gardens of her friend Hubert de Givenchy and the restoration of Versailles’ historic Potager du Roi.

Her jewelry reflected the same understated sophistication she brought to her gardens and art collections. The Mellon Blue, with its striking color and flawless clarity, was one of her most prized possessions. Today, it stands as a symbol of her elegance and the enduring allure of blue diamonds.

As Rahul Kadakia, Christie’s International Head of Jewellery, observed, “This stunning Fancy Vivid Blue Diamond, once belonging to America’s Garden Queen, is among the finest colored diamonds to appear for sale at auction.”

That elite club of blue diamonds includes the 15.1-carat “De Beers Cullinan Blue” ($57.5 million, Sotheby’s Hong Kong, 2022), the 14.6-carat “Oppenheimer Blue” ($57.5 million, Christie’s Geneva, 2016) and the 12.03-carat “Blue Moon of Josephine” ($48.5 million, Sotheby’s Geneva, 2015).

With its rare geological origins, storied history and world-class beauty, The Mellon Blue is more than a jewel — it’s a wonderful treasure that continues to capture imaginations and set new standards for what makes a diamond truly extraordinary.

Credit: Image courtesy of Christie's.