On Nov. 11, Christie’s is sending The Mellon Blue, a 9.51 ct. Fancy Vivid Blue pear-shape diamond once belonging to philanthropist and style icon Rachel Lambert “Bunny” Mellon, to the auction block during its Magnificent Jewels auction in Geneva. Estimated to achieve between $20 million and $30 million, the stone is already being considered one of the most important diamonds to appear on the market in recent years.
Fancy Vivid Blue diamonds are the rarest category of blue stones, representing a fraction of 1 percent of global diamond discoveries. At 9.51 carats, the Mellon Blue sits firmly in the top tier of the category, its pear-shape cut intensifying both its saturation and brilliance. In recent years, Fancy Vivid Blue diamonds have dominated auction headlines, with prices routinely climbing above $2 million per carat.
Named after the Mellon family and most recently owned by Bunny Mellon, the diamond has a provenance that enhances its allure. Famed for her refined taste and influence in art, design, and horticulture, Bunny was a prominent American philanthropist and a major patron of the arts. Notably, in 1961, President John F. Kennedy invited her to redesign the Rose Garden, where she introduced American plant species and created an open, elegant space suited for public ceremonies, work that is still visible today. Her efforts extended beyond Washington: In France, she designed the gardens of her close friend Hubert de Givenchy’s estate and contributed to the restoration of the historic Potager du Roi at the Château de Versailles.
“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,” said Rahul Kadakia, international head of jewelry at Christie’s, in a statement.
At top: The Mellon Blue 9.51 ct. Fancy Vivid Blue pear-shape cut diamond, estimate $20 million–$30 million
(Photos courtesy Christie’s Images Ltd. 2025)