The Mellon Blue, a 9.51-carat vivid blue diamond set in a ring, has sold for more than $25 million in Geneva. The price was in line with initial estimates for a stone of exceptional purity, Christie's announced. +Get the most important news from Switzerland in your inbox This vivid blue diamond, which "is among the most beautiful coloured diamonds ever offered at auction", according to Rahul Kadakia, International Director of the Jewellery Department at Christie's, had been estimated by the auction house at between $20 and $30 million. It sold under the hammer for CHF17.4 million, for a final price of $25,592,269 including taxes, according to Christie's. The same stone, then known as the Zoe Diamond, sold for $32.6 million at Sotheby's in New York in 2014, setting world records at the time for a blue diamond and for price per carat. Mounted as a pendant For decades, the stone belonged to Rachel Lambert Mellon, better known as 'Bunny' Lambert Mellon (1910-2014), an American ...