The rectangular-shaped blue stone, mounted on a platinum ring, is the rarest to enter the international market this year.
The anonymous phone bidder, who won after a 15-minute war, has yet to name the gem.
The flawless diamond, which is smaller than a penny, was found in Cullinan mine in South Africa last year, and was the centrepiece of Sotheby’s semi-annual sale in Geneva.
The stone sets a record price per carat for any gemstone sold at auction of $1,349,752, Sotheby’s said.
The previous record price for a fancy vivid blue diamond was $7.9 million, including commission, for a stone weighing 6.04 carats at sale in Hong Kong in October 2007, also by Sotheby’s.
(Source: Reuters / Telegraph)