A Fancy Intense Blue diamond went under the hammer at Bonhams Fine Jewellery sale in London this week.
The pear-shaped 4.03 carat precious stone, which has been held in a private collection for nearly 30 years, was snapped up for £2,68m.
Graff Diamonds, who bought the gem, paid £638,464 per carat.
Jean Ghika, Head of Jewellery, Bonhams UK & Europe, said: “Our top lots performed extremely well with global buyers vying for the prize lots.
“The blue diamond and Kashmir sapphire both achieved strong hammer prices, demonstrating discerning collectors will always seek out the best examples when it comes to fine gemstones.”
Staying with coloured diamonds, the second headline lot also attracted interest from Bonhams’ clients during its preview in London, Geneva, New York and Hong Kong. The Fancy Coloured Diamond brooch dates from the mid-20th century and sold for £725,000.
The second highest value lot sold during the sale was A Kashmir sapphire single-stone ring, weighing 9.61 carats. The octagonal step-cut sapphire has no indications of heating and went under the hammer for £845,000.
Earlier this year Magnificent Jewels and Jadeite Sale in Hong Kong Sotheby’s set a new world auction record for any gemstone at auction as the Pink Star sold for more than $71m (£57m).