£6.2 million world record for Bonhams blue diamond

The rare gem was bought by Graff Diamonds, the international diamond house headquartered in New Bond Street, London. Bidding came from around the world via 25 telephone lines, as well as from bidders in the packed saleroom.

The fancy deep-blue diamond is set horizontally within a mount pavé-set with brilliant-cut diamonds and courses of baguette-cut diamonds in a ‘Trombino’ ring made by Bulgari, the renowned Italian jeweller favoured by Hollywood film stars, and the epitome of fashion and innovation during the 1960s. The ring was made circa 1965 and had been estimated to fetch £1 million to £1.5 million at the Bonhams auction.

The extraordinary colour blue is derived from small atoms of boron mixing with the carbon atoms in a diamond, affecting the absorption of light passing through the stone and lending it a blue appearance. Blue diamonds are structurally very pure and account for less than one per cent of all diamonds mined.

Jean Ghika, director of Bonhams Jewellery Department for Europe, commented after the sale: “We are delighted with the price it has made. It was a sensational stone which charmed everyone who viewed it prior to the sale. Blue diamonds, especially those over five carats, are extremely rare to see on the market and continue to be highly sought after. We are honoured to have handled the sale of such a unique gem.”