The sale included a fancy greyish-blue, 2.97-carats step-cut diamond, set in a ring designed by the society jeweller Andrew Grima. The piece achieved £1.5m against its pre-sale estimate of £500,000 to £700,000 – setting a new world record price per carat for a fancy greyish-blue diamond and a new world record for a Grima creation.
The other top lot – a pair of late 19th Century earrings set with two cushion-cut 7.92-carats and 7.96-carats Kashmir sapphires which were the property of an unnamed European princess – achieved £1.5m against its pre-sale estimate of £500,000 to £800,000.
Jean Ghika, director of jewellery for UK and Europe at Bonhams, said: “These lots attracted interest from around the globe because of their exceptional quality and rarity. The prices achieved reflect the buoyancy of the market for coloured gemstones of the highest quality.”
Rubies from Burma and Madagascar also sold well with a Belle Époque ruby and diamond pendant circa 1915, set with al 3.83-carats Burmese ruby, sold for £128,500 to a telephone bidder – triple its high estimate of £40,000.
In addition, a 10.28-carats Madagascan ruby single-stone ring sold for £236,500, setting a new world record price per carat.
In total, the sale achieved £6.79m, with 88% of lots sold by value.