London luxury jeweller Laurence Graff has paid a record 8.2 million Swiss francs (NZ$10.8 million) for a Burmese ruby, the top lot at a Geneva auction marked by strong prices for fine diamonds and rare coloured stones.

Graff, known as the “King of Diamonds”, was buying the ruby of 8.62 carats for the second time, having acquired it first at an auction eight years ago. He had named the ‘pigeonblood’, or pure red with a hint of blue, gemstone the “Graff Ruby” at the time.

In between he sold it to Greek financier Dimitri Mavromattis, whose collection of 16 jewels was part of Sotheby’s semi-annual sale in Geneva. In all, 403 gems netted a total of 91.8 million francs.

“This is the finest ruby in the world. We are very proud to have it in our possession for the second time,” Graff said in a Sotheby’s statement. The cushion-shaped ruby, set in a diamond ring, is from the Mogok Valley of Myanmar which produces “arguably the rarest of all gemstones”, Sotheby’s said.

“It’s not a surprise, the ruby is a unique stone that bears his name. He likes unique stones,” Eric Valdieu, a Geneva-based jeweller formerly of Christie’s who attended the sale. “Its price more than doubled in just over eight years.” “Coloured stones brought strong prices,” Valdieu said, noting that a 27.54 carat Kashmir sapphire sold for a record 5.7 million francs. Sotheby’s said an Asian collector bought it.