Perfection is to be found in this stone: a blue diamond sold at $7.98 million, establishing a new record as the most expensive gemstone per carat bought at auction. The buyer is Moussaieff Jewellers of London, a specialist in rare stones and the stone was sold by a private Asian collector at a Sotheby's auction in Hong Kong.

The 8 minute bidding for the emerald-cut 6.04 carat diamond resulted in its sale for $1.32 million per carat, far higher than the previous record of $926,000 per carat, set by a red emerald-cut diamond, Hancock Red, sold in New York two decades ago.

A carat means 0.2 g. The world's biggest blue diamond is the 45.52-carat Hope Diamond. Still, this is the biggest and rarest vivid blue diamond on offer since Sotheby's Hong Kong auction in 2004, when a similar stone was sold for $ 4.2 million. The rare, vivid blue color of the diamond is said to be induced by the presence of an element called boron in its crystal structure.

"The bidding was fast and furious and you know it's not as if one could go out and buy another one," said Quek Chin Yeow, head of Jewellery Asia at Sotheby's.

"It's as rare as getting a Renoir or a wonderful Rothko. When you look at the stone, it sings. The blue sings. The cutting is wonderful. It has just got such beauty and I mean the fact that it's flawless, it's just an amazing " he said.

The demand for colored diamonds among jewellery collectors is high in Europe, the United States and Asia and blue diamonds come mainly from the Premier Mine in South Africa.

The total sale in Hong Kong's Monday auction was estimated at $ 40.8 million.

An emerald rope-necklace owned by the American songwriter and lyricist Irving Berlin also sold for $2.64 million, including commission, at yesterday's sale.