A huge, flawless blue diamond sold for a record $9.5 million on Tuesday (May 12), making it the highest price paid per carat for any gemstone at auction, according to Reuters.

The stone was a rectangular-shaped blue stone, weighing in at 7.03 carats. It was said to be the rarest to enter the international market this year.

It sold to an anonymous buyer bidding by telephone after battling it out with another caller for nearly 15 minutes.

The blue diamond was the centerpiece of Sotheby's semi-annual sale in Geneva. Chairman David Bennett said the results showed the rare jewelry market's resilience despite the economic downturn.

"This is already a new world record price...," Bennett told reporters. "It is fantastic in this market and shows that these rare things are very much in demand."

At over $1.3 per carat, the stone sets a record price per carat for any gemstone sold at auction, Sotheby's said.

The previous record price for a fancy vivid blue diamond was $7.9 million, including commission, for a stone weighing 6.04 carats at sale in Hong Kong in October 2007.

It was extracted in 2007 from the historic Cullinan mine in South Africa, the world's most regular supplier of blue diamonds of size and quality. According to the report, blue are the rarest of the diamond family after reds.

"To have a stone mined last year and cut the early part of this year so it is absolutely virgin coming straight from the mine has never happened before," Bennett said. "This is one of the extremely rare substances in our universe."

Reuters reports that the auction took $35.7 million in sales for 266 lots which found new owners, while another 80 pieces were not sold. The report said that blue are the rarest of the diamond family after reds.