November 4, 2015 / 9:25 PM / 3 years ago

"Once in a blue moon diamond" could fetch up to $55 million: Sotheby's

GENEVA (Reuters) - A large blue diamond, one of the world’s rarest, could fetch $35-55 million at auction next week, Sotheby’s said on Wednesday, as an industry group reported strong prices for color diamonds ahead of the holiday season.

A model poses with a 12.03 carats cushion-shaped fancy vivid blue diamond mounted on a ring at Sotheby's auction house in Geneva, Switzerland November 4, 2015. REUTERS/Denis Balibouse

The Nov. 11 sale also features a Cartier pearl and diamond tiara - estimated at up to $450,000 - that survived the sinking of the Lusitania cruise liner 100 years ago, and a 15.20 carat fancy orange-pink diamond pendant owned by former James Bond actor Sir Sean Connery, estimated at $1.2-$2.4 million.

The flawless “Blue Moon Diamond”, which weighs 12.03 carats and is mounted on a ring, is the star lot of more than 500 on offer at Sotheby’s semi-annual jewelry sale in Geneva.

“The market for vivid blue diamonds of this level, it’s so rare. Each stone is individual, in a sense,” David Bennett, worldwide chairman of Sotheby’s international jewelry division, told Reuters.

“The GIA (Gemological Institute of America) graded 400 blue diamonds and only four of the 400 were graded (fancy) vivid blue. So even amongst this extremely rare class of blue diamonds, to get one vivid blue, 12 carats, internally flawless, is once in a blue moon,” he said.

The stone was discovered in South Africa’s famed Cullinan mine in January 2014 and cut into a cushion shape from a 29.62 carat rough crystal. Its current owner, New York-based jeweler Cora International, bought it from Petra Diamonds, the mine’s owner, according to Sotheby’s.

“You’re looking at something that, by a freak of n