Rare 'blue moon' diamond could fetch up to $55m

The flawless stone which weighs 12.03 carats is available at Sothebys jewellery sale in Geneva.

FILE: A 29.6 carat blue diamond has been discovered at a South African mine by Petra Diamonds. Picture: www.petradiamonds.com.

GENEVA A large blue diamond, one of the worlds rarest, could fetch between $35-55 million at an auction next week, Sothebys said on Wednesday, as an industry group reported strong prices for colour diamonds ahead of the holiday season.

The 11 November 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 Sothebys semi-annual jewellery sale in Geneva.

The market for vivid blue diamonds of this level, its so rare. Each stone is individual, in a sense, David Bennett, worldwide chairman of Sotheby's international jewellery 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 Africas 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 jeweller Cora International, bought it from Petra Diamonds, the mines owner, according to Sotheby's.

Youre looking at something that, by a freak of nature, has been brought up by a volcano. Its just so extraordinary that this diamond would have stayed forever, miles under the earths surface...Its like the most secret part of the earth has just been shown to us, Bennett said.

In the third quarter of 2015, the best performing fancy colour diamonds were vivid blues, whose price rose up to 6 percent over the previous quarter, while prices for white diamonds showed declines of 6 to 10 percent, the Fancy Color Diamond Index said in an overnight statement.

The index is published by the Fancy Color Research Foundation, a non-profit industry-backed group based in Israel that tracks wholesale pricing data for yellow, pink and blue fancy colour diamonds in Hong Kong, New York and Tel Aviv.

A 8.48-carat pigeons blood ruby ring that was given to the last Queen of Italy, Maria-Jose, for her wedding to Crown Prince Umberto in 1930 is estimated at $6 million-$9 million, Sothebys said.

At rival Christies sale on Nov. 10, the largest cushion-shaped fancy vivid pink diamond ever to come to auction is estimated at $22.12-$27.15 million.