Sotheby's To Auction 12-Carat Blue Moon Diamond

An extremely rare and large blue diamond will be the centerpiece of Sotheby's Magnificent Jewels and Noble Jewels sale in Geneva on 11 November 2015.

"The Blue Moon", among the largest known cushion-shaped vivid blue diamonds, weighs 12.03 carats and has been graded Fancy Vivid Blue by the Gemological Istitute of America. This is the GIA's highest possible colour grading for blue diamonds.

David Bennett, Chairman of Sotheby's International Jewellery Division, commented: "Blue, for me, is the most mysterious and magical of all the colours of diamond, and the Blue Moon will now take its place among the most famous gems in the world."

The spectacular stone was discovered last year at the famous Cullinan mine in South Africa by Petra Diamonds and originally weighed in at 29.93 carats before its transformation.

The Blue Moon is expected to fetch between $35 million and $55 million.