The centrepiece of Sotheby’s November auction of Magnificent Jewels and Noble Jewels in Geneva - a Fancy Vivid Blue diamond ring by Cartier – has been unveiled in London.
Weighing 8.01 carats, the mesmerising stone has been named ‘The Sky Blue Diamond’, emphasising its highly sought-after hue. It will be offered on 16 November with a pre-sale estimate of $15,000,000–25,000,000.

‘The Sky Blue Diamond’ has been graded Fancy Vivid Blue by the Gemological Institute of America (GIA) – the highest possible colour grading, awarded to no more than 1% of blue diamonds submitted to the GIA. It was also found to have excellent polish and to be of Type IIb, a rare category which represents less than 0.5 % of all diamonds.
Describing the diamond, David Bennett, Worldwide Chairman of Sotheby’s International Jewellery Division, said, "The Sky Blue Diamond is of a wonderfully clear celestial blue, presented in an extremely elegant square emerald cut – in my view, the most flattering of all the cuts for a coloured diamond. This important gem will, I am sure, captivate all collectors of exceptional gemstones."

Within the past two years alone, Sotheby’s has twice set a new world record auction price for a blue diamond, most recently with the only diamond or gemstone in auction history to have exceeded $4 million per carat, the Blue Moon of Josephine (sold for $48.5 million ($4,028,941 per carat) in November 2015).
There will be an opportunity to view the diamond when it is exhibited in London, New York and Geneva ahead of the sale. Full details are listed below.
The Magnificent Jewels and Noble Jewels sale is in Geneva on 16 November.
Exhibition dates
London
13–17 October
New York
4–6 November
Geneva
12–16 November