Sotheby’s has announced it will auction an “extremely rare” fancy-vivid blue diamond ring by Cartier, which could fetch up to $25m (£20.3m).
‘The Sky Blue Diamond’ will be one of the star lots at Sotheby’s Geneva Jewellery sale on 16 November and will be exhibited in the auction house’ New Bond Street galleries from 13 to 17 October.
It has been graded fancy-vivid blue by the Gemological Institute of America (GIA) – the highest possible colour grading, awarded to only around 1% of blue diamonds submitted to the GIA.
The diamond, weighing 8.01 carats, was also found to have “excellent polish” and to be of Type IIb, a rare category applicable to less than 0.5 % of all diamonds.
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 Sotheby’s has twice set a new world-record auction price for a blue diamond, including the 12-carat Blue Moon of Josephine which sold for £31.8m.