A rare "fancy vivid blue" diamond ring was on display in Geneva on Wednesday (November 8), ahead of next week's auction where it is expected to fetch up to $25 million (£20,142,609).
The gem, named "The Sky Blue Diamond", weighs 8.01 carats and was mounted on a ring by jeweller Cartier.
It will be sold on November 16 at Sotheby's "Magnificent Jewels and Noble Jewels" auction in Geneva, with a pre-sale estimate of $15 million-$25 million.
In the past two years, Sotheby's has twice set a new world record auction price for a blue diamond, most recently with the Blue Moon of Josephine, sold for $48.5 million (more than $4 million per carat) in November 2015.
Among other items to be auctioned by Sotheby's is a diamond necklace of Russian royal provenance. Catherine the Great, who ascended to the Russian throne in 1762, is said to have commissioned this necklace.