The world's largest blue diamond will go under the hammer in Geneva next month, with the rare gem expected to fetch up to $25 million, auctioneers said Friday.
"The Blue", a shimmering pear-shaped rock the colour of cobalt and weighing 13.22 carats was described by Christie's as "the largest fancy vivid blue diamond in the world."
The privately-owned diamond is a "sensational stone," the auction house said, adding that the seller wanted to remain anonymous.
The gem will be the centrepiece of the auction house's "Magnificent Jewels" sale in Geneva on May 14, with an asking price of $21-25 million (15-18 million euros).
If recent auctions in Geneva are any indication though, it could fetch far more.
When the world's largest orange diamond, a 14.82-carat gem called "The Orange", went under the hammer last November at Christie's, it raked in $35.5 million compared to its $17-20 million price tag.
And a Sotheby's auction the next day saw the world's largest pink diamond, known as the Pink Star, fetch $83 million -- $23 million above the asking price.
The auction house was, however, forced last month to take back the Pink Star after the buyer defaulted on the payment.
Christie's said its auction next month would comprise 250 pieces at a joint estimated value of $80 million.
Among other notable gemstones will be a 5.5-carat vivid blue-green diamond named "The Ocean Dream", estimated to be worth up to $9.5 million.
Christie's said the stone was the largest diamond of its kind, stressing that "the combination of its size, natural origin, hue, and saturated colour makes it an extremely unusual occurrence."
A 76.51-carat pink diamond set as a necklace valued at up to $10 million, and a 75.97-carat flawless colourless diamond estimated to be worth up to $15.5 million will also be there to titilate bidders.
Competitor Sotheby's will meanwhile hold its Magnificent Jewels sale next door on May 13, auctioning off one of the world's largest yellow diamonds.
The Graff Vivid Yellow, the colour of a daffodil and weighing 100.09 carats, as been valued at up to $25 million.
A 31.34-carat colourless gemstone called the Victory Diamond will also go under the hammer at the Sotheby's auction.
Named in honour of the Allied victory in World War II and once the property of famous jewellery collector Florence Gould, it is expected to fetch up to $8.0 million.