Christies's auction house shows the 'Oppenheimer Blue,' a rare fancy vivid blue diamond weighing 14.62 carat. (AFP Photo)
A dazzling blue diamond once owned by mining magnate Philip Oppenheimer could fetch a record sale price Wednesday, with auction house Christie's hoping it tops the staggering $48.4 million mark set last year.
The 14.62-carat "Oppenheimer Blue" is the largest stone in the exceptionally-rare Fancy Vivid Blue category ever to go under the hammer, according to Christie's, which has valued the gem between $38 million (34 million euros) and $45 million.
But experts said it has a chance to beat the record set by Sotheby's in November with Hong Kong billionaire Joseph Lau's purchase of the 12.03-carat "Blue Moon of Josephine".
The Oppenheimer Blue "is highly likely to break the $50 million mark to become the most expensive polished diamond ever sold at auction," said Tobias Kormind, managing director at 77diamonds.com
Sotheby's fetched a record price in the Fancy Vivid Pink Category on Tuesday, when a private buyer in Asia scooped up a 15.38-carat stone for $31.6 million.
Ehud Laniado, president of Cora International which sold the stone dubbed "Unique Pink", said he was "very happy with the sale price", and voiced confidence that the gem's value would rise over time.
"When you buy a Picasso, you pay a lot, but you know you are going to sell it for even more," Laniado told news agency AFP.
Sotheby's also sold a blue diamond, weighing 7.32 carats, for $17.1 million.
A recent spate of eye-popping bids at Geneva's semi-annual magnificent jewel auctions has highlighted the surging value of precious stones, with some of the world's ultra-rich increasingly investing in hard assets as a safeguard against stock market volatility.
A woman holds up the 'Oppenheimer Blue,' a rare fancy vivid blue diamond weighing 14.62 carat. (AFP Photo)
Britain's Sir Philip Oppenheimer (1911-1995) led a powerful cartel called the Central Selling Organization for 45 years, tightly controlling roughly 80 percent of the international diamond trade in a bid to prevent wild price swings.
De Beers, the giant mining company built by the Oppenheimer family, also flourished in the latter half of the 20th Century, thanks in part to Sir Philip's outsized influence in the sector.
The blue stone has passed through several hands since Oppenheimer's death and Wednesday will mark its first appearance at public auction.
But, there is always a chance that the jewel will not even meet its estimated floor price.
That happened last month when a 9.54-carat blue diamond ring once owned by American child star Shirley Temple failed to sell at auction in New York after bidding closed at $22 million, below the reserve price.
Christie's has valued its total of 280 lots up for auction on Wednesday at $113 million. The collection includes 46 pieces from German-born princess Gabriela zu Leiningen, who was married to the Aga Khan.
Sotheby's 495-lot auction brought in $171.1 million, with 70 percent of the items selling above their estimated price, the company said in a statement.
A quarter of auction participants were from Asia, Sotheby's said, underscoring the region's growing buying power, especially among tycoons based in Hong Kong.