The Beau Sancy diamond, which has been owned by some of Europe's most famous royal figures, sold last night (May 15) for $9.7m at Sotheby's in Geneva.
In doing so, the 34.98 carat rose-cut jewel, which has never been owned by a non-royal, doubled its pre-sale estimate.
The Beau Sancy is the smaller version of the Grand Sancy, which can be seen at the Louvre in Paris.
The oldest diamond ever to arrive at auction, the Beau Sancy is thought to have begun life in Golconda, India, and was first acquired by the Lord of Sancy in Constantinople.
In 1604, Sancy sold the gem to French king Henri IV, whose wife Marie de Medici had expressed a strong desire to own it.
"She wanted that stone as soon as she knew that Nicolas de Harlay had sold le Grand Sancy to the king of England, James I, for his wife," a spokesperson for Sotheby's told France's Parisien newspaper.
Marie wore it on top of the crown for her 1610 coronation, the day before Henri was assassinated.
In 1631 the Queen fled into exile and the diamond was sold to the Dutch royal family; it was used to seal the wedding of Willem II of Orange Nassau to Mary Stuart, the daughter of Charles I.
Mary later pawned the diamond to help fund her brother Charles II's claims to the English throne. The Beau Sancy then found its way to William III of Orange-Nassau before arriving with Frederick I of Prussia in 1701.
It had since remained among descendants of the Prussian royal family until yesterday, when it sold to an anonymous bidder.
"It's extremely rare for a diamond of this importance to come on the market," commented Sotheby's David Bennett.
The sale also featured a brooch, containing a diamond once owned by Bonnie Prince Charlie, which sold for $968,085.