A rare blue diamond handed down through generations of German royalty sold for a record-breaking $24.3 million at auction Wednesday in London, Christie's said.

The Wittelsbach Diamond, a 35.56 carat cushion-shaped gem, has often had its color and clarity compared to the famed Hope Diamond, now on display at the Smithsonian Institution in Washington.

The rare gem was snapped up by billionaire diamond-dealer Laurence Graff for about $24.3 million, including buyer's premium, Christie's spokeswoman Alexandra Kindermann said.

Kindermann said the price — nearly double its pre-sale estimate — was the most ever paid for a diamond at auction, beating the $16.5 million commanded by a 100-carat diamond at a Swiss auction in 1995.

Christie's said the diamond was purchased by King Philip IV of Spain in 1664 and included in the dowry for his teenage daughter, the Infanta Margarita Teresa. Although she died relatively young, the diamond remained with her husband, Leopold I of Austria, and passed through a succession of heirs.

The gem got the Wittelsbach name after 1722, when Leopold's granddaughter married Charles of Bavaria, a member of the Wittelsbach family.

"Der Blaue Wittelsbacher," as it was then known, made its way through a succession of Bavarian rulers — Maximilian IV Joseph von Wittelsbach, Bavaria's first king, included the diamond in his royal crown. The diamond made its last state appearance in 1918 in the aftermath of World War I. It was offered for auction in 1931, but failed to sell and vanished from the public eye.

"What happened to it after 1931 is a little mysterious — there's been lots of speculation," Christie's spokeswoman Hannah Schmidt said. "But what exactly happened is unknown."

The diamond only resurfaced in 1962, when a jeweler recognized its significance and refused a request to re-cut it.

Auctioneer Francois Curiel said Christie's was thrilled to reach "an historic price for an historic diamond."

Colored diamonds often fetch high prices at auction. Christie's sold a much smaller 13.39-carat blue diamond for $8.9 million in May.