Rare diamond up for auction

LONDON — An unusually cut blue diamond with a royal history could fetch as much as $13 million when it goes under the hammer at Christie's on Wednesday.

Blue diamonds are exceedingly rare, and the 35.56 carat Wittelsbach Diamond has often had its color and clarity compared to the famed Hope Diamond, which is on display at the Smithsonian Institution in Washington.

Though somewhat smaller than the Hope Diamond, the Wittelsbach Diamond was a favorite of European rulers for centuries. King Philip IV of Spain purchased the stone in 1664 and made it part of the dowry for his teenage daughter, the Infanta Margarita Teresa. Though she died relatively young, the diamond remained with her husband, Leopold I of Austria, and passed through a succesion of his heirs.

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

It stayed with the family until some time after 1918, when it was lost in the aftermath of World War I. Christie's first auctioned the Wittelsbach diamond in 1931, after which it disappeared from the public eye.

The large diamond resurfaced in the 1960s, when a jeweler recognized its historical significance and refused to re-cut it.

Francois Curiel, Christie's international head of jewelry, described the diamond as "museum quality." It is the centerpiece of Christie's London jewelry sale.

Colored diamonds command a high price at auction. Christie's sold a much smaller 13.39 carat blue diamond for $8.9 million in May.