The diamond Marie de Medici wore when she was crowned queen of France in 1610 has been sold at auction in Geneva for an eye-popping $9.7 million. The 35-carat pear-shaped "Beau Sancy" diamond has been passed down by royal families through the centuries. The buyer is anonymous, reports the BBC. "It's extremely rare for a diamond of this importance to come on the market," said a Sotheby's spokesman. "It's never been out of royal hands, it's of immaculate provenance, and it's in all the history books of famous stones." The diamond was pawned by Mary Stuart to fund the fight by her brother, the future Charles II, for the English throne. It was later the centerpiece in the crown of the first king of Prussia.