Royal gem fetches $9.6m

A centuries-old diamond passed down through generations of European royalty has fetched 9 million Swiss francs ($A9.62 million) at auction. The 35 carat Beau Sancy diamond was worn by Marie de Medici, Queen consort of Henry IV, at her coronation in 1610.

Five bidders spanning three continents competed for the jewel at a Sotheby's auction, where there was little evidence of global financial woes.

An anonymous telephone bidder purchased the jewel, described by Sotheby's as one of the ''most fascinating and romantic'' gems to come to auction.

''You are buying a historic work of art - you are not buying a diamond,'' said Philipp Herzog von Wurttemberg, chairman of Sotheby's Europe, following the sale.