The diamond coveted by royalty for centuries will be auctioned at Sotheby's in Geneva. Beau Sancy had a part in the fluctuating fortunes of Europe's royal families for more than 400 years and currently belongs to Georg Friedrich, Prince of Prussia and head of the former ruling dynasty of the German empire. 　　The 34-carat modified "pear double rose cut" diamond is expected to fetch between two and four million U.S. dollars. And Sotheby's David Bennet says the sale is a major event in the diamond world. [3] 　　David Bennet (Chairman of Sotheby's jewelry department in Europe and the Middle East and co-chairman of Sotheby's Switzerland): "It's extremely rare for a diamond of this importance to come on the market. 　　It's never been out of royal hands, so it's immaculate provenance. It's also a spectacular stone, it weighs 34 carats. It's in all the history books of famous stones." 　　Bennett sold a pink diamond for 46.2 million U.S. dollars in 2010, a record for any jewel at auction. He said estimating the value of a stone like the Beau Sancy was difficult given its rarity. 　　David Bennet: "Of course on the 15th of May in Geneva, [5]we will find out how accurate or not that was. But there's been a lot of interest as we've taken it all around the world; it's been in Hong Kong, New York and Europe. 　　It's been greeted with a lot of admiration wherever it's been." And even though Sotheby's says Queen Elizabeth II has long wanted to own Beau Sancy, it will remain in London only until May 1st, when it will be taken to Geneva ahead of the May 15th sale. And for the first time in its history, the famous gem could even land in the hands of a commoner. (Tara Cleary/ Reuters)