Rare 9.51-carat blue diamond auctions in Geneva

The auction house Christie's will be offering up a magnificent 9.51-carat vivid blue diamond, known as "The Mellon Blue", expected to fetch up to $30 million next week in Geneva. The historic jewel was among a number of prized personal belongings Napoleon Bonaparte had brought with him to Waterloo in 1815.

The stone, set on a ring, once belonged to Rachel Lambert Mellon, better known as Bunny Mellon, an American horticulturalist, philanthropist and art collector. The diamond was last seen publicly in 2014, when it was offered at auction in New York after her death, for more than $32 million.