The Winston Blue

At 13.22 carats, this piece was actually marketed and sold as an engagement ring. Before 2014, only a handful of blue diamonds weighing between 10 and 12 carats had ever been sold at auction. So, when this 13+ carat monster came across the auction block at Christies in Geneva, it was believed it would bring in at least $21 million. The background of the diamond is not well known, although most experts agree that the diamond likely came from South Africa where most of the worlds blue diamonds originate.