'Bleu Royal' blue diamond is on the Christie's auction block next week
                                
                                
                                    (Newser) -
                                    Tuesday's the day for the "Bleu Royal," the biggest internally flawless fancy vivid blue diamond ever to go on the auction block. That's when the rare 17.6-carat gem, currently set in a ring, will be up for grabs in Geneva via  Christie's , where it'...