Italian stone expert Dario Del Bufalo speaks on his 2013 discovery
                                
                                
                                    (Newser) -
                                    Dario Del Bufalo, an Italian expert on ancient stone, was signing copies of his book, Prophyry, about the reddish-purple rock favored by Roman emperors when a man flipped to a page showing a priceless Roman mosaic that had vanished during World War II. "'Oh, Helen, look, that's...