n May 2003, Nelson Mandela—former South African president, winner of the Nobel Peace Prize, and hero to millions—sat down at the dinner table of his house in Johannesburg and laid his right hand, palm side down, into a lump of cold dental putty. A team of technicians from the precision-casting division of Harmony Gold Mining Co. was present to supervise, and Mandela chatted amiably with them as they worked, pausing to sip coffee with his free hand.