It's a safe bet that most of those surprised with diamond jewelry over the holidays did not pause long, if at all, to consider where their new gemstones came from. "Santa's elves" is a good enough answer for most people, and even those who are aware that some diamonds have been known to come from African war zones may not have given the matter much thought this year. "Conflict diamonds," also known as "blood diamonds," are rough stones mined at gunpoint by slaves and prisoners for the enrichment of those holding the weapons. They were a cause célèbre at the...