Well, from Wikipedia, it looks like copper wasn't really good for anything, even when they figured out how to smelt it. They didn't really get to weapons till bronze, so most of the copper was used for jewelry to indicate social status while stone tools were still used. I have never played it, but didn't Dark Sun have some kind of no-metal theme? Otherwise you could hit up the social angle with like Houses of the Blooded, especially if you made Copper magical.