You could probably sell it to just about any gold dealer, as a lot of them sell iridium bars anyway. The tools they have to verify the purity of gold also work for other metals. If not, then they would certainly have connections to find someone who will buy it.

Also, you generally buy/sell on a 5-10% spread from the "spot" market price of the metal, depending on the quanitity you're dealing with. Dealers generally offer a closer price to spot when dealing with larger dollar value amounts of metal.