According to Phoenix-based Freeport-McMoRan's (FCX) second-quarter earnings report, it operates seven open-pit copper mines in North America, many of which also produce molybdenum, gold and silver. All but one of its North American copper mines is wholly owned, and Freeport-McMoRan holds 72% of the joint venture on the last one. I like this exposure to gold and silver because it adds another dimension to the company's asset portfolio through diversification.