Sierrita Copper Mine, Arizona

The Sierrita Copper Mine is the southernmost of three major open pit copper mines south of Tucson. It is a large open pit more than a mile wide, and 1,400 feet deep, surrounded by piles of overburden and a large tailings pond. Operated for years by the Cyprus Mineral Company, it was purchased by Phelps Dodge in 1999, which was acquired by Freeport McMoRan in 2007. Copper, and a fair amount of molybdenum have been mined here. In 2015, Freeport McMoRan announced its intention to close the mine due to depressed copper prices.