Although copper mineralization was found by the earliest Spanish explorers of Arizona, the territory was remote, and copper could not be profitably mined and shipped. Early Spanish, Mexican, and American prospectors searched for gold and silver (see Silver mining in Arizona), and ignored copper. It was not until the completion of the Southern Pacific Railroad in 1876 that copper became broadly economic to mine and ship to market.
All copper mining was done by underground methods until the early 20th century. After the Bingham Canyon mine in Utah successfully mined a large low-grade copper deposit from a large open pit, the same technique was applied to Arizona’s porphyry copper deposits. Arizona's first open pit copper mine opened at Ajo in 1917.
The United Verde mine exhausted the rich oxidized ores in 1884, and the mine closed. William A. Clark of Montana visited the district in 1888, bought it, and reopened the mine. The smelter at Clarkdale was built in 1915.
Spaniards mined on a small scale at Ajo as early as 1750. After the Gadsden Purchase brought the southern Arizona into the United States in 1853, Americans reopened the mine in 1855, and shipped high-grade ore to Swansea in Wales. However, the remote desert location made mining generally uneconomic without onsite treatment. The area was mostly idle until the New Cornelia mine opened in 1917 as the first large open-pit mine in Arizona. Mining continued in the district until 1983. The district produced 6.304 billion pounds of copper.
The Morenci mine, owned jointly by Freeport-McMoran and Sumimoto, is the largest copper producer in the state, and regularly contributes about half of Arizona's copper production.
An army scout noted copper mineralization in the Warren district at present-day Bisbee in 1877. Production began in 1880 after a rich discovery of copper oxide on the Copper Queen claim. The success of the Copper Queen mine convinced Phelps Dodge to buy the adjacent Atlantic claim in 1881. Phelps Dodge later bought control of the Copper Queen and adjacent claims.
Although Phelps Dodge was the largest mining company in Bisbee, it was not the only one. The Calumet and Arizona company formed in 1901, and operated the large and profitable mine of the same name adjacent to the Copper Queen. By 1907, the C&A was the fourth-most productive copper mine in Arizona, and ran its own smelter in Douglas, Arizona.
Phelps Dodge started mining the Lavender open pit in the early 1950s. The Lavender pit closed in 1974.
The Copper Queen mine, Bisbee's first working mine, was also its last. Mining stopped in 1975, although the Copper Queen still offers tours.
The Warren district is credited with having produced 7.92 billion pounds (3.59 million mt) of copper. In addition, the district recovered 324 million pounds (147 thousand mt) of lead, 355 million pounds (161 thousand mt) of zinc, 28 million pounds (13 thousand mt) of manganese, 2.79 million ounces (86.8 mt) of gold and 102 million ounces (3177 mt) of silver.
Silver mining started at Globe in 1874. The silver mines shut down in 1877, but the following year copper mining took over.
|Rank||Mine||County||Operator||Source of copper||Capacity (thousands of metric tons)|
|1||Morenci||Greenlee||Freeport-McMoRan||Copper ore, leached||390|
|2||Ray||Pinal||ASARCO||Copper ore, concentrated and leached||170|
|3||Bagdad||Yavapai||Freeport-McMoRan||Copper-molybdenum ore, concentrated and leached||100|
|4||Sierrita||Pima||Freeport-McMoRan||Copper-molybdenum ore, concentrated and leached||100|
|5||Mission Complex||Pima||ASARCO||Copper ore, concentrated||70|
|6||Silver Bell||Pima||ASARCO||Copper ore, leached||22|
|7||Miami||Gila||Freeport-McMoRan||Copper ore, leached||50|
|8||Pinto Valley||Gila||BHP Copper||Copper ore, leached||5|
|9||Miami||Gila||BHP Copper||Copper ore, leached||5|
|* (TBD)||Tohono||Pinal||Cyprus Amax Minerals||Closed|
|* (TBD)||Mineral Park||Mohave||Mercator Minerals||6|
|* (TBD)||Safford||Graham||Freeport-McMoRan||Copper ore, leached||(Opened December 2007)|
In addition, BHP Billiton's Pinto Valley mine in Pinal County restarted copper-molybdenum concentration in late 2007; this portion of its operations had been shut down in 1998.
Freeport-McMoRan has opened its new Safford Mine, eight miles north of the town of Safford in Graham County. The Safford mine, in a large porphyry copper deposit, will be the largest new copper mine put on production in Arizona in more than 30 years.
Other potential new copper mines are the Carlota project (owned by Quadra) in Pinal County and expected to start in 2008, and the Rosemont project (owned by Augusta Resources) in Pima County. Mining of the Resolution deposit in Pinal County, potentially the largest copper mine in Arizona, is stalled pending a proposed land swap with the federal government.