In the United States, copper mining has been a major industry since the rise of the northern Michigan copper district in the 1840s. In 2017, the US produced 1.27 million metric tonnes of copper, worth $8 billion, making it the world's fourth largest copper producer, after Chile, China, and Peru. Copper was produced from 23 mines in the US. Top copper-producing states in 2014 were (in descending order) Arizona, Utah, New Mexico, Nevada, and Montana. Minor production also came from Idaho and Missouri. As of 2014, the US had 45 million tonnes of known remaining reserves of copper, the fifth largest known copper reserves in the world, after Chile, Australia, Peru, and Mexico.Mineral Commodity Summary - U.S. Geological Survey - January 2018

Copper in the US is used mainly in construction (43%) and electric equipment (19%). In 2014, the nation produced 69% of the copper it used, relying on imports from Chile, Canada, Peru, and Mexico for the remaining 31%.

Copper mining activity increased in the early 2000s because of increased price: the price increased from an average of $0.76 per pound for the year 2002, to $3.02 per pound for 2007.D.R. Wilburn, "Exploration review," Mining Engineering, May 2008, p. 47.

A number of byproducts are recovered from American copper mining. In 2013, American copper mining produced 28,500 metric tons of molybdenum, worth about $700–800 million, which was 47% of total US production.Molybdenum US Geological Survey, Minerals Yearbook 2013. In 2014, copper mining produced about 15 metric tons of gold, worth $600 million, which represented 7% of US gold production.Gold US Geological Survey, Commodity Updates, 2015 Other byproducts of the copper extraction process included silver, and minor amounts of rhenium and platinum-group metals. Sulfuric acid is recovered at copper smelters.US Geological Survey, Sulfur, Minerals Yearbook, 2012.

Ore grades

From the start of copper mining in the Michigan copper district, ore has been divided into two classes. The rock with higher copper content was smelter ore, also called direct shipping ore, and required no treatment before going to the smelter. The rock with less copper was called milling ore, or concentrating ore, and required crushing and separation of ore minerals from the waste rock to produce copper concentrate, which was sent to the smelter.

Because metallic minerals have higher specific gravities than most gangue (waste) minerals, concentrating the milling ore was done in various gravity classifiers. The early Michigan copper mines used buddles. Later copper mining used improved gravity-classification machinery, including jigs, vanners, and Wilfley tables.

A revolutionary development in American copper mining took place when mining engineer Daniel Cowan Jackling conceived of mining the huge but low-grade copper ore body at Bingham Canyon, Utah, using steam shovels in a big open pit. Steam shovels had previously been used in the iron mines of the Mesabi Range, in Minnesota, but had not been used in copper mining. Jackling incorporated the Utah Copper Company in 1903, and in 1906 began excavating. From the start, the Bingham Canyon Mine was one of the leading copper-producing mines in the world, and returned a good profit mining ore with less than two percent copper.Horace J. Stevens, The Copper Handbook, v8 (Houghton, Mich: Horace Stevens, 1908) 1377–1381. Mining by open-pit model using large-scale mechanization was copied by other US mines, in Ely, Nevada (1908), Santa Rita, New Mexico (1910), and Ajo, Arizona (1917). The entire output of these mines was low-grade milling ore. The open-pit mining of porphyry copper deposits was adopted worldwide.

In the 1910s and 1920s, copper mills adopted the froth flotation method, which had been developed in Australia. Whereas the old gravity methods of concentration, using jigs and Wilfley tables recovered 60 to 80 percent of the copper in the ore, froth flotation recovered 90 to 95 percent.George J. Young, Elements of Mining, 4th ed. (New York: McGraw-Hill, 1946) 3. The Bingham Canyon mill installed froth flotation in 1918.

Large-scale mining of low-grade orebodies became predominant, and the amount of direct-shipping ore mined fell drastically in the first half of the 20th century, and by 1960, the contribution of direct-shipping ore was insignificant. Improvements in low-cost mining and ore processing allowed the average ore grade of milling ore to decline.

Smelters There are three operating copper smelters in the United States.World copper smelters, US Geological Survey, published 2002, accessed 21 June 2016.

Grupo Mexico, Hayden, Arizona , Grupo Mexico, accessed 18 July 2018. Rio Tinto, Garfield, Utah , Rio Tinto, published 28 February 2017, accessed 18 July 2018. Freeport McMoRan, Miami, Arizona, Freeport McMoRan, published 2 April 2017, accessed 18 July 2018.

The United States is a net exporter of copper ore and copper concentrate. In 2015, out of 1.25 million metric tons of recoverable copper metal extracted from mines, 320,000 tons of copper were exported in the form of ore and concentrate, to be smelted and refined elsewhere.

By state Alabama The Stone Hill mine (also known as the Woods mine) was discovered in 1874, and worked 1874 to 1879, and 1896 to 1899. Production was hampered by poor transportation. The ore is massive and disseminated sulfides in hornblende schist of Precambrian or Paleozoic age. Principal ore minerals are chalcopyrite and sphalerite, which occur with pyrrhotite, pyrite, and quartz. Two other copper prospects, the Johnston prospect and the Smith prospect, are nearby, but it is not known that any copper was produced from them.Gilbert H. Espenshade (1963) Geology of some copper deposits in North Carolina, Virginia, and Alabama, US Geological Survey, Bulletin 1142-I, p.I42-I46.

Alaska

Alaska is not currently a significant copper producer.

Russian explorers discovered copper on the Kasaan Peninsula of Prince of Wales Island in southeastern Alaska about 1865. Mining began in the period 1895–1900, and continued until shortly after World War I. Copper is present as chalcopyrite, occurring with magnetite, pyrite, garnet, epidote, diopside, and hornblende, in replacement deposits in greenstone. Gold and silver were recovered as byproducts.L.A. Warner, E.N. Goddard, and others (1961) Iron and copper deposits of Kasaan Peninsula, Prince of Wales Island, Southeastern Alaska, US Geological Survey, Bulletin 1090.

Copper was discovered at Prince William Sound in 1897. Deposits were associated with pillow basalts altered to greenstone. The basalts are interbedded with slate and greywacke, faulted, and intruded by granitic rocks. The principal mines were the Beatson-Bonanza mine at Latouche and the Ellamar mine, which accounted for 96% of the copper produced. Other mines were the Midas mine near Valdez, the Threeman mine, and the Fidalgo-Alaska mine at Port Fidalgo, Alaska. Mining began in 1900, and continued until 1930. Total production was 96,000 tonnes of copper.Fred H. Moffit and Robert E. Fellows (1950) Copper Deposits of the Prince William Sound District, Alaska, US Geological Survey, Bulletin 963-B.

Historically, the largest copper mining district in Alaska was the Nizina district, the principal mines of which (Erie mine, Jumbo mine, Bonanza mine, Mother Lode mine, and Green Butte mine) were at Kennecott, Alaska, four miles north of McCarthy. The copper is present as chalcocite in veins and irregular replacements in the Triassic Chitistone Limestone. Some silver was also produced as a byproduct.Don J. Miller (1946) Copper Deposits of the Nizina District, Alaska, US Geological Survey, Bulletin 947-F. The mine at Kennecott gave rise to Kennecott Copper Corporation, which outlasted the mine, and is still a major mining company. The deposit was discovered in 1900, and once a railroad connection was built, the mine operated from 1911 to 1938, after which Kennecott became a ghost town. The town is now a National Historic Landmark.

The Pebble Mine is a proposed copper-gold-molybdenum mine. The deposit is a large porphyry copper-gold-molybdenum deposit, and if developed would be a major producer of those metals.

Arizona

Arizona has been a major copper producer since the 19th century. In 2006, Arizona was the leading copper-producing state in the US, producing a record $5 billion worth of copper.Arizona Mining Association: Copper, the star of Arizona , accessed 6 April 2009.

Over 60% of the newly mined copper in the U.S. comes from Arizona. When copper traded for an average of $3.30/pound, copper production generated nearly $5 billion for Arizona's economy in 2006 and $5.5 billion in 2007.

The first mineral to be mined in Arizona was, as in many other regions, gold. Silver was also prominent, in the cities of Tubac and Superior. However, Arizona would most prominently be known for its copper, which would eventually become known as one of Arizona's Five C's or resources.COPPER: THE FOUNDATION OF AMERICA'S 48TH STATE

The first copper strike by an Anglo was by Henry Clifton, in the area now known as Clifton, in 1864. No claim was staked there because of threat of Indian attack. In 1870, Robert Metcalf staked a claim there, then sold controlling interest to Henry and Charles Lesinsky. They later formed the Longfellow Copper Mining Co. in Las Cruces, New Mexico. They set up camp and called it Clifton. Clifton later became one of the largest copper mining communities of Arizona.

This new use of copper resulted in the boom of one of Arizona's greatest resources. By 1910, Arizona produced more copper than any other state in the nation. It would eventually fuel many of its political struggles as well. The Bisbee and Jerome Deportations in 1917 represent how factory workers and factory owners were pitted against each other.Bisbee, Arizona library

At Mule Canyon, south of Tombstone, Arizona, in 1877, a soldier chasing Apache Indians found copper at Bisbee. The Copper Queen Mine and neighboring Atlanta Claim became the Warren District. With the great contribution of the Warren District, Arizona led the nation and still leads it in copper production.

The United Verde copper mine at Jerome, Arizona, was financed by eastern capitalists. However, the rich surface ore soon played out. W. A. Clark, who had obtained his fortune at Butte, purchased 99% of the stock of the United Verde Mine. Ultimately, it yielded copper, silver, and gold totaling $410,000,000. W. A. Clark was the owner of the richest, individually owned copper mine in the world. After the mines closed, Jerome was reborn as an artist community.

Twelve active copper mines in Arizona directly employ nearly 10,000 workers, not including contractors and sub-contractors. Half of Arizona's copper is mined in Morenci. An additional nine copper mines are expected to begin production in the coming years. The Resolution Copper Project, near Superior, is expected to provide 25% of the U.S. demand for copper after it begins production.Arizona Geology: Blogspot

California Copper was first discovered in California in 1840, in Los Angeles County. The mine, at Soledad Township, produced a small amount of copper in 1854.Horace J. Stevens (1909) The Copper Handbook, v.8, Houghton, Mich.: Horace Stevens, p.176.