Copper extraction
Copper extraction is the multi-stage process of obtaining copper from its ores. The conversion of copper ores consists of a series of physical, chemical, and electrochemical processes. Methods have evolved and vary with country depending on the ore source, local environmental regulations, and other factors. The copper smelters with the highest production capacity lie in China, Chile, India, Germany, Japan, Peru and Russia. China alone has over half of the world's production capacity and is also the world's largest consumer of refined copper.
Precious metals and sulfuric acid are often valuable by-products of copper refining. Arsenic is the main type of impurity found in copper concentrates to enter smelting facilities. There has been an increase in arsenic in copper concentrates over the years since shallow, low-arsenic copper deposits have been progressively depleted.
History
Prehistory
The Old Copper Complex in North America has been radiometrically dated to around 6500 BCE, at least—making it one of the oldest known examples of copper extraction in the world. The earliest evidence of the cold-hammering of native copper comes from the excavation at Çayönü Tepesi in eastern Anatolia, which dates between 7200 and 6600 BCE. Among the various items considered to be votive or amulets, there was one that looked like a fishhook and one like an awl. Another find, at Shanidar Cave in Mergasur, Iraq, contained copper beads, and dates back to 8,700 BCE.One of the world's oldest known copper mines, as opposed to usage of surface deposits, is at Timna Valley, Israel, and has been used since the fourth millennium BC, with surface deposit usage occurring in the fifth and sixth millennium.
The Pločnik archaeological site in southeastern Europe contains the oldest securely dated evidence of copper making at high temperature, from 5,000 BCE. The find in June 2010 extends for an additional 500 years, dated to 5th millennium BCE, representing the earlier record of copper smelting from Rudna Glava.
The earliest copper work in the Atacama Desert and the Andean world as whole dates to 1432–1132 BC. Ice core studies in Bolivia suggest copper smelting may have begun as early as 700 BC, over 2700 years ago. Various sites of Pre-Hispanic mines and metallurgical workshops have been identified in Atacama Desert including those with remnants of chisels, casting waste and workshop debris. Tin broze, arsenical bronze, and arsenical copper were valuable goods produced in the Inca Empire. About 74 km northeast of the Chilean city of Copiapó in Viña del Cerro the Incas had one of their largest mining and metallurgy centres at Qullasuyu. There is evidence of gold, silver and copper metallurgy at the site, including the production of bronze. When conquistador Diego de Almagro traversed the Atacama Desert in 1536 his men readilly obtained copper horseshoes for their horses.
Copper smelting technology gave rise to the Copper Age, aka Chalcolithic Age, and then the Bronze Age. The Bronze Age would not have been possible without the development of smelting technology.
19th century
The introduction of reverberatory furnaces to Chile around 1830 by Charles Saint Lambert revolutionized Chilean copper mining. In addition to this there was improvements of transport caused by the development of railroads and steam navigation. Prospector José Tomás Urmeneta discovered rich orebodies at Tamaya in 1850, a site that became one of Chile's main copper mines. All of this made Chile supply 18% of the copper produced worldwide in the 19th century and the country was from the 1850s to the 1870s the world's top producer. In some years Chile's copper production made up about 60% of the worlds output and its export tariff made up more than half the state's income.Lambert's success in modernising the Chilean copper industry during the second quarter of the nineteenth century is thought to have sowed the seeds for the later demise of his own copper smelting business in Swansea.
By the late 19th century the Chilean mining industry once again lagged behind technological developments contributing to the drop of its share of the world production to 5–6% in the 1890s and similar shares remained in the 1900s and 1910s reaching a low of 4.3% in 1914. Up to the 1940s and 1950s there was also a notable lack of major copper exploration efforts by large mining companies that relied on purchasing prospects already known from the activity of small-scale miners and pirquineros.
Smelting
Until the latter half of the 20th century, smelting sulfide ores was almost the sole means of producing copper metal from mined ores. As of 2002, 80% of global primary copper production was from copper–iron–sulfur minerals, and the vast majority of these were treated by smelting.Copper was initially recovered from sulfide ores by directly smelting the ore in a furnace. The smelters were initially located near the mines to minimize the cost of transport. This avoided the prohibitive costs of transporting the waste minerals and the sulfur and iron present in the copper-containing minerals. However, as the concentration of copper in the ore bodies decreased, the energy costs of smelting the whole ore also became prohibitive, and it became necessary to concentrate the ores first.
Initial concentration techniques included hand-sorting and gravity concentration. These resulted in high losses of copper. Consequently, the development of the froth flotation process was a major step forward in mineral processing. The modern froth flotation process was independently invented in the early 1900s in Australia by C.V Potter and around the same time by G. D. Delprat. It made the development of the giant Bingham Canyon mine in Utah possible.
In the twentieth century, most ores were concentrated before smelting. Smelting was initially undertaken using sinter plants and blast furnaces, or with roasters and reverberatory furnaces. Roasting and reverberatory furnace smelting dominated primary copper production until the 1960s.
Late 20th century trends
In the 1960s and 1970s large copper mining operations by U.S. companies were nationalized in many of the main copper producing countries. Thus by the 1980s state owned enterprises overtook the dominant role U.S. companies like Anaconda Copper and Kennecott had had until then. In the late 1970s and early 1980s various oil companies like ARCO, Exxon and Standard Oil Company expanded into copper mining for a few years before selling their copper assets. Reportedly gains were not as high as anticipated. Investments in copper mining concentrated in Chile in the 1980s and 1990s given that copper mining in other countries faced problems like political instability, increased environmental requirements or overall disinterest in foreign investment in a nationalized mining industry.21st century
In the 2013-2023 period the copper smelting capacity in China and Zambia have increased while the capacity in Chile and the United States have decreased. China has by far the largest capacity for copper smelting with over half of the world's total. Besides the previously mentioned countries other countries where there is a significant installed cathode production capacity of the world's total as of 2023 are Japan, Russia, Poland and Bulgaria.Since the 1990s no new copper smelter have been built in Chile. Following the 2022 closure of Fundición Ventanas in central Chile there have been a public discussion on building a new large copper smelter in Chile. Antofagasta Region or Atacama Region has been proposed by Chilean industry scholars as viable replacements. Others have argued for keeping smelting in Valparaíso Region given the existence of nearby mines. While some argue the replacement plant should be near the coast, inland Chuquicamata and El Salvador have also been proposed as alternatives. The president of the National Mining Society, Diego Hernández, estimates the construction period for a new smelter plant to be 5 to 7 years. A 2024 study identified Antofagasta Region as the best place for a new copper smelter given logistical advantages and an existing and expandable supply of copper concentrate from nearby mines.
The Guixi Smelter in inland southeastern China is the world's largest copper smelter by capacity. In 2015 it had an annual production capacity of 900,000 tons of copper.
Concentration (beneficiation)
The average grade of copper ores in the 21st century is below 0.6% copper, with a proportion of economic ore minerals being less than 2% of the total volume of the ore rock. Thus, all mining operations, the ore must usually be beneficiated. The concentrate is typically sold to distant smelters, although some large mines have smelters located nearby. Such colocation of mines and smelters was more typical in the 19th and early 20th centuries, when smaller smelters could be economic. The subsequent processing techniques depend on the nature of the ore.In the usual case when it is primarily sulfide copper minerals, the ore is treated by comminution, where the rock is crushed to produce small particles consisting of individual mineral phases. These particles are then ready to be separated to remove gangue using froth flotation.