View source for Engineering:Copper extraction

{{Short description|Process of extracting copper from the ground}}
[[File:Chino copper mine.jpg|right|thumb|The Chino open-pit copper mine in New Mexico]]
[[File:Chalcopyrite perou.jpg|right|thumb|[[Chemistry:Chalcopyrite|Chalcopyrite]] specimen from Huarón mine, Peru]]

'''Copper extraction''' refers to the methods used to obtain [[Chemistry:Copper|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 [[Social:Environmental law|environmental regulations]], and other factors.<ref name=Ullm/>

==History==
[[File:TamarackMiners CopperCountryMI.jpg|thumb|Miners at the Tamarack mine in Copper Country, in 1905]]
The Old Copper Complex in North America has been radiometrically dated to 9500 BP—i.e., about 7480 BCE—making it one of the oldest known examples of copper extraction in the world.<ref>{{cite news |last1=Malakof |first1=David |title=Ancient Native Americans were among the world's first coppersmiths |url=https://www.science.org/content/article/ancient-native-americans-were-among-world-s-first-coppersmiths |access-date=6 June 2022 |publisher=Science |date=19 March 2021}}</ref> The earliest evidence of the cold-hammering of native copper comes from the excavation at Çayönü Tepesi in eastern [[Earth:Anatolia|Anatolia]], which dates between 7200 to 6600 BCE.<ref>{{cite journal|title=Beginnings of Village-Farming Communities in Southeastern Turkey|journal=Proc Natl Acad Sci U S A |volume=68 |issue=6 |pages=1236–1240|year=1971|pmid=16591930|pmc=389161 |first1=Robert J. |last1=Braidwood |first2=Halet |last2=Çambel |first3=Charles L. |last3=Redman |first4=Patty Jo |last4=Watson |doi=10.1073/pnas.68.6.1236 |bibcode=1971PNAS...68.1236B |doi-access=free}}</ref> 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 [[Biology:Shanidar Cave|Shanidar Cave]] in Mergasur, Iraq, contained copper beads, and dates back to 8,700 BCE.<ref>{{cite book |url=http://www.tamupress.com/product/Proto-Neolithic-Cemetery-in-Shanidar-Cave,78.aspx|title=The Proto-neolithic Cemetery in Shanidar Cave|year=2004|author1=R.S. Solecki|author2=R.L. Solecki |author3=A.P. Agelarakis |page=53|publisher=Texas A&M University Press|isbn=978-1585442720}}</ref>

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.<ref>{{cite book |url=https://books.google.com/books?id=zmvNogJO2ZgC&q=timna+valley+mines&pg=PA583 |title=A Dictionary of Archaeology |publisher=John Wiley & Sons |first=Ian |last=Shaw |pages=582–583|isbn=978-0631235835 |year=2002 }}</ref><ref>{{cite book |url=https://archive.org/details/lifeinbiblicalis0000king |url-access=registration |quote=timna millennium. |title=Life In Biblical Israel |publisher=Westminster John Knox Press |first1=PJ |last1=King |first2=LE |last2=Stager |page=[https://archive.org/details/lifeinbiblicalis0000king/page/165 165]|isbn=978-0664221485 |year=2001}}</ref>

The Pločnik archaeological site in southeastern Europe (Serbia) contains the oldest securely dated{{dubious|see Talk page|date=February 2016}} 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 (Serbia).<ref>{{cite web |title=Serbian site may have hosted first copper makers |date=July 17, 2010 |work=ScienceNews |url=http://www.sciencenews.org/view/generic/id/60563/description/Serbian_site_may_have_hosted_first_copper_makers |access-date=January 3, 2013 |archive-date=May 8, 2013 |archive-url=https://web.archive.org/web/20130508005006/http://www.sciencenews.org/view/generic/id/60563/description/Serbian_site_may_have_hosted_first_copper_makers |url-status=dead }}</ref>

===Smelting===
Until the latter half of the 20th century, [[Engineering:Smelting|smelting]] sulfide ores was almost the sole means of producing copper metal from mined ores (''primary'' copper production). 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.<ref name="Davenport">W G Davenport, M King, M Schlesinger and A K Biswas, ''Extractive Metallurgy of Copper, Fourth Edition'' (Elsevier Science Limited: Kidlington, Oxford, England, 2002).</ref>

Copper was initially recovered from sulfide ores by directly smelting the ore in a furnace.<ref>Robert Raymond, Out of the Fiery Furnace, The MacMillan Company of Australia Pty Ltd, Melbourne, 1984.</ref> 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<ref name="Gill32">C B Gill, ''Non-ferrous Extractive Metallurgy'' (John Wiley & Sons, New York, 1980) p. 32</ref> and gravity concentration. These resulted in high losses of copper. Consequently, the development of the [[Chemistry:Froth flotation|froth flotation]] process was a major step forward in mineral processing.<ref>Robert Raymond (1984) Out of the Fiery Furnace, The MacMillan Company of Australia Pty Ltd, Melbourne, pp. 233–235, {{ISBN|027100441X}}.</ref> It made the development of the giant Bingham Canyon mine in Utah possible.<ref>"BP Minerals completes US$400 million modernization at Bingham Canyon," ''Mining Engineering'', November 1988, 1017–1020.</ref>

In the twentieth century, most ores were concentrated before smelting. Smelting was initially undertaken using [[Engineering:Sinter plant|sinter plant]]s and [[Engineering:Blast furnace|blast furnace]]s,<ref>S A Bradford (1989) "The historical development of copper smelting in British Columbia," in: ''All that Glitters: Readings in Historical Metallurgy'', Ed. Michael L. Wayman, The Canadian Institute of Mining and Metallurgy: Montreal, pp. 162–165, {{ISBN|0919086241}}.</ref> or with roasters and reverberatory furnaces.<ref>E Kossatz and P J Mackey (1989) "The first copper smelter in Canada," in: ''All that Glitters: Readings in Historical Metallurgy'', Ed. Michael L. Wayman, The Canadian Institute of Mining and Metallurgy: Montreal, pp. 160–161, {{ISBN|0919086241}}.</ref> Roasting and reverberatory furnace smelting dominated primary copper production until the 1960s.<ref name="Davenport"/>

Copper smelting technology gave rise to the Copper Age, aka Chalcolithic Age, and then the [[History:Bronze Age|Bronze Age]]. The Bronze Age would not have been possible without the development of smelting technology.

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.<ref>{{cite web |url=http://www.austehc.unimelb.edu.au/guides/mine/historicalnote.htm|title=Historical Note |access-date=2007-12-30 |publisher=Minerals Separation Ltd}}</ref>

==Concentration (beneficiation)==
[[file:Evolution minerai cuivre.svg|thumb|lang=en|upright=1.35|The decreasing concentration of copper in ores now requires pre-treatment of ores.|link=File:Evolution_minerai_cuivre.svg]]

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 [[Earth:Ore|ore]] must usually be [[Engineering:Beneficiation|beneficiated]] (concentrated). The concentrate is typically sold to distant [[Engineering:Smelting|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 (such as [[Chemistry:Chalcopyrite|chalcopyrite]], FeCuS<sub>2</sub>), the ore is treated by ''[[Engineering:Comminution|comminution]]'', where the rock is crushed to produce small particles (<100 μm) consisting of individual mineral phases. These particles are then ready to be separated to remove gangue (silicate rocks residues) using froth flotation.<ref name=Ullm>{{cite book|doi=10.1002/14356007.a07_471|chapter=Copper |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2001 |last1=Lossin |first1=Adalbert |isbn=3527306730 }}</ref>

===Froth flotation===
[[File:FlotationFalconbridgeOnt.jpg|thumb|left|Froth flotation cells to concentrate copper and nickel sulfide minerals, Falconbridge, Ontario.]]
[[File:Prominenthill-flotation.jpg|thumb|left|Copper sulfide loaded air bubbles on a Jameson Cell at the flotation plant of the Prominent Hill mine in South Australia]]

In froth flotation, the crushed ore is wetted, suspended in a slurry, and mixed with reagents that render the sulfide particles [[Chemistry:Hydrophobic|hydrophobic]]. Typical reagents ("collectors") include potassium ethylxanthate and sodium ethylxanthate, but dithiophosphates and dithiocarbamates are also used. The slurry is introduced to a water-filled aeration tank containing a [[Biology:Surfactant|surfactant]] such as [[Chemistry:4-Methyl-2-pentanol|methylisobutyl carbinol]] (MIBC). Air is constantly forced through the slurry. The air bubbles attach to the hydrophobic copper sulfide particles, which are conveyed to the surface where the froth is skimmed off. These skimmings are generally subjected to a cleaner-scavenger cell to remove excess silicates and to remove other sulfide minerals that can deleteriously impact the concentrate quality (typically, [[Chemistry:Galena|galena]]), and the final concentrate sent for smelting. The rock that has not floated off in the flotation cell is either discarded as [[Engineering:Tailings|tailings]] or further processed to extract other metals such as lead (from galena) and zinc (from [[Chemistry:Sphalerite|sphalerite]]), should they exist. A variety of measures are taken to improve the efficiency of the froth flotation. [[Chemistry:Lime (material)|Lime]] is used to raise the [[Chemistry:PH|pH]] of the water bath, causing the collector to bond more efficiently to the copper sulfides. The process can produce a concentrates with 27–29% and 37–40% copper contents from [[Chemistry:Chalcopyrite|chalcopyrite]] and [[Chemistry:Chalcocite|chalcocite]], respectively.

===Hydrometallurgy===
[[File:Cu(Salox)2.png|thumb|left|upright|In some hydrometallurgical schemes, copper(II) is extracted from aqueous solution as by complexation to [[Chemistry:Salicylaldoxime|salicylaldoxime]].]]

Oxidised copper ores include carbonates such as [[Chemistry:Azurite|azurite]] and [[Chemistry:Malachite|malachite]], the silicate [[Chemistry:Chrysocolla|chrysocolla]], and sulfates such as [[Chemistry:Atacamite|atacamite]]. In some cases, sulfide ores are allowed to degrade to oxides. Such ores are amenable to hydrometallurgy. Specifically, such oxide ores are usually extracted into aqueous [[Chemistry:Sulfuric acid|sulfuric acid]], usually in a [[Engineering:Heap leaching|heap leaching]] or [[Engineering:Dump leaching|dump leaching]]. The resulting pregnant leach solution is purified by solvent extraction (SX). It is treated with an organic solvent and an organic chelators. The chelators bind the copper ions (and no other ions, ideally), the resulting complexes dissolve in the organic phase. This organic solvent is evaporated, leaving a residue of the copper complexes. The copper ions are liberated from the residue with sulfuric acid. The barred (denuded) sulfuric acid recycled back on to the heaps. The organic ligands are recovered and recycled as well. Alternatively, the copper can be precipitated out of the pregnant solution by contacting it with scrap iron; a process called [[Engineering:Cementation (metallurgy)|cementation]]. Cement copper is normally less pure than SX-EW copper.<ref>{{cite journal |title=Co-extraction of Cations and Anions in Base Metal Recovery |year=2007 |last1=Tasker |first1=Peter A. |last2=Tong |first2=Christine C. |last3=Westra |first3=Arjan N. |journal=Coordination Chemistry Reviews |volume=251 |issue=13–14 |pages=1868–1877 |doi=10.1016/j.ccr.2007.03.014}}</ref>

===Specialized ores===
[[File:Chalcocite-271692.jpg|thumb|A specimen of the mineral chalcocite from the Geevor Mine, Cornwall.]]
Secondary sulfides—those formed by [[Earth:Supergene (geology)|supergene]] secondary enrichment—are resistant (''[[Chemistry:Refractory|refractory]]'') to sulfuric leaching.<ref>{{Cite journal |last=Petersen |first=Jochen |date=October 2016 |title=Heap leaching as a key technology for recovery of values from low-grade ores – A brief overview |journal=Hydrometallurgy |volume=165 |pages=206–212 |doi=10.1016/j.hydromet.2015.09.001}}</ref> Secondary copper sulfides are dominated by the mineral chalcocite; a mineral formed from primary sulfides, like [[Chemistry:Chalcopyrite|chalcopyrite]], that undergo chemical processes such as oxidation or reduction.<ref>{{Cite journal |last1=Wu |first1=Biao |last2=Yang |first2=Xinlong |last3=Wen |first3=Jiankang |last4=Wang |first4=Dianzuo |date=2019-11-05 |title=Semiconductor-Microbial Mechanism of Selective Dissolution of Chalcocite in Bioleaching |journal=ACS Omega |volume=4 |issue=19 |pages=18279–18288 |pmc=6844112 |pmid=31720528 |doi=10.1021/acsomega.9b02294 |doi-access=free |issn=2470-1343}}</ref> Typically, secondary sulfide ores are concentrated using froth flotation.<ref>{{Cite journal |last1=Rahman |first1=Reza M. |last2=Ata |first2=Seher |last3=Jameson |first3=Graeme J. |date=November 2013 |title=Froth recovery measurements in an industrial flotation cell |journal=Minerals Engineering |volume=53 |pages=193–202 |doi=10.1016/j.mineng.2013.08.003 |issn=0892-6875}}</ref> Other extraction processes like leaching are effectively used for the extraction of secondary copper sulfides, but as demand for copper rises, extraction processes tailored for low-grade ores are required, due to the depletion of copper resources.<ref>{{Cite journal |last1=Yu |first1=Shichao |last2=Liao |first2=Rui |last3=Yang |first3=Baojun |last4=Fang |first4=Chaojun |last5=Wang |first5=Zhentang |last6=Liu |first6=Yuling |last7=Wu |first7=Baiqiang |last8=Wang |first8=Jun |last9=Qiu |first9=Guanzhou |date=January 2022 |title=Chalcocite (bio)hydrometallurgy—current state, mechanism, and future directions: A review |journal=Chinese Journal of Chemical Engineering |volume=41 |pages=109–120 |doi=10.1016/j.cjche.2021.12.014 |s2cid=245562646 |issn=1004-9541}}</ref> Processes including in situ, dump, and heap leaching are cost-effective methods that are suitable for extracting copper from low-grade ores.<ref>{{Cite journal |last=Watling |first=H. R. |date=October 2006 |title=The bioleaching of sulphide minerals with emphasis on copper sulphides — A review |journal=Hydrometallurgy |volume=84 |issue=1 |pages=81–108 |doi=10.1016/j.hydromet.2006.05.001 |issn=0304-386X}}</ref>

Extraction processes for secondary copper sulfides and low-grade ores includes the process of heap bioleaching. Heap bioleaching presents a cost efficient extraction method that requires a less intensive energy input resulting in a higher profit.<ref name="Panda-2015">{{Cite journal |last1=Panda |first1=Sandeep |last2=Akcil |first2=Ata |last3=Pradhan |first3=Nilotpala |last4=Deveci |first4=Haci |date=November 2015 |title=Current scenario of chalcopyrite bioleaching: A review on the recent advances to its heap-leach technology |journal=Bioresource Technology |volume=196 |pages=694–706 |doi=10.1016/j.biortech.2015.08.064 |pmid=26318845 |s2cid=2254790 |issn=0960-8524}}</ref> This extraction process can be applied to large quantities of low-grade ores, at a lower capital cost with minimal environmental impact.<ref name="Panda-2015"/><ref>{{Cite journal |last=Brierley |first=C. L. |date=December 2008 |title=How will biomining be applied in future? |journal=Transactions of Nonferrous Metals Society of China |volume=18 |issue=6 |pages=1302–1310 |doi=10.1016/S1003-6326(09)60002-9 |issn=1003-6326}}</ref>

Generally, direct [[Chemistry:Froth flotation|froth flotation]] is not used to concentrate copper oxide ores, as a result of the largely ionic and hydrophilic structure of the copper oxide mineral surface.<ref name="Feng-2022">{{Cite journal |last1=Feng |first1=Qicheng |last2=Yang |first2=Wenhang |last3=Wen |first3=Shuming |last4=Wang |first4=Han |last5=Zhao |first5=Wenjuan |last6=Han |first6=Guang |date=November 2022 |title=Flotation of copper oxide minerals: A review |journal=International Journal of Mining Science and Technology |volume=32 |issue=6 |pages=1351–1364 |doi=10.1016/j.ijmst.2022.09.011 |s2cid=253788625 |issn=2095-2686|doi-access=free }}</ref> Copper oxide ores are typically treated via chelating-reagent flotation and fatty-acid flotation, which use organic reagents to ensure adsorption onto the mineral surface through the formation of hydrophobic compounds on the mineral surface.<ref name="Feng-2022"/><ref>{{Cite journal |last1=Fuerstenau |first1=D. W. |last2=Herrera-Urbina |first2=R. |last3=McGlashan |first3=D. W. |date=February 2000 |title=Studies on the applicability of chelating agents as universal collectors for copper minerals |journal=International Journal of Mineral Processing |volume=58 |issue=1 |pages=15–33 |doi=10.1016/S0301-7516(99)00058-7 |issn=0301-7516}}</ref>

Some supergene sulfide deposits can be leached using a [[Biology:Bacterial oxidation|bacterial oxidation]] heap leach process to oxidize the sulfides to sulfuric acid, which also allows for simultaneous leaching with sulfuric acid to produce a [[Chemistry:Copper sulfate|copper sulfate]] solution.<ref>{{Cite journal |last1=Kariuki |first1=Stephen |last2=Moore |first2=Cory |last3=McDonald |first3=Andrew M. |date=March 2009 |title=Chlorate-based oxidative hydrometallurgical extraction of copper and zinc from copper concentrate sulfide ores using mild acidic conditions |journal=Hydrometallurgy |volume=96 |issue=1 |pages=72–76 |doi=10.1016/j.hydromet.2008.08.008 |issn=0304-386X}}</ref><ref>{{Cite journal |last1=Robertson |first1=S.W. |last2=Van Staden |first2=P.J. |last3=Seyedbagheri |first3=A. |date=December 2012 |title=Advances in high-temperature heap leaching of refractory copper sulphide ores |url=http://www.saimm.co.za/Journal/v112n12p1045.pdf |journal=Journal of the Southern African Institute of Mining and Metallurgy |volume=112 |issue=12 |pages=1045–1050 |via=ResearchGate}}</ref> For oxide ores, [[Engineering:Solvent extraction and electrowinning|solvent extraction and electrowinning]] technologies are used to recover the copper from the [[Engineering:Pregnant leach solution|pregnant leach solution]].<ref name="Ochromowicz-2008">{{Cite journal |last1=Ochromowicz |first1=Katarzyna |last2=Chmielewski |first2=Tomasz |date=January 2008 |title=Growing Role of Solvent Extraction in Copper Ores Processing |pages=29–36 |url=https://www.researchgate.net/publication/228679628 |journal=Fizykochemiczne Problemy Mineralurgii |volume=42}}</ref> To ensure the best recovery of copper, it is important to acknowledge the effect copper dissolution, acid consumption, and gangue mineral composition has on the efficacy of extraction.<ref name="Ochromowicz-2008" />

Supergene sulfide ores rich in native copper are refractory to treatment with sulfuric acid leaching on all practicable time scales, and the dense metal particles do not react with froth flotation media. Typically, if native copper is a minor part of a supergene profile it will not be recovered and will report to the [[Engineering:Tailings|tailings]]. When rich enough, native copper ore bodies may be treated to recover the contained copper by [[Chemistry:Gravity separation|gravity separation]]. Often, the nature of the gangue is important, as clay-rich native copper ores prove difficult to liberate. This is because clay minerals interact with flotation reagents used in extraction processes, that are then consumed, which results in minimal recovery of a high grade copper concentrate.<ref>{{Cite journal |last1=Han |first1=Baisui |last2=Altansukh |first2=Batnasan |last3=Haga |first3=Kazutoshi |last4=Stevanović |first4=Zoran |last5=Jonović |first5=Radojka |last6=Avramović |first6=Ljiljana |last7=Urosević |first7=Daniela |last8=Takasaki |first8=Yasushi |last9=Masuda |first9=Nobuyuki |last10=Ishiyama |first10=Daizo |last11=Shibayama |first11=Atsushi |date=2018-06-15 |title=Development of copper recovery process from flotation tailings by a combined method of high‒pressure leaching‒solvent extraction |journal=Journal of Hazardous Materials |volume=352 |pages=192–203 |doi=10.1016/j.jhazmat.2018.03.014 |pmid=29609151 |s2cid=4879400 |issn=0304-3894|doi-access=free }}</ref>

==Roasting==
The roasting process is generally undertaken in combination with reverberatory furnaces. In the roaster, the copper concentrate is partially oxidised to produce "calcine". [[Chemistry:Sulfur dioxide|Sulfur dioxide]] is liberated. The [[Chemistry:Stoichiometry|stoichiometry]] of the reaction is:
:{{chem2|CuFeS2  +  3 O2  ->  2 FeO  +  2 CuS  +  2 SO2}}

Roasting generally leaves more sulfur in the calcined product (15% in the case of the roaster at Mount Isa Mines<ref>B V Borgelt, G E Casley and J Pritchard (1974) "Fluid Bed Roasting at Mount Isa," ''The Aus. I.M.M. North West Queensland Branch, Regional Meeting, August 1974''. The Australasian Institute of Mining and Metallurgy: Melbourne, pp. 123–130.</ref>) than a sinter plant leaves in the sintered product (about 7% in the case of the Electrolytic Refining and Smelting smelter<ref>P J Wand (1980) "Copper smelting at Electrolytic Refining and Smelting Company of Australia Ltd., Port Kembla, N.S.W.", in: '' Mining and Metallurgical Practices in Australasia: The Sir Maurice Mawby Memorial Volume'', Ed J T Woodcock. The Australasian Institute of Mining and Metallurgy: Melbourne. pp. 335–340.</ref>).

As of 2005, roasting is no longer common in copper concentrate treatment because its combination with reverberatory furnaces is not energy efficient and the SO<sub>2</sub> concentration in the roaster offgas is too dilute for cost-effective capture. Direct smelting is now favored, and uses the following smelting technologies: [[Chemistry:Flash smelting|flash smelting]], Isasmelt, Noranda, Mitsubishi or El Teniente furnaces.<ref name="Davenport"/>

===Smelting===
[[file:Evolution copper smelting.svg|thumb|upright=1.35 |Replacement of reverberatory furnace smelting by flash smelting, related to the number of copper smelters using this technology. |link=File:Evolution_copper_smelting.svg%3Flang=en]]
[[File:Inco flash smelting furnace.png|thumb|Flash smelting furnace from Inco.]]
The initial melting of the material to be smelted is usually referred to as the ''[[Engineering:Smelting#Copper and bronze|smelting]]'' or ''matte smelting'' stage. It can be undertaken in a variety of furnaces, including the largely obsolete [[Engineering:Blast furnace|blast furnace]]s and reverberatory furnaces, as well as [[Chemistry:Flash smelting|flash furnaces]], Isasmelt furnaces, etc. The product of this smelting stage is a mixture of copper, iron and sulfur that is enriched in copper, which is called ''[[Engineering:Matte (metallurgy)|matte]]'' or ''copper matte''.<ref name="Davenport"/> The term ''matte grade'' is normally used to refer to the copper content of the matte.<ref name="Smelting">W G Davenport, M King, M Schlesinger and A K Biswas, ''Extractive Metallurgy of Copper, Fourth Edition'' (Elsevier Science Limited: Kidlington, Oxford, England, 2002), pp. 57–72.</ref>

The purpose of the matte smelting stage is to eliminate as much of the unwanted iron, sulfur and ''gangue'' minerals (such as silica, magnesia, alumina and limestone) as possible, while minimizing the loss of copper.<ref name="Davenport"/> This is achieved by reacting iron sulfides with oxygen (in air or oxygen enriched air) to produce iron oxides (mainly as FeO, but with some [[Chemistry:Magnetite|magnetite]] (Fe<sub>3</sub>O<sub>4</sub>)) and [[Chemistry:Sulfur dioxide|sulfur dioxide]].<ref name="Smelting"/>

Copper sulfide and iron oxide can mix, but when sufficient silica is added, a separate [[Chemistry:Slag|slag]] layer is formed.<ref name="Hayes173">P C Hayes, ''Process Principles in Minerals and Materials Production'' (Hayes Publishing Company: Brisbane, 1993), pp. 173–179.</ref> Adding silica also reduces the melting point (or, more properly, the [[Physics:Liquidus|liquidus]] temperature) of the slag, meaning that the smelting process can be operated at a lower temperature.<ref name="Hayes173"/>

The slag forming reaction is:

:FeO + SiO<sub>2</sub> → FeO.SiO<sub>2</sub><ref name="Smelting"/>

Slag is less dense than matte, so it forms a layer that floats on top of the matte.<ref>C B Gill, ''Non-ferrous Extractive Metallurgy'' (John Wiley & Sons, New York, 1980) p. 19</ref>

Copper can be lost from the matte in three ways: as cuprous oxide (Cu<sub>2</sub>O) dissolved in the slag,<ref>R Altman and H H Kellogg, "Solubility of copper in silica-saturated iron silicate slag," ''Transactions of the [[Organization:Institution of Mining and Metallurgy|Institution of Mining and Metallurgy]] (Section C: Mineral Processing and Extractive Metallurgy),'' '''81''', September 1972, C163–C175.</ref> as sulfide copper dissolved in the slag<ref name="Nagamori">{{cite journal |author=M. Nagamori|doi=10.1007/BF02644646|title=Metal loss to slag: Part I. Sulfidic and oxidic dissolution of copper in fayalite slag from low grade matte|year=1974 |journal=Metallurgical Transactions|volume=5|issue=3 |pages=531–538|bibcode=1974MT......5..531N |s2cid=135507603}}</ref> or as tiny droplets (or ''prills'') of matte suspended in the slag.<ref>A Yazawa and S Nakazawa, "Evaluation of non-equilibrium minor components in pyrometallurgy," in: ''EPD Congress 1998'', Ed. B Mishra (The Minerals, Metals and Materials Society: Warrendale, Pennsylvania, 1998), pp. 641–655.</ref><ref name="Elliott">B J Elliott, J B See, and W J Rankin, "Effect of slag composition on copper losses to silica-saturated iron silicate slags," ''Transactions of the Institution of Mining and Metallurgy (Section C: Mineral Processing and Extractive Metallurgy),'' September 1978, C–C211.</ref>

The amount of copper lost as oxide copper increases as the oxygen potential of the slag increases.<ref name="Elliott"/> The oxygen potential generally increases as the copper content of the matte is increased.<ref>{{cite journal|first=J |last=Matousek |title=Oxygen potentials of copper smelting slags|journal=Canadian Metallurgical Quarterly|volume=32|issue=2|year=1993|pages=97–101 |doi=10.1179/cmq.1993.32.2.97|bibcode=1993CaMQ...32...97M}}</ref> Thus, the loss of copper as oxide increases as the copper content of the matte increases.<ref name="Mackey">{{cite journal|author=P J Mackey|title=The Physical Chemistry of Copper Smelting Slags and Copper Losses at the Paipote SmelterPart 2 – Characterisation of industrial slags |year=2011|journal=Canadian Metallurgical Quarterly |volume=50|issue=4|pages=330–340 |bibcode=2011CaMQ...50..330C |s2cid=137350753 |doi=10.1179/000844311X13112418194806}}</ref>

On the other hand, the solubility of sulfidic copper in slag decreases as the copper content of the matte increases beyond about 40%.<ref name="Nagamori"/> Nagamori calculated that more than half the copper dissolved in slags from mattes containing less than 50% copper is sulfidic copper. Above this figure, oxidic copper begins to dominate.<ref name="Nagamori"/>

The loss of copper as prills suspended in the slag depends on the size of the prills, the viscosity of the slag and the settling time available.<ref name="Rosenqvist"/> Rosenqvist suggested that about half the copper losses to slag were due to suspended prills.<ref name="Rosenqvist">T Rosenqvist (2004) ''Principles of Extractive Metallurgy, Second Edition'', Tapir Academic Press: Trondheim, p. 331, {{ISBN|8251919223}}.</ref>

The mass of slag generated in the smelting stage depends on the iron content of the material fed into the smelting furnace and the target matte grade. The greater the iron content of the feed, the more iron that will need to be rejected to the slag for a given matte grade. Similarly, increasing the target matte grade requires the rejection of more iron and an increase in the slag volume.

Thus, the two factors that most affect the loss of copper to slag in the smelting stage are:
* matte grade
* mass of slag.<ref name="Hayes173"/>

This means that there is a practical limit on how high the matte grade can be if the loss of copper to slag is to be minimized. Therefore, further stages of processing (converting and fire refining) are required.

The following subsections briefly describe some of the processes used in matte smelting.

====Reverberatory furnace smelting====

Reverberatory furnaces are long furnaces that can treat wet, dry, or roasted concentrate. Most of the reverberatory furnaces used in the latter years treated roasted concentrate because putting dry feed materials into the reverberatory furnace is more energy efficient, and because the elimination of some of the sulfur in the roaster results in higher matte grades.<ref name="Davenport"/>

The reverberatory furnace feed is added to the furnace through feed holes along the sides of the furnace, and the solid charge is melted.<ref name="Davenport"/> Additional silica is normally added to help form the slag. The furnace is fired with burners using pulverized coal, fuel oil or natural gas<ref name="Gill">C B Gill, ''Non-ferrous Extractive Metallurgy'' (John Wiley & Sons, New York, 1980) pp. 29–35</ref>

Reverberatory furnaces can additionally be fed with molten slag from the later converting stage to recover the contained copper and other materials with a high copper content.<ref name="Gill"/>

Because the reverberatory furnace bath is quiescent, very little oxidation of the feed occurs (and thus very little sulfur is eliminated from the concentrate). It is essentially a melting process.<ref name="Rosenqvist"/> Consequently, wet-charged reverberatory furnaces have less copper in their matte product than calcine-charged furnaces, and they also have lower copper losses to slag.<ref name="Gill"/> Gill quotes a copper in slag value of 0.23% for a wet-charged reverberatory furnace vs 0.37% for a calcine-charged furnace.<ref name="Gill"/>

In the case of calcine-charged furnaces, a significant portion of the sulfur has been eliminated during the roasting stage, and the calcine consists of a mixture of copper and iron oxides and sulfides. The reverberatory furnace acts to allow these species to approach chemical equilibrium at the furnace [[Physics:Operating temperature|operating temperature]] (approximately 1600&nbsp;°C at the burner end of the furnace and about 1200&nbsp;°C at the flue end;<ref>C B Gill, ''Non-ferrous Extractive Metallurgy'' (John Wiley & Sons, New York, 1980) p. 23</ref> the matte is about 1100&nbsp;°C and the slag is about 1195&nbsp;°C<ref name="Gill"/>). In this equilibration process, oxygen associated with copper compounds exchanges with sulfur associated with iron compounds, increasing the iron oxide content of the furnace, and the iron oxides interact with silica and other oxide materials to form the slag.<ref name="Gill"/>

The main equilibration reaction is:

:Cu<sub>2</sub>O + FeS → Cu<sub>2</sub>S + FeO<ref name="Gill"/>

The slag and the matte form distinct layers that can be removed from the furnace as separate streams. The slag layer is periodically allowed to flow through a hole in the wall of the furnace above the height of the matte layer. The matte is removed by draining it through a hole into ladles for it to be carried by crane to the converters.<ref name="Gill"/> This draining process is known as ''tapping'' the furnace.<ref name="Gill"/> The matte taphole is normally a hole through a water-cooled copper block that prevents erosion of the [[Chemistry:Refractory|refractory bricks]] lining the furnace. When the removal of the matte or slag is complete, the hole is normally plugged with clay, which is removed when the furnace is ready to be tapped again.

Reverberatory furnaces were often used to treat molten converter slag to recover contained copper.<ref name="Gill"/> This would be poured into the furnaces from ladles carried by cranes. However, the converter slag is high in magnetite<ref name="Casley">G E Casley, J Middlin and D White, "Recent developments in reverberatory furnace and converter practice at the Mount Isa Mines copper smelter," in: ''Extractive Metallurgy of Copper, Volume 1,'' (The Metallurgical Society: Warrendale, Pennsylvania, 1976), pp. 117–138.</ref> and some of this magnetite would precipitate from the converter slag (due to its higher melting point), forming an accretion on the hearth of the reverberatory furnace and necessitating shut downs of the furnace to remove the accretion.<ref name="Casley"/> This accretion formation limits the quantity of converter slag that can be treated in a reverberatory furnace.<ref name="Casley"/>

While reverberatory furnaces have very low copper losses to slag, they are not very energy-efficient and the low concentrations of sulfur dioxide in their off-gases make its capture uneconomic. Consequently, smelter operators devoted a lot of money in the 1970s and 1980s to developing new, more efficient copper smelting processes.<ref name="Mackey1983">P J Mackey and P Tarassoff, "New and emerging technologies in sulphide [sic] smelting," in: ''Advances in Sulfide Smelting Volume 2: Technology and Practice'', Eds H Y Sohn, D B George and A D Zunkel (The Metallurgical Society of the American Institute of Mining, Metallurgical and Petroleum Engineers: Warrendale, Pennsylvania, 1983), pp. 399–426.</ref> In addition, flash smelting technologies had been developed in earlier years and began to replace reverberatory furnaces. By 2002, 20 of the 30 reverberatory furnaces still operating in 1994 had been shut down.<ref name="Davenport"/>

====Flash furnace smelting====

In [[Chemistry:Flash smelting|flash smelting]], the concentrate is dispersed in an air or oxygen stream and the smelting reactions are largely completed while the mineral particles are still in flight.<ref name="Mackey1983"/> The reacted particles then settle in a bath at the bottom of the furnace, where they behave like calcine in a reverberatory furnace.<ref name="Flash">W G Davenport, M King, M Schlesinger and A K Biswas, ''Extractive Metallurgy of Copper, Fourth Edition'' (Elsevier Science Limited: Kidlington, Oxford, England, 2002), pp. 73–102.</ref> A slag layer forms on top of the matte layer, and they can separately be tapped from the furnace.<ref name="Flash"/>

====ISASMELT====
{{Excerpt|ISASMELT}}

===Converting===
[[File:Tough-Pitch Copper Containing Antimony And Nickel.jpg|thumb|[[Chemistry:Oxygen-free copper|Oxygen-free copper]] aka "Tough-pitch" copper (ca. 98% pure), containing antimony and nickel]]
The matte, which is produced in the smelter, contains 30–70% copper (depending on the process used and the operating philosophy of the smelter), primarily as copper sulfide, as well as iron sulfide. The sulfur is removed at a high temperature as sulfur dioxide by blowing air through molten matte:
:2 CuS + 3 O<sub>2</sub> → 2 CuO + 2 SO<sub>2</sub>

:CuS + O<sub>2</sub> → Cu + SO<sub>2</sub>

In a parallel reaction the iron sulfide is converted to slag:

:2 FeS + 3 O<sub>2</sub> → 2 FeO + 2 SO<sub>2</sub>
:2 FeO + SiO<sub>2</sub> → Fe<sub>2</sub>SiO<sub>4</sub>

The purity of this product is 98%, it is known as ''blister'' because of the broken surface created by the escape of sulfur dioxide gas as blister copper ''pigs'' or ingots are cooled. By-products generated in the process are sulfur dioxide and [[Chemistry:Slag|slag]]. The sulfur dioxide is captured and converted to sulfuric acid and either sold on the open market or used in copper leaching processes.

==Refining==
===Fire refining===
[[File:CopperAnodeRejects.jpg|alt=Copper anodes after fire refining and casting.|thumb|Copper anodes after fire refining and casting.]]
The blister copper is put into an anode furnace, a furnace that refines the blister copper to anode-grade copper in two stages by removing most of the remaining sulfur and iron, and then removing oxygen introduced during the first stage. This second stage, often referred to as ''[[Engineering:Poling (metallurgy)|poling]]'' is done by blowing [[Chemistry:Natural gas|natural gas]], or some other reducing agent, through the molten copper oxide. When this flame burns green, indicating the copper oxidation spectrum, the oxygen has mostly been burned off. This creates copper at about 99% pure.

===Electrolysis===
[[File:CuElectrolyticRefineApparatus.png|thumb|upright=1.35|Apparatus for electrolytic refining of copper]]
{{main|Physics:Electrowinning}}
The final stage in the production of copper is refining. Refining is achieved by [[Chemistry:Electrolysis|electrolysis]], which exploits the easy (low potential) and selective conversion of copper(II) solutions to the metal. The anodes cast from processed blister copper are placed into an [[Chemistry:Aqueous|aqueous]] solution of 3–4% [[Chemistry:Copper(II) sulfate|copper sulfate]] and 10–16% [[Chemistry:Sulfuric acid|sulfuric acid]]. Cathodes are thin rolled sheets of highly pure copper or, more commonly these days, reusable stainless steel starting sheets (as in the [[Engineering:IsaKidd refining technology|IsaKidd process]]).<ref name="Robinson">Robinson T. (2002). "Electrolytic refining."  pp. 265–288 in: ''Extractive Metallurgy of Copper, Fourth Edition''. Eds Davenport W. G., King M., Schlesinger M., and Biswas A. K. (Elsevier Science Limited: Kidlington, Oxford, England).</ref> A potential of only 0.2–0.4 volts is required for the process to commence. In industrial plants current densities up to 420 A/m<sup>2</sup> are possible.<ref>{{Cite report |vauthors=Filzwieser A, Hanel MB, Filzwieser I, Wallner S |date=May 13, 2019 |title=FAQS with regard to operating a Cu ER tankhouse above 400 A/m<sup>2</sup> |url=https://www.mettop.com/api/cdn/uploads/1474547633_4kktjvcg.pdf}}</ref>

At the [[Physics:Anode|anode]] ([[Chemistry:Redox|oxidation]] reaction), copper and less noble metals dissolve. More noble metals and less [[Chemistry:Solubility|soluble]] elements such as [[Chemistry:Silver|silver]], [[Chemistry:Gold|gold]], [[Chemistry:Selenium|selenium]], and [[Chemistry:Tellurium|tellurium]] settle to the bottom of the cell as anode slime, which forms a salable by-product. Copper(II) ions [[Chemistry:Electromigration|migrate]] through the [[Physics:Electrolyte|electrolyte]] to the cathode. At the [[Physics:Cathode|cathode]] ([[Chemistry:Redox|reduction]] reaction), {{chem2|Cu(2+)}} ions are reduced in copper metal and Cu<sub>(s)</sub> plates out, but less noble constituents such as [[Chemistry:Arsenic|arsenic]] and [[Chemistry:Zinc|zinc]] remain in solution unless a higher voltage is used.<ref name="samans">Samans, Carl H. (1949). ''Engineering Metals and their Alloys''. MacMillan.</ref>

The reactions involving metallic copper and {{chem2|Cu(2+)}} ions at the electrodes are the following:
: {|
|-
|– At the [[Physics:Anode|anode]]  || (oxidation and dissolution) || : Cu<sub>(s)</sub>  || → Cu<sup>2+</sup>  + 2 e<sup>−</sup>
|-
|– At the [[Physics:Cathode|cathode]]  || (reduction and precipitation) || : Cu<sup>2+</sup>  +  2 e<sup>−</sup>  || → Cu<sub>(s)</sub>
|}

==Concentrate and copper marketing==

Copper concentrates produced by mines are sold to smelters and refiners who treat the ore and refine the copper and charge for this service via treatment charges (TCs) and refining charges (RCs). The TCs are charged in US$ per tonne of concentrate treated and RCs are charged in cents per pound treated, denominated in US dollars, with benchmark prices set annually by major Japanese smelters. The customer in this case can be a smelter, who on-sells blister copper ingots to a refiner, or a smelter-refiner which is vertically integrated.

One prevalent form of copper concentrate contains gold and silver, like the one produced by Bougainville Copper Limited from the Panguna mine from the early 1970s to the late 1980s.<ref>{{cite web |url=http://www.bcl.com.pg/about-us/about-the-company/ |title=About the Company |access-date=24 August 2015 |archive-url=https://web.archive.org/web/20150923182900/http://www.bcl.com.pg/about-us/about-the-company/ |archive-date=23 September 2015 |url-status=dead }}</ref>

The typical contract for a miner is denominated against the London Metal Exchange price, minus the TC-RCs and any applicable penalties or credits. Penalties may be assessed against copper concentrates according to the level of deleterious elements such as [[Chemistry:Arsenic|arsenic]], [[Chemistry:Bismuth|bismuth]], [[Chemistry:Lead|lead]] or [[Chemistry:Tungsten|tungsten]]. Because a large portion of copper sulfide ore bodies contain [[Chemistry:Silver|silver]] or [[Chemistry:Gold|gold]] in appreciable amounts, a credit can be paid to the miner for these metals if their concentration ''within the concentrate'' is above a certain amount. Usually the refiner or smelter charges the miner a fee based on the concentration; a typical contract will specify that a credit is due for every ounce of the metal in the concentrate above a certain concentration; below that, if it is recovered, the smelter will keep the metal and sell it to defray costs.

Copper concentrate is traded either via [[Finance:Spot contract|spot contract]]s or under long term contracts as an intermediate product in its own right. Often the smelter sells the copper metal itself on behalf of the miner. The miner is paid the price at the time that the smelter-refiner makes the sale, not at the price on the date of delivery of the concentrate. Under a Quotational Pricing system, the price is agreed to be at a fixed date in the future, typically 90 days from time of delivery to the smelter.

A-grade copper cathode is of 99.99% copper in sheets that are 1&nbsp;cm thick, and approximately 1 meter square weighing approximately 200 pounds. It is a true [[Finance:Commodity|commodity]], deliverable to and tradeable upon the metal exchanges in {{wipe|New York City}} (COMEX), [[Place:London|London]] (London Metals Exchange) and [[Place:Shanghai|Shanghai]] (Shanghai Futures Exchange). Often copper cathode is traded upon the exchanges indirectly via warrants, options, or swap contracts such that the majority of copper is traded upon the LME/COMEX/SFE, but delivery is achieved directly, logistically moving the physical copper, and transferring the copper sheet from the physical warehouses themselves.

The chemical specification for [[Physics:Electrolyte|electrolytic]] grade copper is ASTM B 115-00 (a standard that specifies the purity and maximum [[Physics:Electrical resistivity and conductivity|electrical resistivity]] of the product).

==Peak copper==
[[File:Copper - world production trend.svg|thumb|right|300px|World copper production, 1900–2012]]

Peak copper is the point in time at which the maximum global [[Chemistry:Copper|copper]] production rate is reached. Since copper is a finite resource, at some point in the future new production from mining will diminish, and at some earlier time production will reach a maximum. When this will occur is a matter of dispute. Unlike fossil fuels, copper is [[Chemistry:Scrap|scrap]]ped and reused, and it has been estimated that at least 80% of all copper ever mined is still available (having been repeatedly recycled).<ref>{{Cite web|title=Copper Recycling | date=2021|work= Copper Alliance|url=https://copperalliance.org/resource/copper-recycling/|access-date=2023-02-08|language=en-US}}</ref>

Copper is among the most important industrial metals, ranking third after [[Chemistry:Iron|iron]] and [[Chemistry:Aluminium|aluminium]] in terms of quantity used.<ref name="USGS-1">{{Cite web|title=Copper Statistics and Information |website= United States Geological Survey
|author=((National Minerals Information Center))|url=http://minerals.usgs.gov/minerals/pubs/commodity/copper/|access-date=2023-02-08|language=en}}</ref> It is valued for its heat and electrical conductivities, ductility, malleability and resistance to corrosion. Electrical uses account for about three quarters of total copper consumption, including power cables, data cables and electrical equipment. It is also used in cooling and refrigeration tubing, heat exchangers, water pipes and consumer products.<ref name=USGS-1/>

Copper has been used by humans for at least 10,000 years. More than 97% of all copper ever mined and smelted has been extracted since 1900.{{Citation needed|date=March 2022}} The increased demand for copper due to the growing Indian and Chinese economies since 2006 has led to increased prices and an increase in copper theft.<ref name=Leonard2006>{{cite web |url=http://www.salon.com/2006/03/02/peak_copper/ |title=Peak copper? |work=Salon|author=Leonard, Andrew |date=2 March 2006 |access-date=23 March 2008}}</ref>

===History===
Concern about the copper supply is not new.  In 1924 geologist and copper-mining expert Ira Joralemon warned:<ref>{{cite journal|title=Copper and electricity to vanish in twenty years?|journal=Engineering and Mining Journal|date=26 July 1924|volume=118|issue=4|pages=122}}</ref>
:... the age of electricity and of copper will be short.  At the intense rate of production that must come, the copper supply of the world will last hardly a score of years. ... Our civilization based on electrical power will dwindle and die.

===Copper supply===
[[File:2012copper (mined).svg|thumb|300px|right]]
Globally, economic copper resources are being depleted with the equivalent production of three world-class copper mines being consumed annually.<ref name=Leonard2006/> Environmental analyst Lester Brown suggested in 2008 that copper might run out within 25 years based on what he considered a reasonable extrapolation of 2% growth per year.<ref name="Brown">{{cite book |author=Brown, Lester |title=Plan B 2.0: Rescuing a Planet Under Stress and a Civilization in Trouble |publisher=W.W. Norton |year=2006 |location=New York |page=[https://archive.org/details/planb20rescuingp00brow_0/page/109 109] |isbn=0-393-32831-7 |url-access=registration |url=https://archive.org/details/planb20rescuingp00brow_0 }}</ref>

====New copper discoveries====
Fifty-six new copper discoveries have been made during the three decades 1975–2005.<ref name=Leonard2006/> World discoveries of new copper deposits are said to have peaked in 1996.<ref>{{cite web |url=http://news.silverseek.com/CharlestonVoice/1135873932.php |title=Peak Copper Means Peak Silver |work=Charleston Voice |date=29 December 2005 |access-date=9 April 2008 |url-status=dead |archive-url=https://web.archive.org/web/20131104020042/http://news.silverseek.com/CharlestonVoice/1135873932.php |archive-date=4 November 2013 }}</ref> However, according to the US Geological Survey (USGS), remaining world copper reserves have more than doubled since then, from 310 million metric tons in 1996<ref>{{Cite web|last= Edelstein| first= Daniel L.|
title=Copper |series= Mineral Commodity Surveys |publisher= U.S. Geological Survey|url=https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/mineral-pubs/copper/240397.pdf|access-date=2023-02-08|date=February 1997|page=53}}</ref> to 890 million metric tons in 2022.<ref>{{Cite web|last= Flanagan| first= Daniel M.|
title=Copper |series= Mineral Commodity Surveys |publisher= U.S. Geological Survey|url=https://pubs.usgs.gov/periodicals/mcs2023/mcs2023-copper.pdf|access-date=2023-02-08|date=January 2023 | page=2}}</ref>

====Production====
[[File:Top 5 Copper Producers.png|thumb|Production trends in the top five copper-producing nations]]

As shown in the table below, the three chief national producers of copper, respectively, in 2002, were Chile, Indonesia, and the United States. In 2013, they were Chile, China, and Peru. Twenty-one of the 28 largest copper mines in the world (as of 2006) are not amenable to expansion.<ref name=Leonard2006/>

{| class="wikitable sortable" style="text-align:right"
|-
|+ Copper production (thousands tonnes)<ref name=USGS2004>{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/copper/coppemcs04.pdf |title=pg. 54 – Copper |publisher=USGS |year=2004 |access-date=9 April 2008}}</ref><ref name=USGS2006>{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/copper/coppemcs06.pdf |title=pg. 56 – Copper |publisher=USGS |year=2006 |access-date=9 April 2008}}</ref><ref name=USGS2008>{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/copper/mcs-2008-coppe.pdf |title=pg. 54 – Copper |publisher=USGS |year=2008 |access-date=9 April 2008}}</ref><ref name=USGS2010>{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/copper/mcs-2010-coppe.pdf |title=pg. 49 – Copper |publisher=USGS |year=2010 |access-date=15 July 2012}}</ref><ref name=USGS2011>{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/copper/mcs-2011-coppe.pdf |title=pg. 49 – Copper |publisher=USGS |year=2011 |access-date=29 March 2015}}</ref><ref name=USGS2012>{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/copper/mcs-2012-coppe.pdf |title=pg. 49 – Copper |publisher=USGS |year=2012 |access-date=15 July 2012}}</ref><ref name=USGS2013>{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/copper/mcs-2013-coppe.pdf |title=pg. 49 – Copper |publisher=USGS |year=2013 |access-date=29 March 2015}}</ref><ref name=USGS2014>{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/copper/mcs-2014-coppe.pdf |title=pg. 48 – Copper |publisher=USGS |year=2014 |access-date=11 April 2014}}</ref><ref name=USGS2015>{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/copper/mcs-2015-coppe.pdf |title=pg. 49 – Copper |publisher=USGS |year=2015 |access-date=29 March 2015}}</ref><ref name=USGS2016>{{cite web |url=https://minerals.usgs.gov/minerals/pubs/commodity/copper/mcs-2016-coppe.pdf |title=pg. 55 – Copper |publisher=USGS |year=2016 |access-date=29 March 2017}}</ref><ref name=USGS2017>{{cite web |url=https://minerals.usgs.gov/minerals/pubs/commodity/copper/mcs-2017-coppe.pdf |title=pg. 55 – Copper |publisher=USGS |year=2017 |access-date=29 March 2017}}</ref><ref name=USGSds140-coppe2014>{{cite web |url=https://minerals.usgs.gov/minerals/pubs/historical-statistics/ds140-coppe.xlsx |title=Copper Statistics |publisher=USGS |year=2016 |access-date=29 March 2017}}</ref>
|-
! Country
! 2002
! 2003
! 2004
! 2005
! 2006
! 2007
! 2008
! 2009
! 2010
! 2011
! 2012
! 2013
! 2014
! 2015
|-
| style="text-align:left;"| {{flag|Chile}}
| 4,580
| 4,860
| 5,410
| 5,320
| 5,560
| 5,700
| 5,330
| 5,390
| 5,420
| 5,260
| 5,430
| 5,780
| 5,750
| 5,760
|-
| style="text-align:left;"| {{flag|China}}
| 585
| 565
| 620
| 640
| 890
| 920
| 950
| 995
| 1,190
| 1,310
| 1,630
| 1,600
| 1,760
| 1,710
|-
| style="text-align:left;"| {{flag|Peru}}
| 843
| 850
| 1,040
| 1,090
| 1,049
| 1,200
| 1,270
| 1,275
| 1,250
| 1,240
| 1,300
| 1,380
| 1,380
| 1,700
|-
| style="text-align:left;"| {{flag|United States}}
| 1,140
| 1,120
| 1,160
| 1,150
| 1,200
| 1,190
| 1,310
| 1,180
| 1,110
| 1,110
| 1,170
| 1,250
| 1,360
| 1,380
|-
| style="text-align:left;"| {{flag|Australia}}
| 873
| 870
| 854
| 930
| 859
| 860
| 886
| 854
| 870
| 958
| 958
| 990
| 970
| 971
|-
| style="text-align:left;"| {{flag|Congo-Kinshasa}}
| N/A
| N/A
| N/A
| N/A
| N/A
| N/A
| N/A
| N/A
| 343
| 520
| 600
| 970
| 1,030
| 1,020
|-
| style="text-align:left;"| {{flag|Russia}}
| 695
| 700
| 675
| 675
| 725
| 730
| 750
| 725
| 703
| 713
| 883
| 833
| 742
| 732
|-
| style="text-align:left;"| {{flag|Zambia}}
| 330
| 330
| 427
| 450
| 476
| 530
| 546
| 697
| 690
| 668
| 690
| 760
| 708
| 712
|-
| style="text-align:left;"| {{flag|Canada}}
| 600
| 580
| 546
| 580
| 607
| 585
| 607
| 491
| 525
| 566
| 579
| 632
| 696
| 697
|-
| style="text-align:left;"| {{flag|Indonesia}}
| 1,160
| 1,170
| 840
| 1,050
| 816
| 780
| 651
| 996
| 872
| 543
| 360
| 504
| N/A
| N/A
|-
| style="text-align:left;"| {{flag|Mexico}}
| 330
| 330
| 406
| 420
| 338
| 400
| 247
| 238
| 260
| 443
| 440
| 480
| 515
| 594
|-
| style="text-align:left;"| {{flag|Kazakhstan}}
| 490
| 480
| 461
| 400
| 457
| 460
| 420
| 390
| 380
| 417
| 424
| 446
| N/A
| N/A
|-
| style="text-align:left;"| {{flag|Poland}}
| 503
| 500
| 531
| 530
| 512
| 470
| 430
| 439
| 425
| 427
| 427
| 429
| N/A
| N/A
|-
| style="text-align:left;"| ''Other countries''
| 1,500
| 1,500
| 1,610
| 1,750
| 1,835
| 1,800
| 2,030
| 2,190
| 1,900
| 1,970
| 2,000
| 2,200
| 3,600
| 3,800
|- 
! {{noflag}}''World''
! 13,600
! 13,800
! 14,700
! 15,000
! 15,100
! 15,500
! 15,600
! 16,100
! 16,100
! 16,100
! 16,900
! 18,200
! 18,400
! 19,100
|}

====Reserves====
Copper is a [[Earth:Abundance of elements in Earth's crust|fairly common]] element, with an estimated concentration of 50–70&nbsp;ppm (0.005–0.007 percent) in Earth's crust (1&nbsp;kg of copper per 15–20 tons of crustal rock).<ref name=emsley>{{cite book|author=Emsley, John|title=Nature's building blocks: an A–Z guide to the elements|url=https://archive.org/details/naturesbuildingb0000emsl|url-access=registration|year=2003|publisher=Oxford University Press|isbn=978-0-19-850340-8|pages=[https://archive.org/details/naturesbuildingb0000emsl/page/121 121]–125}}</ref> A concentration of 60&nbsp;ppm would multiply out to 1.66 quadrillion [[Tonne|tonne]]s over the {{val|2.77e22|u=kg}} mass of the crust,<ref>{{Cite conference|last1=Peterson|first1=B. T.|last2=Depaolo|first2=D. J.|date=December 2007|title=Mass and Composition of the Continental Crust Estimated Using the CRUST2.0 Model|work=American Geophysical Union Fall Meeting Abstracts |url=https://ui.adsabs.harvard.edu/abs/2007AGUFM.V33A1161P|id=V33A–1161|bibcode=2007AGUFM.V33A1161P }}</ref> or over 90 million years' worth at the 2013 production rate of 18.3&nbsp;MT per year. However, not all of it can be extracted profitably at the current level of technology and the current market value.

The USGS reported a current total reserve base of copper in potentially recoverable ores of 1.6 billion tonnes as of 2005, of which 950 million tonnes were considered economically recoverable.<ref name=Biello2006>{{cite news |url=http://www.sciam.com/article.cfm?id=measure-of-metal-supply-f |title=Measure of Metal Supply Finds Future Shortage |work=Scientific American |author=Biello, David|date=17 January 2006 |access-date=23 March 2008}}</ref> A 2013 global assessment identified "455 known deposits (with well-defined identified resources) that contain about 1.8 billion metric tons of copper", and predicted "a mean of 812 undiscovered deposits within the uppermost kilometer of the earth's surface" containing another 3.1 billion metric tons of copper "which represents about 180 times 2012 global copper production from all types of copper deposits."<ref name=Hammarstrom2013>{{cite news |url=https://gsa.confex.com/gsa/2013AM/webprogram/Paper226200.html |title=Undiscovered Porphyry Copper Resources—A Global Assessment |work=The Geological Society of America: Annual Meeting & Expo |author=Hammarstrom, Jane M. |date=29 October 2013 |access-date=12 April 2014}}</ref>

{| class="wikitable sortable" style="text-align:right"
|-
|+ Copper reserves (thousands of tonnes)<ref name=USGS2015/><ref name=USGS1996>{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/copper/coppemcs96.pdf |title=pg. 50 – Copper |publisher=USGS |year=1996 |access-date=12 April 2014}}</ref>
|-
! Country
! 1996 Reserves
! Percent
! 2015 Reserves
! Percent
|-
| style="text-align:left;"| {{flag|Chile}}
| 88,000
| 28.4%
| 209,000
| 29.9%
|-
| style="text-align:left;"| {{flag|Australia}}
| 7,000
| 2.26%
| 93,000
| 13.2%
|-
| style="text-align:left;"| {{flag|Peru}}
| 7,000
| 2.26%
| 68,000
| 9.71%
|-
| style="text-align:left;"| {{flag|Mexico}}
| N/A
| N/A
| 38,000
| 5.43%
|-
| style="text-align:left;"| {{flag|United States}}
| 45,000
| 14.5%
| 35,000
| 5.00%
|-
| style="text-align:left;"| {{flag|China}}
| 3,000
| 0.968%
| 30,000
| 4.29%
|-
| style="text-align:left;"| {{flag|Russia}}
| 20,000
| 6.45%
| 30,000
| 4.29%
|-
| style="text-align:left;"| {{flag|Poland}}
| 20,000
| 6.45%
| 28,000
| 4.00%
|-
| style="text-align:left;"| {{flag|Indonesia}}
| 11,000
| 3.55%
| 25,000
| 3.57%
|-
| style="text-align:left;"| {{flag|Congo-Kinshasa}}
| N/A
| N/A
| 20,000
| 2.86%
|-
| style="text-align:left;"| {{flag|Zambia}}
| 12,000
| 3.87%
| 20,000
| 2.86%
|-
| style="text-align:left;"| {{flag|Canada}}
| 11,000
| 3.55%
| 11,000
| 1.57%
|-
| style="text-align:left;"| {{flag|Kazakhstan}}
| 14,000
| 4.52%
| 6,000
| 0.86%
|-
| style="text-align:left;"| {{flag|Zaire}}
| 11,000
| 3.55%
| N/A
| N/A
|-
| style="text-align:left;"| {{flag|Philippines}}
| 7,000
| 2.26%
| N/A
| N/A
|-
| style="text-align:left;"| ''Other countries''
| 55,000
| 17.7%
| 90,000
| 12.9%
|-
! style="text-align:left;"| {{noflag}}''World''
! 310,000
! 100%
! 700,000
! 100%
|}

====Known  resources====
=====Recycling=====
In the US, more copper is recovered and put back into service from recycled material than is derived from newly mined ore. Copper's recycle value is so great that premium-grade scrap normally has at least 95% of the value of primary metal from newly mined ore.<ref>{{cite web |url=http://www.copper.org/education/history/g_fact_future.html |title=Copper in the USA: Bright Future – Glorious Past |publisher=Copper Development Association |access-date=9 April 2008 |archive-date=15 August 2013 |archive-url=https://web.archive.org/web/20130815122301/http://www.copper.org/education/history/g_fact_future.html |url-status=dead }}</ref> In Europe, about 50% of copper demand comes from recycling (as of 2016).<ref>{{Cite web |url=https://copperalliance.eu/about-us/europes-copper-industry/ |title=Europe's Copper Industry |access-date=10 January 2019 |archive-date=10 August 2020 |archive-url=https://web.archive.org/web/20200810023232/https://copperalliance.eu/about-us/europes-copper-industry/ |url-status=dead }}</ref>


=====Undiscovered conventional resources=====
Based on discovery rates and existing geologic surveys, researchers estimated in 2006 that 1.6 billion metric tons of copper could be brought into use. This figure relied on the broadest possible definition of available copper as well as a lack of energy constraints and environmental concerns.<ref name=Biello2006/>

The US Geological Survey estimated that, as of 2013, there remained 3.5 billion metric tons of undiscovered copper resources worldwide in porphyry and sediment-hosted type deposits, two types which currently provide 80% of mined copper production.  This was in addition to 2.1 billion metric tons of identified resources. Combined identified and estimated undiscovered copper resources were 5.6 billion metric tons,<ref>Kathleen M. Johnson and others, [http://pubs.usgs.gov/fs/2014/3004/pdf/fs2014-3004.pdf Estimate of undiscovered copper resources of the world, 2013], US Geological Survey, Fact Sheet 2014–3004, Jan. 2014.</ref> 306 times the 2013 global production of newly mined copper of 18.3 million metric tons.

=====Unconventional resources=====
[[Earth:Manganese nodule|Deep-sea nodules]] are estimated to contain 700 million tonnes of copper.<ref name=USGS2008/>

===Criticism===
Julian Simon was a senior fellow at the [[Organization:Cato Institute|Cato Institute]] and a professor of business and economics. In his book ''The Ultimate Resource 2'' (first printed in 1981 and reprinted in 1998), he extensively criticizes the notion of "peak resources", and uses copper as one example. He argues that, even though "peak copper" has been a persistent scare since the early 20th century, "known reserves" grew at a rate that outpaced demand, and the price of copper was not rising but falling over the long run. For example, even though world production of copper in 1950 was only one-eighth of what it was in the early 2000s, known reserves were also much lower at the time – around 100 million metric tons – making it appear that the world would run out of copper in 40 to 50 years at most.

Simon's own explanation for this development is that the very notion of known reserves is deeply flawed,<ref>Simon, Julian (16 February 1998) [http://www.juliansimon.com/writings/Ultimate_Resource/TCHAR12.txt Chapt 12, "People, Materials, and Environment"] in ''The Ultimate Resource II''.</ref> as it does not take into account changes in mining profitability. As richer mines are exhausted, developers turn their attention to poorer sources of the element and eventually develop cheap methods of extracting it, raising known reserves. Thus, for example, copper was so abundant 5000 years ago, occurring in pure form as well as in highly concentrated copper ores, that prehistoric peoples were able to collect and process it with very basic technology. As of the early 21st century, copper is commonly mined from ores that contain 0.3–0.6% copper by weight. Yet, despite the material being far less widespread, the cost of, for example, a copper pot was vastly lower in the late 20th century than 5000 years ago.<ref>{{Cite web|title=The Ultimate Resource II: People, Materials, and Environment|url=http://www.juliansimon.com/writings/Ultimate_Resource/|date=1998|access-date=2023-02-08|last=Simon|first=Julian}}</ref>{{full citation needed|date=July 2023}}

==See also==
{{colbegin}}
* Biomining
* [[:Category:Copper minerals]]
* Copper mining in the United States
* [[Engineering:Extractive metallurgy|Extractive metallurgy]]
* In-situ leach
* List of copper mines
* [[Chemistry:List of countries by copper production|List of countries by copper production]]
* [[Chemistry:Metallurgy|Metallurgy]]
* 2000s commodities boom
* [[Finance:Hubbert peak theory|Hubbert peak theory]]
* [[Chemistry:List of copper alloys|List of copper alloys]]
* [[Earth:Mineral resource classification|Mineral resource classification]]
* [[Chemistry:Peak minerals|Peak minerals]]
{{Div col end}}

==References==
{{Reflist|35em}}

==External links==
* [https://www.copper.org/ Copper.org]
* {{cite web
  |url=http://mazamascience.com/Minerals/USGS
  |title=US Minerals Databrowser
  |publisher=Mazama Science
  |access-date=25 March 2010
  |archive-url=https://web.archive.org/web/20110311113613/http://mazamascience.com/Minerals/USGS/
  |archive-date=11 March 2011
  |url-status=dead
  }}
* {{cite journal|title=Metal Stocks and Sustainability |author=R. B. Gordon*, M. Bertram and T. E. Graedel |journal=Proceedings of the National Academy of Sciences |publisher= U.S. National Academy of Sciences |date=31 January 2006 |pages= 1209–1214 |volume=103 |doi=10.1073/pnas.0509498103 |issue=5 |pmid=16432205 |pmc=1360560|bibcode = 2006PNAS..103.1209G |doi-access=free }}
{{AmCyc Poster|Copper Smelting}}
* The Copper Development Association's [http://www.copper.org/education/production.html copper production] {{Webarchive|url=https://web.archive.org/web/20130907132645/http://www.copper.org/education/production.html |date=2013-09-07 }} page.
* [https://web.archive.org/web/20170505133358/http://www.istc.illinois.edu/info/library_docs/manuals/primmetals/chapter5.htm Copper Processing], from an online text on metals, Illinois Sustainable Technology Center, University of Illinois, archived in May 2017
* [https://web.archive.org/web/20080302034606/http://www.npi.gov.au/database/substance-info/profiles/27.html National Pollutant Inventory – Copper and copper compounds fact sheet]
* University of Pittsburgh School of Engineering Chemical and Petroleum Engineering Department, [http://www.engr.pitt.edu/chemical/undergrad/lab_manuals/flotation.pdf Froth Flotation] {{Webarchive|url=https://web.archive.org/web/20051206091734/http://www.engr.pitt.edu/chemical/undergrad/lab_manuals/flotation.pdf |date=2005-12-06 }} Lab notes.
* [http://chemconnections.org/modules/copper/ Copper Mine], college course syllabus, emphasis on chemistry, last updated 2000

==Bibliography==
* Gill, C. B. (1980) ''Nonferrous Extractive Metallurgy'', John Wiley and Sons: New York, {{ISBN|0471059803}}

{{Extractive metallurgy}}

[[Category:Metallurgical processes]]

{{Sourceattribution|Copper extraction}}