Editing Silver (section)

==Occurrence and production==
{{further|Silver mining}}
[[File:Silver - world production trend.svg|thumb|World production of silver]]
The abundance of silver in the Earth's crust is 0.08&nbsp;[[parts per million]], almost exactly the same as that of [[mercury (element)|mercury]]. It mostly occurs in [[sulfide]] ores, especially [[acanthite]] and [[argentite]], Ag<sub>2</sub>S. Argentite deposits sometimes also contain [[native metal|native]] silver when they occur in reducing environments, and when in contact with salt water they are converted to [[chlorargyrite]] (including [[horn silver]]), AgCl, which is prevalent in [[Chile]] and [[New South Wales]].<ref name="Greenwood and Earnshaw-3">Greenwood and Earnshaw, pp. 1174–67</ref> Most other silver minerals are silver [[pnictide]]s or [[chalcogenide]]s; they are generally lustrous semiconductors. Most true silver deposits, as opposed to argentiferous deposits of other metals, came from [[Tertiary period]] vulcanism.<ref name="Brumby et al-3">Brumby et al., pp. 21–22</ref>

The principal sources of silver are the ores of copper, copper-nickel, lead, and lead-zinc obtained from [[Peru]], [[Bolivia]], [[Mexico]], [[China]], [[Australia]], [[Chile]], [[Poland]] and [[Serbia]].<ref name="Hammond-2004" /> Peru, Bolivia and Mexico have been mining silver since 1546, and are still major world producers. Top silver-producing mines are [[Cannington Mine|Cannington]] (Australia), [[Mina Proaño|Fresnillo]] (Mexico), [[San Cristóbal mine (Bolivia)|San Cristóbal]] (Bolivia), [[Antamina mine|Antamina]] (Peru), [[Rudna mine|Rudna]] (Poland), and [[Peñasquito Polymetallic Mine|Penasquito]] (Mexico).<ref name="CPM Group-2011">{{cite book|author=CPM Group|title=CPM Silver Yearbook|date=2011|publisher=Euromoney Books|location=New York |isbn=978-0-9826741-4-7|page=68}}</ref> Top near-term mine development projects through 2015 are Pascua Lama (Chile), Navidad (Argentina), Jaunicipio (Mexico), Malku Khota (Bolivia),<ref>{{cite web|title=Preliminary Economic Assessment Technical Report 43-101|url=http://www.soamsilver.com/upload/Technical_Reports/Malku_Khota_PEA_Update_11_May_2011.pdf.pdf|archive-url=https://web.archive.org/web/20120119090432/http://www.soamsilver.com/upload/Technical_Reports/Malku_Khota_PEA_Update_11_May_2011.pdf.pdf|archive-date=19 January 2012|publisher=South American Silver Corp.}}</ref> and Hackett River (Canada).<ref name="CPM Group-2011" /> In [[Central Asia]], [[Mining in Tajikistan#Silver|Tajikistan]] is known to have some of the largest silver deposits in the world.<ref>{{cite news|url=http://www.eurasianet.org/node/67365 |title=Why Are Kyrgyzstan and Tajikistan So Split on Foreign Mining? |newspaper=Eurasianet |publisher=EurasiaNet.org |date=7 August 2013 |access-date=19 August 2013}}</ref>

Silver is usually found in nature combined with other metals, or in minerals that contain silver compounds, generally in the form of [[sulfides]] such as [[galena]] (lead sulfide) or [[cerussite]] (lead carbonate). So the primary production of silver requires the smelting and then [[cupellation]] of argentiferous lead ores, a historically important process.<ref name="Kassianidou-2003">Kassianidou, V. (2003). "Early Extraction of Silver from Complex Polymetallic Ores", pp. 198–206 in Craddock, P.T. and Lang, J (eds.) ''Mining and Metal production through the Ages''. London, British Museum Press.</ref> Lead melts at 327&nbsp;°C, lead oxide at 888&nbsp;°C and silver melts at 960&nbsp;°C. To separate the silver, the alloy is melted again at the high temperature of 960&nbsp;°C to 1000&nbsp;°C in an oxidising environment. The lead oxidises to [[Lead(II) oxide|lead monoxide]], then known as [[litharge]], which captures the oxygen from the other metals present. The liquid lead oxide is removed or absorbed by [[capillary action]] into the hearth linings.<ref>Craddock, P.T. (1995). ''Early metal mining and production''. Edinburgh: Edinburgh University Press. p. 223. {{ISBN|1560985356}}</ref><ref name="Bayley-2008">
Bayley, J., Crossley, D. and Ponting, M. (eds). (2008). [https://www.researchgate.net/publication/271133104_Metals_and_Metalworking_A_Research_Framework_for_Archaeometallurgy ''Metals and Metalworking. A research framework for archaeometallurgy''. Historical Metallurgy Society. p. 6. {{ISBN|978-0-9560225-0-9}}</ref><ref>Pernicka, E., Rehren, Th., Schmitt-Strecker, S. (1998). [https://www.academia.edu/7001043/Late_Uruk_silver_production_by_cupellation_at_Habuba_Kabira_Syria_Pernicka_et_al_1998_ "Late Uruk silver production by cupellation at Habuba Kabira, Syria"], pp. 123–34 in ''Metallurgica Antiqua'', Deutsches Bergbau-Museum.</ref>
: {{Chem|Ag}}(s) + 2{{Chem|Pb}}(s) + {{Chem|O|2}}(g) → 2{{Chem|Pb|O}}(absorbed) + Ag(l)

Today, silver metal is primarily produced instead as a secondary byproduct of [[Refining (metallurgy)#Electrolytic refining|electrolytic refining]] of copper, lead, and zinc, and by application of the [[Parkes process]] on lead bullion from ore that also contains silver.<ref name="Hilliard" /> In such processes, silver follows the non-ferrous metal in question through its concentration and smelting, and is later purified out. For example, in copper production, purified copper is [[electrolysis|electrolytically]] deposited on the cathode, while the less reactive precious metals such as silver and gold collect under the anode as the so-called "anode slime". This is then separated and purified of base metals by treatment with hot aerated dilute [[sulfuric]] acid and heating with lime or silica flux, before the silver is purified to over 99.9% purity via electrolysis in [[nitrate]] solution.<ref name="Greenwood and Earnshaw-3" />

Commercial-grade fine silver is at least 99.9% pure, and purities greater than 99.999% are available. In 2022, Mexico was the top producer of silver (6,300 [[tonne]]s or 24.2% of the world's total of 26,000 t), followed by China (3,600 t) and Peru (3,100 t).<ref name="Hilliard">{{cite web|url=http://minerals.usgs.gov/minerals/pubs/commodity/silver/|title=Silver|author=Hilliard, Henry E.|publisher=USGS|access-date=4 June 2006|archive-date=6 January 2019|archive-url=https://web.archive.org/web/20190106233737/http://minerals.usgs.gov/minerals/pubs/commodity/silver/|url-status=dead}}</ref>

===In marine environments===
Silver concentration is low in [[seawater]] (pmol/L). Levels vary by depth and between water bodies. Dissolved silver concentrations range from 0.3&nbsp;pmol/L in coastal surface waters to 22.8&nbsp;pmol/L in pelagic deep waters.<ref name="Barriada-2007">{{cite journal|last1=Barriada|first1=Jose L.|last2=Tappin|first2=Alan D.|last3=Evans|first3=E. Hywel|last4=Achterberg|first4=Eric P.|title=Dissolved silver measurements in seawater|journal=TrAC Trends in Analytical Chemistry|volume=26|issue=8|year=2007|pages=809–817|doi=10.1016/j.trac.2007.06.004}}</ref> Analysing the presence and dynamics of silver in marine environments is difficult due to these particularly low concentrations and complex interactions in the environment.<ref name="Fischer-2018">{{cite journal|last1=Fischer|first1=Lisa|last2=Smith|first2=Geoffrey|last3=Hann|first3=Stephan|last4=Bruland|first4=Kenneth W.|title=Ultra-trace analysis of silver and platinum in seawater by ICP-SFMS after off-line matrix separation and pre-concentration|journal=Marine Chemistry|volume=199|year=2018|pages=44–52|doi=10.1016/j.marchem.2018.01.006|bibcode=2018MarCh.199...44F |doi-access=free}}</ref> Although a rare trace metal, concentrations are greatly impacted by fluvial, aeolian, atmospheric, and upwelling inputs, as well as anthropogenic inputs via discharge, waste disposal, and emissions from industrial companies.<ref name="Ndung’u-2001">{{cite journal|last1=Ndung’u|first1=K.|last2=Thomas|first2=M.A.|last3=Flegal|first3=A.R.|title=Silver in the western equatorial and South Atlantic Ocean|journal=Deep Sea Research Part II: Topical Studies in Oceanography|volume=48|issue=13|year=2001|pages=2933–2945|doi=10.1016/S0967-0645(01)00025-X|bibcode=2001DSRII..48.2933N}}</ref><ref name="Zhang-2001">{{cite journal|last1=Zhang|first1=Yan|last2=Amakawa|first2=Hiroshi|last3=Nozaki|first3=Yoshiyuki|title=Oceanic profiles of dissolved silver: precise measurements in the basins of western North Pacific, Sea of Okhotsk, and the Japan Sea|journal=Marine Chemistry|volume=75|issue=1–2|year=2001|pages=151–163|doi=10.1016/S0304-4203(01)00035-4|bibcode=2001MarCh..75..151Z }}</ref> Other internal processes such as decomposition of organic matter may be a source of dissolved silver in deeper waters, which feeds into some surface waters through upwelling and vertical mixing.<ref name="Zhang-2001" />

In the Atlantic and Pacific, silver concentrations are minimal at the surface but rise in deeper waters.<ref name="Flegal-1995">{{cite journal|last1=Flegal|first1=A.R.|last2=Sañudo-Wilhelmy|first2=S.A.|last3=Scelfo|first3=G.M.|title=Silver in the Eastern Atlantic Ocean|journal=Marine Chemistry|volume=49|issue=4|year=1995|pages=315–320|doi=10.1016/0304-4203(95)00021-I|bibcode=1995MarCh..49..315F }}</ref> Silver is taken up by plankton in the photic zone, remobilized with depth, and enriched in deep waters. Silver is transported from the Atlantic to the other oceanic water masses.<ref name="Ndung’u-2001" /> In North Pacific waters, silver is remobilised at a slower rate and increasingly enriched compared to deep Atlantic waters. Silver has increasing concentrations that follow the major oceanic conveyor belt that cycles water and nutrients from the North Atlantic to the South Atlantic to the North Pacific.<ref name="Ranville-2005">{{cite journal|last1=Ranville|first1=Mara A.|last2=Flegal|first2=A. Russell|title=Silver in the North Pacific Ocean|journal=Geochemistry, Geophysics, Geosystems|volume=6|issue=3|year=2005|pages=n/a|doi=10.1029/2004GC000770|bibcode=2005GGG.....6.3M01R|doi-access=free}}</ref>

There is not an extensive amount of data focused on how marine life is affected by silver despite the likely deleterious effects it could have on organisms through [[bioaccumulation]], association with particulate matters, and [[sorption]].<ref name="Barriada-2007" /> Not until about 1984 did scientists begin to understand the chemical characteristics of silver and the potential toxicity. In fact, [[Mercury (element)|mercury]] is the only other trace metal that surpasses the toxic effects of silver; the full silver toxicity extent is not expected in oceanic conditions because of its tendency to transfer into nonreactive biological compounds.<ref name="Ratte-1999">{{cite journal|last1=Ratte|first1=Hans Toni|title=Bioaccumulation and toxicity of silver compounds: A review|journal=Environmental Toxicology and Chemistry|volume=18|issue=1|year=1999|pages=89–108|doi=10.1002/etc.5620180112|s2cid=129765758 |doi-access=free|bibcode=1999EnvTC..18...89R }}</ref>

In one study, the presence of excess ionic silver and silver [[nanoparticle]]s caused bioaccumulation effects on zebrafish organs and altered the chemical pathways within their gills.<ref name="Lacave-2018">{{cite journal|last1=Lacave|first1=José María|last2=Vicario-Parés|first2=Unai|last3=Bilbao|first3=Eider|last4=Gilliland|first4=Douglas|last5=Mura|first5=Francesco|last6=Dini|first6=Luciana|last7=Cajaraville|first7=Miren P.|last8=Orbea|first8=Amaia|title=Waterborne exposure of adult zebrafish to silver nanoparticles and to ionic silver results in differential silver accumulation and effects at cellular and molecular levels|journal=Science of the Total Environment|volume=642|year=2018|pages=1209–1220|doi=10.1016/j.scitotenv.2018.06.128|pmid=30045502|bibcode=2018ScTEn.642.1209L|s2cid=51719111}}</ref> In addition, very early experimental studies demonstrated how the toxic effects of silver fluctuate with salinity and other parameters, as well as between life stages and different species such as finfish, molluscs, and crustaceans.<ref>{{cite journal|author1=Calabrese, A.|author2= Thurberg, F.P.|author3= Gould, E. |year=1977|title=Effects of Cadmium, Mercury, and Silver on Marine Animals|journal= Marine Fisheries Review|volume= 39|issue=4|pages=5–11|url=
https://fliphtml5.com/hzci/lbsc/basic |archive-url=https://web.archive.org/web/20210126043259/https://fliphtml5.com/hzci/lbsc/basic |archive-date=26 January 2021 }}</ref> Another study found raised concentrations of silver in the muscles and liver of dolphins and whales, indicating pollution of this metal within recent decades. Silver is not an easy metal for an organism to eliminate and elevated concentrations can cause death.<ref name="Chen-2017">{{cite journal|last1=Chen|first1=Meng-Hsien|last2=Zhuang|first2=Ming-Feng|last3=Chou|first3=Lien-Siang|last4=Liu|first4=Jean-Yi|last5=Shih|first5=Chieh-Chih|last6=Chen|first6=Chiee-Young|title=Tissue concentrations of four Taiwanese toothed cetaceans indicating the silver and cadmium pollution in the western Pacific Ocean|journal=Marine Pollution Bulletin|volume=124|issue=2|year=2017|pages=993–1000|doi=10.1016/j.marpolbul.2017.03.028|pmid=28442199|bibcode=2017MarPB.124..993C }}</ref>