Editing Manganese (section)

==Occurrence==
{{See also|Category:Manganese minerals}}
Manganese comprises about 1000&nbsp;[[Parts per million|ppm]] (0.1%) of the [[Earth's crust]] and is the [[Abundance of elements in Earth's crust|12th most abundant element]].<ref name="Emsley2001">{{cite book|title=Nature's Building Blocks: An A-Z Guide to the Elements|last=Emsley|first=John|publisher=Oxford University Press|date=2001|location=Oxford, UK|isbn=978-0-19-850340-8|chapter=Manganese|pages=[https://archive.org/details/naturesbuildingb0000emsl/page/249 249–253]|chapter-url=https://books.google.com/books?id=j-Xu07p3cKwC|url=https://archive.org/details/naturesbuildingb0000emsl/page/249}}</ref> Soil contains 7–9000&nbsp;ppm of manganese with an average of 440&nbsp;ppm.<ref name="Emsley2001" /> The atmosphere contains 0.01&nbsp;μg/m<sup>3</sup>.<ref name="Emsley2001" /> Manganese occurs principally as [[pyrolusite]] ([[manganese(IV) oxide|MnO<sub>2</sub>]]), [[braunite]] (Mn<sup>2+</sup>Mn<sup>3+</sup><sub>6</sub>)SiO<sub>12</sub>),<ref>{{cite journal|pages=65–71 |journal=Contributions to Mineralogy and Petrology|title=Geochemistry of braunite and associated phases in metamorphosed non-calcareous manganese ores of India|first=P. K.|last=Bhattacharyya|author2=Dasgupta, Somnath |author3=Fukuoka, M. |author4=Roy Supriya |doi=10.1007/BF00371403|date=1984|volume=87|issue=1|bibcode=1984CoMP...87...65B|s2cid=129495326}}</ref> [[psilomelane]] {{chem2|(Ba,H2O)2Mn5O10}}, and to a lesser extent as [[rhodochrosite]] ([[manganese(II) carbonate|MnCO<sub>3</sub>]]).

{|class="wikitable"
|[[File:ManganeseOreUSGOV.jpg|center|120px]]
|[[File:Mineraly.sk - psilomelan.jpg|center|140px]]
|[[File:Spiegeleisen.jpg|center|150px]]
|[[File:Dendrites01.jpg|center|130px]]
|[[File:The Searchlight Rhodochrosite Crystal.jpg|center|140px]]
|-
|Manganese ore
|Psilomelane (manganese ore)
|[[Spiegeleisen]] is an iron alloy with a manganese content of approximately 15%.
|Manganese oxide dendrites on limestone from [[Solnhofen]], Germany – a kind of [[pseudofossil]]. Scale is in mm
|Mineral [[rhodochrosite]] ([[manganese(II) carbonate]])
|}
[[File:World Manganese Production 2006.svg|thumb|upright=1.6|Percentage of manganese output in 2006 by countries<ref name="USGSMCS2009">{{Cite report|url=https://pubs.usgs.gov/publication/mineral2009 |title=Mineral Commodity Summaries 2009 |date=2009 |publisher=Water Resources Division, U.S. Geological Survey |doi=10.3133/mineral2009}}</ref>]]

The most important manganese ore is pyrolusite ([[manganese(IV) oxide|MnO<sub>2</sub>]]). Other economically important manganese ores usually show a close spatial relation to the iron ores, such as [[sphalerite]].<ref name="Holl" /><ref>{{Cite journal|last1=Cook|first1=Nigel J.|last2=Ciobanu|first2=Cristiana L.|last3=Pring|first3=Allan|last4=Skinner|first4=William|last5=Shimizu|first5=Masaaki|last6=Danyushevsky|first6=Leonid|last7=Saini-Eidukat|first7=Bernhardt|last8=Melcher|first8=Frank|date=2009|title=Trace and minor elements in sphalerite: A LA-ICPMS study|url=https://linkinghub.elsevier.com/retrieve/pii/S0016703709003263|journal=Geochimica et Cosmochimica Acta|language=en|volume=73|issue=16|pages=4761–4791|doi=10.1016/j.gca.2009.05.045|bibcode=2009GeCoA..73.4761C}}</ref> Land-based resources are large but irregularly distributed. About 80% of the known world manganese resources are in South Africa; other important manganese deposits are in Ukraine, Australia, India, China, [[Gabon]] and Brazil.<ref name="USGSMCS2009"/>

Manganese is mainly mined in South Africa, Australia, China, Gabon, Brazil, India, Kazakhstan, Ghana, Ukraine and Malaysia.<ref>{{Cite journal|doi = 10.1007/s11837-018-2769-4|title = Review of Manganese Processing for Production of TRIP/TWIP Steels, Part 1: Current Practice and Processing Fundamentals|journal = JOM |volume = 70|issue = 5|pages = 680–690|year = 2018|last1 = Elliott|first1 = R|last2 = Coley|first2 = K|last3 = Mostaghel|first3 = S|last4 = Barati|first4 = M|bibcode = 2018JOM....70e.680E|s2cid = 139950857}}</ref> In South Africa, most identified deposits are located near [[Hotazel]] in the [[Northern Cape Province]], ([[Kalahari manganese fields]]), with a 2011 estimate of 15&nbsp;billion tons. In 2011 South Africa produced 3.4&nbsp;million tons, topping all other nations.<ref name="Mbendi">{{cite web |url=http://www.mbendi.com/indy/ming/mang/af/sa/p0005.htm |title=Manganese Mining in South Africa – Overview |publisher=MBendi Information Services |access-date=10 December 2022 |url-status=dead |archive-url=https://web.archive.org/web/20160205194737/http://www.mbendi.com/indy/ming/mang/af/sa/p0005.htm |archive-date=5 February 2016}}</ref>

===Oceanic environment===
{{Main|Manganese nodule}}
An abundant resource of manganese in the form of manganese nodules found on the ocean floor.<ref>{{cite book |last1=Hein |first1=James R. |title=Encyclopedia of Marine Geosciences - Manganese Nodules |date=January 2016 |publisher=Springer |pages=408–412 |url=https://www.researchgate.net/publication/306107551 |access-date=2 February 2021}}</ref> These nodules, which are composed of 29% manganese,<ref>{{cite web |last1=International Seabed Authority |title=Polymetallic Nodules |url=https://isa.org.jm/files/files/documents/eng7.pdf |website=isa.org |publisher=International Seabed Authority |access-date=2 February 2021 |archive-date=23 October 2021 |archive-url=https://web.archive.org/web/20211023145629/https://isa.org.jm/files/files/documents/eng7.pdf |url-status=dead }}</ref> are located along the [[seabed|ocean floor]]. The [[Environmental issues|environmental impacts]] of nodule collection are of interest.<ref>{{Cite journal|last1=Oebius|first1=Horst U|last2=Becker|first2=Hermann J|last3=Rolinski|first3=Susanne|last4=Jankowski|first4=Jacek A|date=January 2001|title=Parametrization and evaluation of marine environmental impacts produced by deep-sea manganese nodule mining|url=http://dx.doi.org/10.1016/s0967-0645(01)00052-2|journal=Deep Sea Research Part II: Topical Studies in Oceanography|volume=48|issue=17–18|pages=3453–3467|doi=10.1016/s0967-0645(01)00052-2|bibcode=2001DSRII..48.3453O|issn=0967-0645}}</ref><ref>{{cite journal |last1=Thompson |first1=Kirsten F. |last2=Miller |first2=Kathryn A. |last3=Currie |first3=Duncan |last4=Johnston |first4=Paul |last5=Santillo |first5=David |title=Seabed Mining and Approaches to Governance of the Deep Seabed |journal=Frontiers in Marine Science |date=2018 |volume=5 |page=480 |doi=10.3389/fmars.2018.00480 |s2cid=54465407 |doi-access=free |bibcode=2018FrMaS...5..480T |hdl=10871/130176 |hdl-access=free }}</ref> According to 1978 estimate, the [[ocean floor]] has 500&nbsp;billion tons of [[manganese nodule]]s.<ref>{{cite journal|doi=10.1016/j.micron.2008.10.005|pages=350–358|date=2009|title=Manganese/polymetallic nodules: micro-structural characterization of exolithobiontic- and endolithobiontic microbial biofilms by scanning electron microscopy|volume=40 |issue=3|pmid=19027306|journal=Micron |author1=Wang, X|author2=Schröder, HC|author3=Wiens, M|author4=Schlossmacher, U|author5=Müller, WEG}}</ref> {{As of|2025|April}}, attempts to find economically viable methods of harvesting manganese nodules are still ongoing, however, none has been commercialized.<ref>{{Cite web |title=Exploration Contracts |url=https://www.isa.org.jm/exploration-contracts/ |access-date=4 April 2025 |publisher=International Seabed Authority|date=17 March 2022 }}</ref>

In 1972, the [[Central Intelligence Agency|CIA]]'s [[Project Azorian]], through billionaire [[Howard Hughes]], commissioned the ship ''[[Hughes Glomar Explorer]]'' with the cover story of harvesting [[manganese nodules]] from the sea floor.<ref>{{Cite news|url=https://www.bbc.com/news/science-environment-42994812|title=The CIA secret on the ocean floor|date=19 February 2018|work=BBC News|access-date=3 May 2018|language=en-GB}}</ref> This cover story triggered a rush of activity to collect manganese nodules. The real mission of ''Hughes Glomar Explorer'' was to raise a sunken [[Union of Soviet Socialist Republics|Soviet]] submarine, the [[Soviet submarine K-129 (1960)|K-129]], with the goal of retrieving Soviet code books.<ref name="azorian">{{cite web |url=http://www2.gwu.edu/~nsarchiv/nukevault/ebb305/index.htm |title=Project Azorian: The CIA's Declassified History of the Glomar Explorer |publisher=National Security Archive at George Washington University |date=12 February 2010 |access-date=18 September 2013}}</ref>

Manganese also occurs in the oceanic environment, as dissolved manganese (dMn), which is found throughout the world's oceans, 90% of which originates from hydrothermal vents.<ref name="Hernroth-2020">{{Cite journal|last1=Hernroth|first1=Bodil|last2=Tassidis|first2=Helena|last3=Baden|first3=Susanne P.|date=March 2020|title=Immunosuppression of aquatic organisms exposed to elevated levels of manganese: From global to molecular perspective|url=http://dx.doi.org/10.1016/j.dci.2019.103536|journal=Developmental & Comparative Immunology|volume=104|pages=103536|doi=10.1016/j.dci.2019.103536|pmid=31705914|s2cid=207935992|issn=0145-305X}}</ref> Particulate Mn develops in buoyant plumes over an active vent source, while the dMn behaves conservatively.<ref name="Ray-2017">{{Cite journal|last1=Ray|first1=Durbar|last2=Babu|first2=E. V. S. S. K.|last3=Surya Prakash|first3=L.|date=1 January 2017|title=Nature of Suspended Particles in Hydrothermal Plume at 3°40'N Carlsberg Ridge:A Comparison with Deep Oceanic Suspended Matter|journal=Current Science|volume=112|issue=1|pages=139|doi=10.18520/cs/v112/i01/139-146 |issn=0011-3891|doi-access=free}}</ref> Mn concentrations vary between the water columns of the ocean. At the surface, dMn is elevated due to input from external sources such as rivers, dust, and shelf sediments. Coastal sediments normally have lower Mn concentrations, but can increase due to anthropogenic discharges from industries such as mining and steel manufacturing, which enter the ocean from river inputs. Surface dMn concentrations can also be elevated biologically through photosynthesis and physically from coastal upwelling and wind-driven surface currents. Internal cycling such as photo-reduction from UV radiation can also elevate levels by speeding up the dissolution of Mn-oxides and oxidative scavenging, preventing Mn from sinking to deeper waters.<ref name="Sim-2019">{{Cite journal|last1=Sim|first1=Nari|last2=Orians|first2=Kristin J.|date=October 2019|title=Annual variability of dissolved manganese in Northeast Pacific along Line-P: 2010–2013|url=http://dx.doi.org/10.1016/j.marchem.2019.103702|journal=Marine Chemistry|volume=216|pages=103702|doi=10.1016/j.marchem.2019.103702|bibcode=2019MarCh.21603702S |s2cid=203151735|issn=0304-4203}}</ref> Elevated levels at mid-depths can occur near mid-ocean ridges and hydrothermal vents. The hydrothermal vents release dMn enriched fluid into the water. The dMn can then travel up to 4,000&nbsp;km due to the microbial capsules present, preventing exchange with particles, lowing the sinking rates. Dissolved Mn concentrations are even higher when oxygen levels are low. Overall, dMn concentrations are normally higher in coastal regions and decrease when moving offshore.<ref name="Sim-2019"/>

=== Soils ===
Manganese occurs in soils in three oxidation states: the divalent cation, Mn<sup>2+</sup> and as brownish-black oxides and hydroxides containing Mn (III,IV), such as MnOOH and MnO<sub>2</sub>. Soil pH and oxidation-reduction conditions affect which of these three forms of Mn is dominant in a given soil. At pH values less than 6 or under anaerobic conditions, Mn(II) dominates, while under more alkaline and aerobic conditions, Mn(III,IV) oxides and hydroxides predominate. These effects of soil acidity and aeration state on the form of Mn can be modified or controlled by microbial activity. Microbial respiration can cause both the oxidation of Mn<sup>2+</sup> to the oxides, and it can cause reduction of the oxides to the divalent cation.<ref>{{Cite book|last1=Bartlett|first1=Richmond|title=Chemical Processes in Soils|last2=Ross|first2=Donald|publisher=Soil Science Society of America|year=2005|editor-last=Tabatabai|editor-first=M.A.|series=SSSA Book Series, no. 8|location=Madison, Wisconsin|pages=461–487|chapter=Chemistry of Redox Processes in Soils|lccn=2005924447|editor-last2=Sparks|editor-first2=D.L.}}</ref>

The Mn(III,IV) oxides exist as brownish-black stains and small nodules on sand, silt, and clay particles. These surface coatings on other soil particles have high surface area and carry negative charge. The charged sites can adsorb and retain various cations, especially heavy metals (e.g., Cr<sup>3+</sup>, Cu<sup>2+</sup>, Zn<sup>2+</sup>, and Pb<sup>2+</sup>). In addition, the oxides can adsorb organic acids and other compounds. The adsorption of the metals and organic compounds can then cause them to be oxidized while the Mn(III,IV) oxides are reduced to Mn<sup>2+</sup> (e.g., Cr<sup>3+</sup> to Cr(VI) and colorless [[hydroquinone]] to tea-colored [[quinone]] polymers).<ref>{{Cite book|last1=Dixon|first1=Joe B.|title=Soil Mineralogy with Environmental Applications|last2=White|first2=G. Norman|publisher=Soil Science Society of America|year=2002|editor-last=Dixon|editor-first=J.B.|series=SSSA Book Series no. 7|location=Madison, Wisconsin|pages=367–386|chapter=Manganese Oxides|lccn=2002100258|editor-last2=Schulze|editor-first2=D.G.}}</ref>