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{{Short description|Manganese dioxide mineral}}
{{Infobox mineral
| name = Pyrolusite
| category = [[Oxide minerals]]
| boxwidth =
| boxbgcolor =
| image = Pyrolusite - USGS ID Stose, GW 1425.jpg
| imagesize =
| caption =
| formula = MnO2
| IMAsymbol = Pyl<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3 |pages=291–320|doi=10.1180/mgm.2021.43 |bibcode=2021MinM...85..291W |s2cid=235729616 |doi-access=free}}</ref>
| molweight =
| strunz = 4.DB.05
| system = [[Tetragonal]]
| class = Ditetragonal dipyramidal (4/mmm) [[H-M symbol]]: (4/m 2/m 2/m)
| symmetry = ''P''42/mnm
| color = Darkish, black to lighter grey, sometimes bluish
| habit = Granular to massive: botryoidal. Crystals rare
| twinning = {031}, {032} may be polysynthetic
| cleavage = Perfect on {110}
| fracture = Irregular/Uneven
| tenacity = Brittle
| mohs = 6–6.5, 2 when massive
| luster = Metallic, dull to earthy
| refractive = Opaque
| opticalprop =
| birefringence =
| pleochroism =
| streak = Black to bluish-black
| gravity = 4.4–5.06
| density =
| melt =
| fusibility =
| diagnostic =
| solubility =
| diaphaneity =
| other =
| references = <ref>[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Pyrolusite Mineralienatlas]</ref><ref name=Webmin>{{Cite web|last1=Barthelmy|first1=David|year=2014|url=http://www.webmineral.com/data/Pyrolusite.shtml|access-date=4 August 2022|title = Pyrolusite Mineral Data|website=Webmineral.com}}</ref><ref name=Mindat>{{mindat|id=3318|title=Pyrolusite|access-date=4 August 2022}}</ref><ref name=Handbook>{{cite web |last1=Anthony |first1=John W. |last2=Bideaux |first2=Richard A. |last3=Bladh |first3=Kenneth W. |last4=Nichols |first4=Monte C. |title=Pyrolusite |url=http://www.handbookofmineralogy.org/pdfs/pyrolusite.pdf |website=Handbook of Mineralogy |publisher=Mineral Data Publishing |access-date=14 March 2022 |date=2005}}</ref>
| var1 = Polianite | var1text = pseudomorphic after [[manganite]]<ref>{{mindat|id=6101|title=Polianite|access-date=4 August 2022}}</ref>
}}

'''Pyrolusite''' is a [[mineral]] consisting essentially of [[manganese dioxide]] ([[manganese|Mn]][[oxygen|O]]2) and is important as an [[ore]] of manganese.<ref name=Ullmann>{{citation | first = Arno H. | last = Reidies | contribution = Manganese Compounds | title = Ullmann's Encyclopedia of Industrial Chemistry | publisher = Wiley-VCH | location = Weinheim | year = 2002 | doi = 10.1002/14356007.a16_123 | volume = 20 | pages = 495–542 | isbn = 978-3-527-30385-4}}.</ref> It is a black, [[amorphous]] appearing mineral, often with a granular, fibrous, or columnar structure, sometimes forming [[wiktionary:reniform#Adjective|reniform]] crusts. It has a metallic [[Lustre (mineralogy)|luster]], a black or bluish-black streak, and readily soils the fingers. The [[specific gravity]] is about 4.8. Its name is from the Greek for ''fire'' and to ''wash'', in reference to its use as a way to remove tints from glass.<ref name=Handbook/>
[[Image:Pyrolusite_radiating.jpg|thumb|Acicular radiating pyrolusite]]

==Occurrence==
[[File:Pyrolusite under normal light.jpg|thumb|upright|A microscopic image of Pyrolusite]]
Pyrolusite and [[romanechite]] are among the most common manganese minerals.
Pyrolusite occurs associated with [[manganite]], [[hollandite]], [[hausmannite]], [[braunite]], [[cryptomelane]], chalcophanite, [[goethite]], and [[hematite]] under [[Redox|oxidizing]] conditions in [[hydrothermal]] deposits. It also occurs in [[bog]]s and often results from alteration of manganite.<ref name=Handbook/>

==Use==
The metal is obtained by reduction of the oxide with [[sodium]], [[magnesium]], [[aluminium]], or by [[electrolysis]]. Pyrolusite is extensively used for the manufacture of [[spiegeleisen]] and [[ferromanganese]] and of various alloys such as manganese-[[bronze]]. As an oxidizing agent it is used in the preparation of [[chlorine]]; indeed, chlorine gas itself was first described by [[Karl Scheele]] in 1774 from the reaction products of pyrolusite and [[hydrochloric acid]]. Natural pyrolusite has been used in batteries, but high-quality batteries require [[manganese dioxide |synthetic products]]. Pyrolusite is also used to prepare disinfectants ([[permanganate]]s) and for decolorizing glass. When mixed with molten glass it oxidizes the ferrous [[iron]] to ferric iron, and so discharges the green and brown tints (making it classically useful to glassmakers as a decolorizer). As a coloring material, it is used in calico printing and dyeing; for imparting violet, [[amber (color)|amber]], and black colors to glass, pottery, and bricks; and in the manufacture of green and violet paints.

==Dendritic manganese oxides==
Black, manganese oxides with a [[Dendrite (crystal)|dendritic]] [[crystal habit]] often found on fracture or rock surfaces are often assumed to be pyrolusite although careful analyses of numerous examples of these dendrites has shown that none of them are, in fact, pyrolusite. Instead, they are other forms of manganese oxide.<ref>Potter, Russell M. and Rossman, George R. (1979) ''Mineralogy of manganese dendrites and coatings.'' American Mineralogist, 64 (11-12). pp. 1219–1226</ref><ref>[http://www.mindat.org/min-26645.html Mn dendrites on Mindat]</ref>

==History==
Some of the most famous early cave paintings in Europe were executed by means of manganese dioxide. Blocks of pyrolusite are found often at [[Neanderthal]] sites. It may have been kept as a pigment for [[cave painting]]s, but it has also been suggested that it was powdered and mixed with [[tinder fungus]] for lighting fires.<ref>{{cite journal |last1=Michael Le Page |title=The original fire starters |journal=New Scientist |date=Jul 28, 2018 |volume=239 |issue=3188 |page=14 |doi=10.1016/S0262-4079(18)31336-8 |bibcode=2018NewSc.239...14L |s2cid=240486296 |url=https://www.newscientist.com/article/mg23931884-200-neanderthal-hand-axes-were-also-used-as-lighters-for-starting-fires/|url-access=subscription }}</ref> Manganese dioxide, in the form of [[umber]], was one of the earliest natural substances used by human ancestors. It was used as a [[pigment]] at least from the [[Middle Paleolithic]]. It may have been also used by the [[Neanderthals]] in fire-making.<ref>{{cite journal | doi=10.1038/srep22159 | title=Selection and Use of Manganese Dioxide by Neanderthals | year=2016 | last1=Heyes | first1=Peter J. | last2=Anastasakis | first2=Konstantinos | last3=De Jong | first3=Wiebren | last4=Van Hoesel | first4=Annelies | last5=Roebroeks | first5=Wil | last6=Soressi | first6=Marie | journal=Scientific Reports | volume=6 | article-number=22159 | pmid=26922901 | pmc=4770591 }}</ref>

The ancient Greeks had a term μάγνης or Μάγνης λίθος ("Magnes lithos") meaning stone of the area called Μαγνησία (Magnesia), referring to [[Magnesia (regional unit)|Magnesia in Thessaly]] or to areas in [[Asia Minor]] with that name. Two minerals are called μάγνης, namely [[lodestone]] and pyrolusite (manganese dioxide).(not to be confused with the current mineral called Lodestone, which does not contain Manganese. Lodestone is a naturally magnetized form of the iron mineral Magnetite. FeFe2O4)
The term μαγνησία was used for manganese dioxide. In the sixteenth century it was called "manganesum". It also was called Alabandicus (from the [[Alabanda]] region of Asia Minor) and Braunstein. Eventually the name of the element manganese was derived from "manganesum", whereas "magnesia" came to mean the oxide of a different element, [[magnesium]].<ref>{{cite web|last=Calvert|first=J. B.|url=http://mysite.du.edu/~jcalvert/phys/chromang.htm|title=Chromium and Manganese|date=2003-01-24|archive-url=https://web.archive.org/web/20161231161307/http://mysite.du.edu/~jcalvert/phys/chromang.htm|archive-date=31 December 2016|df=dmy-all}}</ref>

==See also==
Other manganese oxides:
* [[Birnessite]]
* [[Psilomelane]]

==References==
{{Reflist}}
{{1911|wstitle=Pyrolusite|volume=22|page=693}}

{{Manganese minerals}}
{{ores}}

[[Category:Manganese(IV) minerals]]
[[Category:Oxide minerals]]
[[Category:Rutile group]]
[[Category:Tetragonal minerals]]
[[Category:Minerals in space group 136]]

Pyrolusite - Revision history

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