View source for Goethite

{{Short description|Iron(III) oxide-hydroxide named in honor to the poet Goethe}}
{{Infobox mineral
| name        = Goethite
| category    = [[oxide minerals]] hydroxide subgroup
| image       = Goethite-169735.jpg 
| caption     = 
| formula     = α-[[Iron|Fe]][[Oxygen|O]]([[Hydroxide|OH]])
| IMAsymbol   = Gth<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.FD.10
| system      = [[Orthorhombic]]
| class       = Dipyramidal (mmm) <br/>[[H–M symbol]]: (2/m 2/m 2/m)
| symmetry    = ''Pbnm''
| color       = Yellowish to reddish to dark brown or black
| habit       = Radial acicular, mammillary, botryoidal, stalactitic, massive, as encrustation, as pseudomorph; may be banded or iridescent 
| twinning    = 
| cleavage    = Perfect {010}
| fracture    = Uneven to splintery
| mohs        = 5.0–5.5
| luster      = Adamantine to dull
| refractive  = Opaque to sub-translucent
| opticalprop = 
| birefringence = 
| pleochroism = 
| streak      = Brown, brownish yellow to orange yellow
| gravity     = 3.3–4.3
| density     = 
| melt        = 
| fusibility  = Fusible at 5–5.5
| diagnostic  = 
| solubility  = HCl soluble
| diaphaneity = 
| other       = weakly magnetic
| references  = <ref name=HurlbutKlein1985>{{cite book |last1=Hurlbut |first1=Cornelius S. |last2=Klein |first2=Cornelis |year=1985 |title=Manual of Mineralogy |edition=20th |publisher=Wiley |isbn=0-471-80580-7 |url-access=registration |url=https://archive.org/details/manualofmineralo00klei }}</ref><ref name=Barthelmy2012>{{cite web |last1=Barthelmy |first1=David |title=Goethite Mineral Data |url=http://webmineral.com/data/Goethite.shtml |website=Mineralogy Database |access-date=8 April 2022 |date=2012}}</ref><ref name=Mindat>{{mindat|title=Goethite|id=1719}}</ref><ref name=HOM>{{cite web |last1=Anthony |first1=John W. |last2=Bideaux |first2=Richard A. |last3=Bladh |first3=Kenneth W. |last4=Nichols |first4=Monte C. |title=Goethite |url=http://www.handbookofmineralogy.org/pdfs/goethite.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.handbookofmineralogy.org/pdfs/goethite.pdf |archive-date=2022-10-09 |url-status=live |website=Handbook of Mineralogy |publisher=Mineral Data Publishing |access-date=14 March 2022 |date=2005}}</ref>
}}
[[File:Goethite-182557.jpg|thumb|upright|Unusual specimen of goethite replacing a [[gypsum]] [[stalactite]]; the center is hollow. From [[Santa Eulalia, Chihuahua]], Mexico.]]
'''Goethite''' ({{IPAc-en|ˈ|ɡ|ɜːr|t|aɪ|t}},<ref>{{Cite dictionary |url=http://www.lexico.com/definition/goethite |archive-url=https://web.archive.org/web/20210805045033/https://www.lexico.com/definition/goethite |url-status=dead |archive-date=August 5, 2021 |title=goethite |dictionary=[[Lexico]] UK English Dictionary |publisher=[[Oxford University Press]]}}</ref><ref>{{cite Merriam-Webster|goethite}}</ref> {{IPAc-en|usalso|ˈ|ɡ|oʊ|θ|aɪ|t}}<ref>{{cite Dictionary.com|goethite}}</ref><ref>{{cite American Heritage Dictionary|goethite}}</ref>) is a mineral of the [[diaspore]] group, consisting of [[iron(III) oxide-hydroxide]], specifically the α-[[Polymorphism (materials science)|polymorph]]. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient times for its use as a [[pigment]] (brown [[ochre]]). Evidence has been found of its use in paint pigment samples taken from the [[Lascaux|caves of Lascaux]] in [[France]]. It was first described in 1806 based on samples found in the Hollertszug Mine in [[Herdorf]], [[Germany]].<ref name=Mindat/> The mineral was named after the [[Germany|German]] [[polymath]] and poet [[Johann Wolfgang von Goethe]] (1749–1832).

== Composition ==
Goethite is an [[Iron(III) oxide-hydroxide|iron oxyhydroxide]] containing [[ferric]] iron. It is the main component of [[rust]] and [[bog iron]] ore. Goethite's hardness ranges from 5.0 to 5.5 on the [[Mohs scale of mineral hardness|Mohs Scale]], and its [[specific gravity]] varies from 3.3 to 4.3. The mineral forms prismatic needle-like [[crystal]]s ("needle ironstone"<ref name=Barthelmy2012/>) but is more typically massive.<ref name=HurlbutKlein1985/>

[[Feroxyhyte]] and [[lepidocrocite]] are both [[Polymorphism (materials science)|polymorph]]s of the iron oxyhydroxide FeO(OH) which are stable at the pressure and temperature conditions of the Earth's surface. Although they have the same chemical formula as goethite, their different crystalline structures make them distinct minerals.<ref name=HOM/>

Additionally, goethite has several high-pressure and high-temperature [[Polymorphism (materials science)|polymorph]]s, which may be relevant to the conditions of the Earth's interior. These include ε-FeOOH, which has an orthorhombic crystal structure,<ref>{{cite journal |doi=10.1007/s00269-009-0319-x |title=High-pressure X-ray diffraction study of ε-FeOOH |journal=Physics and Chemistry of Minerals |volume=37 |issue=3 |pages=153–157 |year=2010 |last1=Suzuki |first1=Akio |bibcode=2010PCM....37..153S |s2cid=92941002 }}</ref> a cubic [[pyrite]]-type polymorph with<ref>{{cite journal |doi=10.1038/nature18018 |title=FeO<sub>2</sub> and FeOOH under deep lower-mantle conditions and Earth's oxygen–hydrogen cycles |journal=Nature |volume=534 |issue=7606 |pages=241–244 |year=2016 |last1=Hu |first1=Qingyang |last2=Kim |first2=Duckyoung |last3=Yang |first3=Wenge |last4=Liuxiang |first4=Yang |last5=Yue |first5=Meng |last6=Zhang |first6=Li |last7=Mao |first7=Ho-kwang|pmid=27279220 |bibcode=2016Natur.534..241H |s2cid=10702618 }}</ref> or without losing hydrogen<ref>{{cite journal |doi=10.1038/nature22823 |title=The pyrite-type high-pressure form of ε-FeOOH |journal=Nature |volume=547 |issue=7662 |pages=205–208 |year=2017 |last1=Nishi |first1=Masayuki |last2=Kuwayama |first2=Yasuhiro |last3=Tsuchiya |first3=Jun |last4=Tsuchiya |first4=Taku |pmid=28678774 |bibcode=2017Natur.547..205N |s2cid=205257075 }}</ref> and an ultradense hexagonal structure.<ref>{{cite journal |doi=10.1073/pnas.1720510115 |pmid=29507221 |title=Discovery of a hexagonal ultradense hydrous phase in (Fe,Al)OOH |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=547 |issue=12 |pages=205–208 |year=2017 |last1=Zhang |first1=Li |last2=Yuan |first2=Hongsheng |last3=Meng |first3=Yue |last4=Mao |first4=Ho-kwang |pmc=5866593 |doi-access=free }}</ref>

Goethite has the same crystal structure as [[diaspore]], the analogous aluminium oxide-hydroxide mineral. Oxygen and hydroxide ions form a hexagonal close-packed structure, with iron ions filling octahedral sites between the anions. The sites filled by iron ions form paired chains running the length of the crystal, with the two chains in each pair joined by hydroxide ions.{{sfn|Hurlbut|Klein|1985|p=392}}

<gallery>
File:Goethite c.png|The goethite crystal structure viewed along [001]. Red ions are iron, white are oxygen, and yellow are hydroxide.
File:Goethite b.png|The goethite crystal structure viewed along [010]
</gallery>

== Formation ==
[[File:Geothite.jpg|thumb|A microscopic picture of goethite (name misspelled on picture)]]
Goethite often forms through the [[weathering]] of other iron-rich minerals, and thus is a common component of [[soil]]s, concentrated in [[laterite]] soils. [[Nanoparticle|Nanoparticulate]] [[authigenic]] goethite is a common [[Diagenesis|diagenetic]] iron oxyhydroxide in both marine and lake sediments.<ref>{{cite journal |doi=10.1130/G19924.1 |title=Nanogoethite is the dominant reactive oxyhydroxide phase in lake and marine sediments |journal=Geology |volume=31 |issue=11 |pages=993 |year=2003 |last1=Van Der Zee |first1=Claar |last2=Roberts |first2=Darryl R. |last3=Rancourt |first3=Denis G. |last4=Slomp |first4=Caroline P. |author-link=Caroline Slomp|bibcode=2003Geo....31..993V |hdl=1874/31393 |s2cid=130357956 |hdl-access=free }}</ref> The formation of goethite is marked by the oxidation state change of Fe<sup>2+</sup> (ferrous) to Fe<sup>3+</sup> (ferric), which allows for goethite to exist at surface conditions. Because of this oxidation state change, goethite is commonly seen as a [[pseudomorph]]. As iron-bearing minerals are brought to the zone of oxidation within the soil, the iron turns from iron(II) to iron(III), while the original shape of the parent mineral is retained. Common goethite pseudomorphs include [[pyrite]], [[siderite]], and [[marcasite]], though any iron(II)-bearing mineral could become a goethite pseudomorph if proper conditions are met. It may also be precipitated by [[groundwater]] or in other sedimentary conditions, or form as a primary mineral in [[hydrothermal]] deposits. Goethite has also been found to be produced by the excretion processes of certain bacteria types.<ref>{{cite journal |doi=10.1016/j.gca.2010.03.037 |title=Biomineralization of lepidocrocite and goethite by nitrate-reducing Fe(II)-oxidizing bacteria: Effect of pH, bicarbonate, phosphate, and humic acids |journal=Geochimica et Cosmochimica Acta |volume=74 |issue=13 |pages=3721–34 |year=2010 |last1=Larese-Casanova |first1=Philip |last2=Haderlein |first2=Stefan B. |last3=Kappler |first3=Andreas |bibcode=2010GeCoA..74.3721L }}</ref>

== Distribution ==
Goethite is found all over the planet, usually in the form of [[concretion]]s, [[stalactite|stalactitic]] formations, [[oolite]]s (a form consisting of tiny round grains cemented together),<ref name=Mindat/> reniform (kidney shapes) or botryoidal (globular, like bunches of grapes) accumulations. It is also a very common pseudomorph. It is frequently encountered in the swampy areas at the head of spring waters ('[[bog iron]]'), on cave floors, and on the bottom of lakes and small creeks. The ''boxworks'' or [[gossan]] resulting from the [[oxidation]] of sulfide ore deposits is formed of goethite along with other iron oxides and quartz.<ref name=Sinkankas1964>{{cite book |last1=Sinkankas |first1=John |title=Mineralogy for amateurs. |date=1964 |publisher=Van Nostrand |location=Princeton, N.J. |isbn=0442276249 |pages=342–344}}</ref><ref name=HurlbutKlein1985/>

Significant deposits of goethite are found in [[England]]; [[Cuba]]; and [[Minnesota]], [[Missouri]], [[Colorado]], [[Alabama]], [[Georgia (U.S. state)|Georgia]], [[Virginia]], and [[Tennessee]], in the [[United States]].<ref name=Sinkankas1964/><ref name=HurlbutKlein1985/>

Deposits significant in location, if not in abundance, have been found in the [[Mars|Martian]] crater [[Gusev (Martian crater)|Gusev]] by NASA's ''[[MER-A|Spirit]]'' rover, providing strong evidence for the presence of liquid water on the planet in an earlier stage of its evolution.<ref>{{cite journal |last1=Klingelhöfer |first1=G. |last2=DeGrave |first2=E. |last3=Morris |first3=R. V. |last4=Van Alboom |first4=A. |last5=de Resende |first5=V. G. |last6=De Souza |first6=P. A. |last7=Rodionov |first7=D. |last8=Schröder |first8=C. |last9=Ming |first9=D. W. |last10=Yen |first10=A. |title=Mössbauer spectroscopy on Mars: goethite in the Columbia Hills at Gusev crater |journal=Hyperfine Interactions |date=November 2005 |volume=166 |issue=1–4 |pages=549–554 |doi=10.1007/s10751-006-9329-y|bibcode=2005HyInt.166..549K |s2cid=95186141 |url=https://biblio.ugent.be/publication/538524/file/538971 |url-access=subscription }}</ref>

[[Limpet]]s' teeth are composed of about 80% goethite fibres of only tens of nanometers in diameter, small enough to be [[monocrystalline whisker|flaw-insensitive]], which accounts for their extreme [[tensile strength]] of 3.5–6.0&nbsp;GPa and [[elastic modulus]] of {{val|120|30|u=GPa}}.<ref name="BBCLimpet">{{cite web | url=https://www.bbc.co.uk/news/science-environment-31500883 | title=Limpet teeth set new strength record | publisher=[[BBC]] News | work=BBC News: Science and Environment | date=18 February 2015 | access-date=23 December 2016 | author=Webb, Jonathan}}</ref><ref>{{Cite journal
|title=Extreme strength observed in limpet teeth
|first1=Asa H.|last1=Barber
|first2=Dun|last2=Lu
|first3=Nicola M.|last3=Pugno
|date=2015-04-06
|doi=10.1098/rsif.2014.1326
|publisher=[[Royal Society]]
|journal=J. R. Soc. Interface |volume=12 <!-- not shown‽ -->
|issue=105
|at=20141326
|doi-access=free
|pmid = 25694539
|pmc = 4387522
}}</ref>

== Usage ==
Its main modern use is as an [[iron ore]], being referred to as ''brown iron ore''.<ref name=Mindat/> Goethite is an important component of [[ochre]] pigments,<ref>{{cite journal |last1=Hradil |first1=David |last2=Grygar |first2=Tomáš |last3=Hradilová |first3=Janka |last4=Bezdička |first4=Petr |title=Clay and iron oxide pigments in the history of painting |journal=Applied Clay Science |date=April 2003 |volume=22 |issue=5 |pages=223–236 |doi=10.1016/S0169-1317(03)00076-0|bibcode=2003ApCS...22..223H }}</ref> and has been heat-treated for use as a red pigment since [[Paleolithic]] times.<ref>{{cite journal |last1=Cavallo |first1=G. |last2=Fontana |first2=F. |last3=Gialanella |first3=S. |last4=Gonzato |first4=F. |last5=Riccardi |first5=M. P. |last6=Zorzin |first6=R. |last7=Peresani |first7=M. |title=Heat Treatment of Mineral Pigment During the Upper Palaeolithic in North-East Italy: Heat treatment of mineral pigment during the Upper Palaeolithic |journal=Archaeometry |date=October 2018 |volume=60 |issue=5 |pages=1045–1061 |doi=10.1111/arcm.12360}}</ref> Iron-rich [[laterite|lateritic]] soils that have developed over [[serpentinite]] rocks in tropical climates are mined for their iron content, as well as other metals.<ref>{{cite journal |last1=Frasche |first1=Dean F. |title=Origin of the Surigao iron ores |journal=Economic Geology |date=1 May 1941 |volume=36 |issue=3 |pages=280–305 |doi=10.2113/gsecongeo.36.3.280|bibcode=1941EcGeo..36..280F }}</ref>

Fine goethite specimens are rare and therefore are valued collectibles.<ref name=Sinkankas1964/> Banded or iridescent varieties are cut and polished into [[cabochons]] for jewelry making.<ref>{{cite journal |last1=Gosse |first1=Ralph |title=Notes on Rare and Unusual New England Gemstones |journal=Rocks & Minerals |date=October 1968 |volume=43 |issue=10 |pages=753–756 |doi=10.1080/00357529.1968.11765131|bibcode=1968RoMin..43..753G }}</ref>

In a royal tomb of the ancient kingdom of [[Phrygia]], a body was found believed to be King [[Gordias]], father of the legendary King [[Midas]]. The burial shroud had been colored with a dye containing goethite, which in its original un-faded state would have made the shroud look as though it were woven from gold. Historians speculate that the legend of King Midas' golden touch might have originated from Phrygian royalty wearing clothes made from such golden-colored textiles.<ref>{{cite book |last1=Ballard |first1=Mary |title=The archaeology of Phrygian Gordion, royal city of Midas |date=2012 |publisher=University of Pennsylvania Museum of Archaeology and Anthropology |location=Philadelphia |isbn=9781934536483 |pages=15, 165–169 |url=https://books.google.com/books?id=TUkiGrcsN28C&q=goethite |access-date=8 April 2022 |chapter=King Midas' Textiles and His Golden Touch |editor-first1=C. Brian |editor-last1=Rose}}</ref><ref>Archived at [https://ghostarchive.org/varchive/youtube/20211211/NPgZhBagmbk Ghostarchive]{{cbignore}} and the [https://web.archive.org/web/20160830231151/https://www.youtube.com/watch?v=NPgZhBagmbk&gl=US&hl=en Wayback Machine]{{cbignore}}: {{cite web|last1=Rose|first1=Brian|title=Great Myths and Legends: The Golden Age of King Midas|url=https://www.youtube.com/watch?v=NPgZhBagmbk|publisher=Penn Museum|access-date=27 August 2016}}{{cbignore}}</ref>

==Gallery==
<gallery widths="120" heights="120">
File:Goethite-242608.jpg|[[Iridescent]] goethite, Filón Sur Mine, [[Tharsis, Huelva]], Spain
File:Goethite3.jpg|Goethite from [[Minas Gerais]], Brazil
File:Goethite-Calcite-Feldspar-Group-215498.jpg|A sharp, disc-shaped calcite has here been completely replaced by goethite, which preserved the original form perfectly
File:PyOx.JPG|Goethite coating/replacing rusted [[pyrite]] cubes
File:Goethite-162473.jpg|Finely crystallized specimen of goethite from [[Lake George, Colorado|Lake George]], Park County, [[Colorado]], US
File:Harvard Museum of Natural History. Goethite. Negaunee, Marquette Co., MI (DerHexer) 2012-07-20.jpg|Goethite from Negaunee, Marquette County, Michigan
</gallery>

==See also==
*[[Limpet#Teeth|Limpet teeth]]
*[[Ochre]]
*[[List of minerals]]
*[[List of minerals named after people]]

==References==
{{Reflist}}

==External links==
{{Commons category|Goethite}}
* {{Cite EB1911 |last=Spencer |first=Leonard James |author-link=Leonard James Spencer |wstitle=Göthite |short=x}}

{{Authority control}}

[[Category:Iron(III) minerals]]
[[Category:Iron oxide pigments]]
[[Category:Hydroxide minerals]]
[[Category:Johann Wolfgang von Goethe]]
[[Category:Orthorhombic minerals]]
[[Category:Minerals in space group 62]]
[[Category:Iron ores]]
[[Category:Magnetic minerals]]
[[Category:Minerals described in 1806]]