View source for Autunite

{{Short description|Type of phosphate mineral}}
{{Infobox mineral
| name        = Autunite
| boxwidth    = 
| boxbgcolor  =#d2d75e 
| image       = Autunite-69257.jpg
| imagesize   = 
| alt         = 
| caption     = Autunite from Daybreak Mine, Washington
| category    = [[Phosphate minerals]]
| formula     = Ca(UO<sub>2</sub>)<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>·10–12H<sub>2</sub>O
|IMAsymbol=Aut<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   = 986.26 g/mol
| strunz      = 8.EB.05
| dana        = 
| system      = [[Orthorhombic crystal system|Orthorhombic]]
| class       = Dipyramidal (mmm) <br/>[[H-M symbol]]: (2/m 2/m 2/m)
| symmetry    = ''Pnma'' 
| unit cell   = a = 14.0135(6), <br/>b = 20.7121(8), <br/>c = 6.9959(3)&nbsp;[Å]; Z&nbsp;=&nbsp;4
| color       = Lemon-yellow to sulfur-yellow, greenish yellow to pale green; may be dark green to greenish black 
| colour      = 
| habit       = Tabular crystals, foliated or scaly aggregates, and in crusts
| twinning    = Rare on {110}
| cleavage    = {001} perfect, {100} and {010} poor 
| fracture    = uneven
| tenacity    = 
| mohs        = 2–2.5 
| luster      = Vitreous – pearly
| streak      = Pale yellow
| diaphaneity = Transparent to translucent
| gravity     = 3.1–3.2
| density     = 3.15 
| polish      = 
| opticalprop = Biaxial (−)
| refractive  = n<sub>α</sub> = 1.553 – 1.555 n<sub>β</sub> = 1.575 n<sub>γ</sub> = 1.577 – 1.578 
| birefringence = δ = 0.003
| pleochroism = X = colorless to pale yellow; Y = Z = yellow to dark yellow
| 2V          = Measured: 10° to 53°
| dispersion  = 
| extinction  = 
| length fast/slow =
| fluorescence = Strong yellow-green fluorescence in UV; Radioactive
| absorption  = 
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = Soluble in acids
| impurities  = 
| alteration  = Dehydrates in air
| other       = Pseudotetragonal for synthetic material, [[Image:Radioactive.svg|25px]] [[Radioactive]]
| references  = <ref name=Mindat>[http://www.mindat.org/min-433.html Mindat.org]</ref><ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/autunite.pdf Handbook of Mineralogy]</ref>
}}

'''Autunite''' (hydrated calcium uranyl phosphate), with formula Ca(UO<sub>2</sub>)<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>·10–12H<sub>2</sub>O, is a yellow-greenish [[fluorescence|fluorescent]] [[Phosphate minerals|phosphate]] [[mineral]] with a [[Mohs scale of mineral hardness|hardness]] of 2–{{frac|2|1|2}}.<ref>{{Cite web|url=http://webmineral.com/data/Autunite.shtml|title=Autunite Mineral Data|last=Barthelmy|first=Dave|website=webmineral.com|access-date=2018-01-26}}</ref><ref name=":0">{{Cite web|url=https://www.mindat.org/min-433.html|title=Autunite: Autunite mineral information and data.|website=www.mindat.org|access-date=2018-04-28}}</ref> Autunite crystallizes in the [[Orthorhombic crystal system|orthorhombic]] system and often occurs as tabular square [[crystal]]s, commonly in small crusts or in fan-like masses. Due to the moderate [[uranium]] content of 48.27% it is [[Radioactive decay|radioactive]] and also used as uranium ore. Autunite fluoresces bright green to lime green under UV light. The mineral is also called '''calco-uranite''', but this name is rarely used and effectively outdated.<ref name=":1">{{cite EB1911|wstitle=Autunite |volume= 03 |short= x}}</ref>

Autunite was discovered in 1852 near [[Autun]], [[France]], which is also autunite's namesake. It occurs as an [[redox|oxidation]] product of uranium minerals in [[granite]] [[pegmatite]]s and [[hydrothermal circulation|hydrothermal]] deposits. Associate minerals include [[metaautunite]], [[torbernite]], [[phosphuranylite]], [[saleeite]], [[uranophane]] and [[sabugalite]].<ref name=HBM/>

== Etymology ==
Autunite was named after the town of Autun, France, where the mineral was initially found. The mineral was named by Henry J. Brooke and William H. Miller in 1854.<ref name=":0" /> The archaic name "calco-uranite" pairs with the similarly composed mineral, [[torbernite]], which was named "cupro-uranite". Both minerals are named due to their uranium content, with autunite's name referring to its calcium (''calco''), and torbernite's copper (''cupro'') quantity.<ref name=":1" />

== Locations and mining ==

=== Mount Kit Carson, Washington ===
[[File:Autunite-rl-aut8a.jpg|left|thumb|224x224px|Autunite from Mount Kit Carson, Washington]]
Researchers found autunite inside the Daybreak Mine on [[Mount Kit Carson]], [[Spokane]], [[Washington (state)|Washington]] (or sometimes referred to as "near [[Mount Spokane]]"), in "[[Vug|vugs]], [[Fracture (geology)|fractures]], and [[Shear (geology)|shear zones]] in [[Granite|granitic rock]]". These areas showed signs of another phosphate, [[apatite]], which may have helped lead to the formation of autunite, by providing a source of [[phosphate]] and [[Lime (material)|lime]]. The formation may have occurred with the interaction of uranium leached from a separate deposit.<ref>{{Cite book|title=Autunite from Mt. Spokane, Washington|last=G. W. Leo|publisher=The American Mineralogist|year=1960|location=U.S. Geologic Survey, Menlo Park, California|pages=1}}</ref>

90,000&nbsp;lbs of [[Triuranium octoxide|U<sub>3</sub>O<sub>8</sub>]] were produced from nine properties, although most of the ore came from the Daybreak Mine.<ref>[http://pubs.usgs.gov/of/1998/of98-503/of98-503.pdf USGS]</ref>

=== Other locations ===
One of the other locations of autunite includes Autun, France, the type locality and namesake of the mineral. The mineral was formed there as an [[Mineral alteration|alteration]] of [[uraninite]] and other [[uranium]] bearing minerals.<ref>{{Cite book|url=https://books.google.com/books?id=BmcirNqupXcC&pg=PA149|title=Nature Guide: Rocks and Minerals|last=Publishing|first=D. K.|date=2012-06-18|publisher=Penguin|isbn=9781465403520|language=en}}</ref> Autunite is also found in [[Cornwall]], [[Saxony]], and [[North Dakota|North]] and [[South Dakota]].<ref>{{Cite book|url=https://archive.org/details/encyclopediaame04unkngoog|page=[https://archive.org/details/encyclopediaame04unkngoog/page/n803 669]|title=The Encyclopedia Americana: A Library of Universal Knowledge|date=1918|publisher=Encyclopedia Americana Corporation|language=en}}</ref><ref name=":1" />

== Meta-autunite ==
If the mineral dries out, it can lose its water content and convert to meta-autunite-I, which can turn into meta-autunite-II after heating. These two subsequent minerals are very rare in nature. For scientific studies it is recommended to store the mineral in a sealed container to minimize the water loss. Museums are known to have covered the mineral with [[lacquer]] to avoid drying of the mineral.

== Gallery ==
<gallery>
File:Autunite UV(AB) France.jpg|Autunite under UV light
File:Autunite sous UV (France).jpg|More crystals under UV light
File:Autunite09.jpg|Scaly crystals of autunite
File:Autunite (France).JPG|Autunite from France
File:Autunite-141164.jpg|Close-up of an autunite crystal
</gallery>

== References ==
<references />{{commons category|Autunite}}
{{Wikisource1911Enc|Autunite}}
[[Category:Calcium minerals]]
[[Category:Uranium(VI) minerals]]
[[Category:Phosphate minerals]]
[[Category:Orthorhombic minerals]]
[[Category:Minerals in space group 62]]
[[Category:Luminescent minerals]]
[[Category:Radioactive minerals]]
[[Category:Minerals described in 1854]]