# Aluminite

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> Markdown URL: https://mediated.wiki/source/Aluminite.md
> Source: https://en.wikipedia.org/wiki/Aluminite
> Source revision: 1302106985
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{{Short description|Sulfate mineral}}
{{For|the [igneous rock](/source/igneous_rock) type "websterite"|Websterite}}
{{infobox mineral
| name        = Aluminite
| category    = [Sulfate mineral](/source/Sulfate_mineral)
| image       = Aluminite - Newhaven, Sussex, England.jpg 
| imagesize   = 260px
| alt         = 
| caption     = Aluminite from Newhaven, Sussex, England
| formula     = Al<sub>2</sub>SO<sub>4</sub>(OH)<sub>4</sub>·7H<sub>2</sub>O
|IMAsymbol=A<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      = 7.DC.05
| dana        = 
| system      = [Monoclinic](/source/Monoclinic)
| class       = Prismatic (2/m) <br/><small>(same [H-M symbol](/source/H-M_symbol))</small>
| symmetry    = ''P''2<sub>1</sub>/c
| unit cell   = a = 7.44, b = 15.583 <br/>c = 11.7&nbsp;[Å]; β = 110.18°; Z&nbsp;=&nbsp;4
| color       = White to grayish white
| colour      = 
| habit       = Needles and fibrous masses
| twinning    = 
| cleavage    = None
| fracture    = Irregular/uneven
| tenacity    = Friable
| mohs        = 1 - 2
| luster      = Dull to earthy
| streak      = White
| diaphaneity = Translucent, opaque if massive
| gravity     = 1.66–1.82
| density     = 
| polish      = 
| opticalprop = Biaxial (+)
| refractive  = n<sub>α</sub> = 1.459 n<sub>β</sub> = 1.464 n<sub>γ</sub> = 1.470
| birefringence = δ = 0.011
| pleochroism = 
| 2V          = Measured: 90°, calculated: 86°
| dispersion  = 
| extinction  = 
| length fast/slow =
| fluorescence = 
| absorption  = 
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = 
| impurities  = 
| alteration  = 
| other       = 
| references  = <ref name=HBM>{{Cite web |url=http://rruff.geo.arizona.edu/doclib/hom/aluminite.pdf |title=Handbook of Mineralogy |access-date=2012-06-10 |archive-date=2012-04-26 |archive-url=https://web.archive.org/web/20120426221857/http://rruff.geo.arizona.edu/doclib/hom/aluminite.pdf |url-status=live }}</ref><ref name=Mindat>{{Cite web |url=http://www.mindat.org/min-154.html |title=Mindat w/ locations |access-date=2005-09-05 |archive-date=2009-11-09 |archive-url=https://web.archive.org/web/20091109185047/http://www.mindat.org/min-154.html |url-status=live }}</ref><ref name=Webmin>{{Cite web |url=http://webmineral.com/data/Aluminite.shtml |title=Webmineral |access-date=2005-09-05 |archive-date=2013-01-17 |archive-url=https://web.archive.org/web/20130117114225/http://webmineral.com/data/Aluminite.shtml |url-status=live }}</ref>
}}

'''Aluminite''' is a hydrous [aluminium](/source/aluminium) [sulfate mineral](/source/sulfate_mineral) with formula: Al<sub>2</sub>SO<sub>4</sub>(OH)<sub>4</sub>·7H<sub>2</sub>O. It is an earthy white to gray-white [monoclinic](/source/monoclinic) mineral which almost never exhibits crystal form. It forms botryoidal to mammillary [clay](/source/clay)-like masses. It has a very soft [Mohs hardness](/source/Mohs_hardness) of 1–2 and a [specific gravity](/source/specific_gravity) of 1.66–1.82. 
[[File:Aluminite outcrop at Newhaven Cliffs.JPG|thumb|left|An outcrop of aluminite at the top of the white chalk of the cliff at [Newhaven, East Sussex](/source/Newhaven%2C_East_Sussex), England.]]

It forms in [clay](/source/clay) and [lignite](/source/lignite) deposits as an [oxidation](/source/oxidation) product of [pyrite](/source/pyrite) and [marcasite](/source/marcasite) along with aluminium silicates. It also occurs in [volcanic sublimate](/source/volcanic_sublimate)s, in [native sulfur](/source/native_sulfur) deposits and rarely in [cave](/source/cave)s. It occurs in association with [basaluminite](/source/basaluminite), [gibbsite](/source/gibbsite), [epsomite](/source/epsomite), [gypsum](/source/gypsum), [celestine](/source/Celestine_(mineral)), [dolomite](/source/Dolomite_(mineral)) and [goethite](/source/goethite).<ref name=HBM/>

It was first described in 1807 from [Halle](/source/Halle%2C_Saxony-Anhalt), [Saxony-Anhalt](/source/Saxony-Anhalt), [Germany](/source/Germany) and named for its aluminium content.<ref name=Mindat/> It is also known as ''alley stone'', ''halite'' and ''websterite'' (named after [Orcadian](/source/Orcadians) geologist [Thomas Webster](/source/Thomas_Webster_(geologist))).

Aluminite is used by tile and masonry workers to reduce the setting time of mortars.{{cn|date=June 2012}}

==References==
{{Reflist}}

==External links==
*{{Commons category-inline}}

Category:Aluminium minerals
Category:Sulfate minerals
Category:Monoclinic minerals
Category:Minerals in space group 14
Category:Luminescent minerals
[https://www.youtube.com/watch?v=SuSQKdGFG_M Drone Video of the Outcrop at Newhaven]

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Adapted from the Wikipedia article [Aluminite](https://en.wikipedia.org/wiki/Aluminite) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Aluminite?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.