Editing Albite

{{short description|Tectosilicate mineral, plagioclase feldspar variety}}
{{Infobox mineral
| name        = Albite
| category    = [[Tectosilicate]] [[minerals]], [[feldspar]] [[Mineral group|group]], [[plagioclase]] series
| boxwidth    = 
| boxbgcolor  =#afada3 
| image       = Albite - Crete (Kriti) Island, Greece.jpg
| imagesize   = 
| caption     = {{ubl|Albite from Crete|(scale = {{convert|1|in|abbr=on}})}}
| formula     = {{chem|NaAlSi|3|O|8}} or {{chem|Na|1.0–0.9|Ca|0.0–0.1|Al|1.0–1.1|Si|3.0–2.9|O|8}}
|IMAsymbol=Ab<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      = 9.FA.35
| system      = [[Triclinic]]
| class       = {{ubl|Pinacoidal ({{overline|1}})|(same [[H-M symbol]])}}
| symmetry    = ''C''{{overline|1}}
| unit cell   = {{ubl|1=a = 8.16, b = 12.87|2=c = 7.11&nbsp;[Å]; α = 93.45°|3=β = 116.4°, γ = 90.28°; Z&nbsp;=&nbsp;4}}
| color       = White to gray, blueish, greenish, reddish; may be [[chatoyant]]
| habit       = Crystals commonly tabular, divergent aggregates, granular, cleavable massive
| twinning    = Common giving polysynthetic striae on {001} or {010} also contact, simple and multiple
| cleavage    = Perfect on {001}, very good on {010}, imperfect on {110}
| fracture    = Uneven to conchoidal
| tenacity    = Brittle
| mohs        = 6–6.5
| luster      = Vitreous, typically pearly on cleavages
| polish      = 
| refractive  = {{ubl|1=''n''<sub>α</sub> = 1.528–1.533|2=''n''<sub>β</sub> = 1.532–1.537|3=''n''<sub>γ</sub> = 1.538–1.542}}
| opticalprop = Biaxial (+)
| birefringence = ''δ'' = 0.010
| dispersion  = ''r'' < ''v'' weak
| pleochroism = 
| 2V          = 85–90° (low); 52–54° (high)
| melt        = {{convert|1100|-|1120|°C|abbr=on}}
| fluorescence= 
| absorption  =
| streak      = White
| gravity     = 2.60–2.65
| density     = 
| fusibility  = 
| diagnostic  = 
| solubility  = 
| diaphaneity = Transparent to translucent
| other       = Low- and high-temperature structural modifications are recognized
| references  = <ref name=Handbook>[http://rruff.geo.arizona.edu/doclib/hom/albite.pdf Handbook of Mineralogy]</ref><ref name= Mindat>[http://www.mindat.org/min-96.html Mindat.org]</ref><ref name=Webmin>[http://www.webmineral.com/data/Albite.shtml Webmineral data]</ref>
}}

'''Albite''' is a [[plagioclase]] [[feldspar]] [[mineral]]. It is the sodium [[Endmember (mineralogy)|endmember]] of the plagioclase [[solid solution]] series. It represents a plagioclase with less than 10% [[anorthite]] content. The pure albite endmember has the formula {{chem|[[sodium|Na]][[aluminium|Al]][[silicon|Si]]|3|[[oxygen|O]]|8}}. It is a [[Silicate minerals|tectosilicate]]. Its color is usually pure white, hence its name from [[Latin]], {{lang|la|albus}}.<ref>{{EB1911|wstitle=Albite|inline=1}}</ref> It is a common constituent in [[felsic]] rocks.



== Properties ==
Albite crystallizes with [[triclinic]] pinacoidal forms. Its [[specific gravity]] is about 2.62 and it has a [[Mohs hardness]] of 6 to 6.5. Albite almost always exhibits [[crystal twinning]] often as minute parallel striations on the crystal face. Albite often occurs as fine parallel segregations alternating with pink [[microcline]] in [[perthite]] as a result of exolution on cooling.

There are two variants of albite, which are referred to as 'low albite' and 'high albite'; the latter is also known as 'analbite'. Although both variants are triclinic, they differ in the volume of their unit cell, which is slightly larger for the 'high' form. The 'high' form can be produced from the 'low' form by heating above {{convert|750|°C|°F|abbr=on}}<ref>{{cite journal|first=O. F. |last1=Tuttle |first2=N. L. |last2=Bowen |date=1950 |title=High-temperature albite and contiguous feldspars |journal=Journal of Geology |volume=58 |issue=5 |pages=572–583 |url=https://www.jstor.org/stable/30068571}}</ref> High albite can be found in meteor impact craters such as in [[Winslow, Arizona]].<ref>{{Cite web|url=https://www.mindat.org/loc-3317.html|title=High Albite|website=www.mindat.org}}</ref> Upon further heating to more than {{convert|1050|°C|abbr=on}} the [[crystal symmetry]] changes from triclinic to [[monoclinic]]; this variant is also known as 'monalbite'.<ref>[http://www.mindat.org/min-34160.html Monalbite on Mindat]</ref> Albite melts at {{convert|1100|-|1120|°C|abbr=on}}.<ref>{{cite journal|doi=10.1029/98JB02300 |first1=J. P. |last1=Greenwood |first2=P. C. |last2=Hess |date=1998 |title=Congruent melting of albite: theory and experiment |journal=Journal of Geophysical Research |volume=103 |issue=B12 |pages=29815–29828|doi-access=free }}</ref>

Oftentimes, potassium can replace the sodium characteristic in albite at amounts of up to 10%. When this is exceeded the mineral is then considered to be [[anorthoclase]].<ref>{{Cite web|url=https://www.minerals.net/mineral/albite.aspx|title=Anorthoclase|website=www.minerals.net}}</ref>

== Occurrence ==
<!-- [[Cleavelandite]] redirects to this section-->
It occurs in [[granitic]] and [[pegmatite]] masses (often as the variety '''cleavelandite'''),<ref>{{cite web |title=Cleavelandite |url=https://www.mindat.org/min-7688.html |website=www.mindat.org }}</ref> in some [[hydrothermal]] [[Vein (geology)|vein]] deposits, and forms part of the typical [[greenschist]] [[metamorphic facies]] for rocks of originally [[basalt]]ic composition. Minerals that albite is often considered associated with in occurrence include biotite, hornblende, orthoclase, muscovite and quartz.<ref>{{Cite web|url=https://www.mindat.org/min-96.html|title=Associated minerals|website=www.mindat.org}}</ref>

== Discovery ==
Albite was first reported in 1815 for an occurrence in Finnbo, [[Falun]], [[Dalarna]], [[Sweden]].<ref name=Mindat/>
{{stack|[[Image:Albite-70858.jpg|thumb|right|Albite from Italy]]}}
== Use ==
Albite is used as a [[gemstone]], albeit semiprecious. Albite is also used by geologists as it is identified as an important rock forming mineral. There is some industrial use for the mineral such as the manufacture of [[glass]] and ceramics.<ref>{{cite book|title=Loose Gemstone Guide – Secrets of the Gem Revealed|first=Pao|last=Nipperkin}}</ref><ref>{{Cite web|url=https://www.britannica.com/science/albite|title=Uses of albite|website=britannica.com|access-date=4 April 2019}}</ref>

One of the iridescent varieties of albite, discovered in 1925 near the [[White Sea]] coast by academician [[Alexander Fersman]], became widely known under the trade name [[belomorite]].<ref name="Memories">''[[Alexander Fersman]]''. «Memories of the Stone». — Moscow: Publishing House of the USSR Academy of Sciences, 1958.</ref>

==References==
{{Reflist}}

==External links==
{{Commons category|Albite}}
* [http://www.galleries.com/minerals/silicate/albite/albite.htm Mineral galleries]

{{Authority control}}

[[Category:Tectosilicates]]
[[Category:Feldspar]]
[[Category:Triclinic minerals]]
[[Category:Luminescent minerals]]
[[Category:Gemstones]]
[[Category:Minerals in space group 2]]