Muscovite
21062
224436732
2008-07-08T20:57:42Z
TDogg310
329397
{{Otheruses2|Muscovite}}
{{Infobox mineral
| name = Muscovite
| category = [[Mineral]] Species
| boxwidth =
| boxbgcolor =
| image = Muscovite2.jpg
| imagesize = 200px
| caption = Muscovite from a [[pegmatite]] outcrop along the [[Patapsco River]] in [[Baltimore County, Maryland|Baltimore County]], [[Maryland]].
| formula = KAl<sub>2</sub>(AlSi<sub>3</sub>O<sub>10</sub>)(F,OH)<sub>2</sub>
| molweight = 398.71 gm
| color = White, grey, silvery
| habit = massive to platy Crystaline
| system = Monoclinic - Prismatic
| twinning = common on the [310] less common on the {001}
| cleavage = Perfect on the {001}
| fracture = Micaeous
| tenacity = Elastic
| mohs = 2-2.5, 4
| luster = Vitreous
| polish =
| refractive = n<sub>α</sub> = 1.552 - 1.576 n<sub>β</sub> = 1.582 - 1.615 n<sub>γ</sub> = 1.587 - 1.618
| opticalprop = Biaxial
| birefringence = δ = 0.035 - 0.042
| dispersion = r > v weak
| pleochroism = weak when colored
| fluorescence= None
| absorption =
| streak = White
| gravity = 2.76 - 3
| density = 2.83 g/cm<sub>3</sub>
| melt = approximately 1320°C
| fusibility =
| diagnostic =
| solubility =
| diaphaneity = transparent or translucent
| other =
| references =<ref>[http://www.mindat.org/min-2815.html Muscovite: Muscovite mineral information and data<!-- Bot generated title -->]</ref><ref>[http://www.webmineral.com/data/Muscovite.shtml Muscovite Mineral Data<!-- Bot generated title -->]</ref>
}}
'''Muscovite''' (also known as '''Common [[mica]]''', '''Isinglass''', or '''[[Potash]] mica'''<ref>[http://www.britannica.com/eb/article-9054407/muscovite Encyclopædia Britannica]</ref>) is a [[Silicate minerals|phyllosilicate]] [[mineral]] of [[aluminium]] and [[potassium]] with formula: [[potassium|K]][[aluminum|Al]]<sub>2</sub>(Al[[silicon|Si]]<sub>3</sub>[[oxygen|O]]<sub>10</sub>)([[fluorine|F]],O[[hydrogen|H]])<sub>2</sub>. It has a highly perfect basal cleavage yielding remarkably thin laminae (sheets), which are often highly elastic. Sheets of muscovite 5 metres by 3 metres have been found in Nellore, India.<ref>''The Complete Encyclopedia of Minerals'' by P. Korbel and M. Novak</ref>
Muscovite melts at approximately 1320°C, has a [[Mohs hardness]] of 2 - 2.25 parallel to the [001] face, 4 perpendicular to the [001] and a [[specific gravity]] of 2.76 - 3. It can be colorless or tinted through [[gray (color)|grays]], [[brown|browns]], [[green|greens]], [[yellow|yellows]], or (rarely) [[violet (color)|violet]] or [[red]], and can be transparent or translucent. The green, [[chromium]]-rich variety is called '''fuchsite'''.
Muscovite is the most common mica, found in [[granite|granites]], [[pegmatite|pegmatites]], [[gneiss|gneisses]] and [[schist|schists]], and as a contact [[metamorphic rock]] or as a secondary [[mineral]] resulting from the alteration of [[topaz]], [[feldspar]], [[kyanite]], etc. In pegmatites, it is often found in immense sheets that are commercially valuable. Muscovite is in demand for the manufacture of [[fireproofing]] and insulating materials and to some extent as a [[lubricant]].
The name of muscovite comes from Muscovy-glass, a name formerly used for the mineral because of its use in [[Russia]] for [[window|windows]]. It is [[anisotropic]], and has high [[birefringence]]. Its crystal system is [[monoclinic]].
== See also ==
* [[List of minerals]]
== References ==
*[http://rruff.geo.arizona.edu/doclib/hom/muscovite.pdf Mineral Handbook]
*[http://www.mindat.org/min-2815.html Mindat]
*[http://webmineral.com/data/Muscovite.shtml Webmineral]
<references/>
{{Commonscat|Muscovite}}
{{mineral-stub}}
[[Category: Potassium minerals]]
[[Category: Aluminium minerals]]
[[Category: Hydroxide minerals]]
[[Category: Phyllosilicates]]
[[Category: Mica group]]
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