Andalusite

Andalusite

Infobox mineral
name = Andalusite
category = mineral
boxwidth =
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imagesize =
caption = Dark, rod-like andalusite crystals in a light green cordierite schist matrix (writing pen shows size).
formula = Al2SiO5Gemological Institute of America, "GIA Gem Reference Guide" 1995, ISBN 0-87311-019-6]
molweight =
color = transparent to opaque brownish or yellowish green to orangy brown; may be pure green, brown, pink, violet (rare), and red
habit =
system = orthorhombic
twinning = lamellar
cleavage = distinct in one direction
fracture = uneven to conchoidal
mohs = 7 - 7.5
luster = vitreous
polish = vitreous
refractive = 1.634 - 1.643 (+/-.005)
opticalprop = double refractive, biaxial negative; "chiastolite" has anomalous aggregate reaction. Can also display chatoyancy.
birefringence = .007 - .013
dispersion = .016
pleochroism = Strong. Brownish to yellowish green and brownish orange to brownish red
fluorescence= inert in long wave, inert to moderate green to yellowish green in short wave
absorption =
streak =
gravity = 3.17 (+/- .04)
density =
melt =
fusibility =
diagnostic =
solubility =
diaphaneity =
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Andalusite is an aluminium nesosilicate mineral with the chemical formula Al2SiO5.

The variety chiastolite commonly contains dark inclusions of carbon or clay which form an "X" or a cross in section.

A clear variety first found in Andalusia, Spain can be cut into an interesting gemstone. [ [http://www.gemstone.org/gem-by-gem/english/andalusite.html "International Colored Gem Association: Anadalusite"] ] Faceted andalusite stones give a play of red, green, and yellow colors that resembles a muted form of iridescence, although the colors are actually the result of unusually strong pleochroism.

Occurrence

Andalusite is a common regional metamorphic mineral which forms under low pressure and moderate to high temperatures. Called Lapis Crucifer in ancient texts. The minerals kyanite and sillimanite are polymorphs of andalusite, each occurring under different temperature-pressure regimes and are therefore rarely found together in the same rock. Because of this the three minerals are a useful tool to help identify the pressure-temperature paths of the host rock in which they are found.

It was first reported from Andalucia, Spain in 1789.

Related minerals

* Kyanite
* Sillimanite
* Chiastolite

See also

* List of minerals

References

* [http://mineral.galleries.com/minerals/silicate/andalusi/andalusi.htm Mineral galleries]
* [http://webmineral.com/data/Andalusite.shtml Webmineral]
* [http://www.mindat.org/show.php?id=217&ld=1&pho= Mindat w/ locations]
*http://www.gemstone.org/gem-by-gem/english/andalusite.html

Notes


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Look at other dictionaries:

  • Andalusite — An da*lu site, n. (Min.) A silicate of aluminium, occurring usually in thick rhombic prisms, nearly square, of a grayish or pale reddish tint. It was first discovered in Andalusia, Spain. [1913 Webster] || …   The Collaborative International Dictionary of English

  • andalusite — [an΄də lo͞o′sīt΄] n. [after ANDALUSIA, where it was discovered] a very hard, orthorhombic silicate of aluminum, Al2SiO5, usually found in schist, slate, or other metamorphic rocks and used to make various high temperature materials and as a gem …   English World dictionary

  • Andalusite — Andalousite Andalousite Catégorie IX : silicates Andalousite Tyrol Autriche (7,4x6,2cm) …   Wikipédia en Français

  • andalusite — /an dl ooh suyt/, n. Mineral. an orthorhombic form of aluminum silicate, Al2SiO5, found in schistose rocks. [1830 40; named after ANDALUSIA, where it was first found; see ITE1] * * * ▪ mineral  (Al2SiO5), aluminum silicate mineral that occurs in… …   Universalium

  • andalusite — andalūzitas statusas T sritis chemija apibrėžtis Mineralas. formulė Al₂[O|SiO₄] atitikmenys: angl. andalusite rus. андалузит …   Chemijos terminų aiškinamasis žodynas

  • andalusite — noun Etymology: French andalousite, from Andalousie Andalusia, region in Spain Date: circa 1828 a mineral consisting of a silicate of aluminum usually in thick orthorhombic prisms of various colors …   New Collegiate Dictionary

  • andalusite — noun An aluminium nesosilicate mineral, AlSiO …   Wiktionary

  • andalusite — an·da·lu·sì·te s.f. TS mineral. silicato di alluminio cristallino, comune in alcune rocce metamorfiche {{line}} {{/line}} DATA: 1817. ETIMO: der. di Andalusia, v. anche andaluso, con 2 ite …   Dizionario italiano

  • andalusite — {{hw}}{{andalusite}}{{/hw}}s. f. (mineral.) Silicato d alluminio, in prismi opachi con inclusioni di carbone, diffuso in alcune rocce metamorfiche …   Enciclopedia di italiano

  • andalusite — pl.f. andalusiti …   Dizionario dei sinonimi e contrari

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