Infobox mineral
name = Anorthite
category = Feldspar mineral
boxwidth =
boxbgcolor =

imagesize =
caption = Anorthite from Japan
formula = CaAl2Si2O8
molweight =
color = White, grayish, reddish
habit = Anhedral to subhedral granular
system = Triclinic
twinning = Common
cleavage = Perfect [001] good [010]
fracture = Uneven to concoidal
tenacity = Brittle
mohs = 6
luster = Vitreous
polish =
refractive = nα = 1.573 - 1.577 nβ = 1.580 - 1.585 nγ = 1.585 - 1.590
opticalprop = Biaxial (-), 2V 78° to 83°
birefringence = δ = 0.012 - 0.013
dispersion =
pleochroism =
absorption =
streak =
gravity = 2.72 - 2.75
density =
melt =
fusibility =
diagnostic =
solubility =
diaphaneity = Transparent to translucent
other =
references = Handbook of Mineralogy] [ Mindat] Webmineral]

Anorthite is a compositional variety of plagioclase feldspar. Plagioclase is an abundant mineral in the Earth's crust. The formula of pure anorthite is CaAl2Si2O8.


Anorthite is the calcium-rich endmember of the plagioclase solid solution series, the other endmember being albite, NaAlSi3O8. Anorthite also refers to plagioclase compositions with more than 90 molecular percent of the anorthite endmember.


Anorthite is a rare compositional variety of plagioclase. It occurs in mafic igneous. It also occurs in granulite facies metamorphic rocks, in metamorphosed carbonate rocks and corundum deposits. Its type localities are Monte Somma and Valle di Fassa, Italy. It was first described in 1823.

It also makes up much of the lunar highlands. Anorthite was discovered in samples from comet Wild 2, and the mineral is an important constituent of Ca-Al-rich inclusions in rare varieties of chondritic meteorites.

See also

*List of minerals
*In-Situ Resource Utilization


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Look at other dictionaries:

  • Anorthite — Anorthite[1] Catégorie IX : silicates[2] …   Wikipédia en Français

  • anorthite — ● anorthite nom féminin (allemand Anorthit, du grec orthos, droit) Minéral constituant le pôle calcique de la série des plagioclases (CaAl2Si2O8), triclinique. ⇒ANORTHITE, subst. fém. MINÉR. Silicate d aluminium et de calcium, appartenant à la… …   Encyclopédie Universelle

  • Anorthite — A*nor thite, n. [Gr. an priv. + ? straight (? sc. ? right angle); not in a right angle.] A mineral of the feldspar family, commonly occurring in small glassy crystals, also a constituent of some igneous rocks. It is a lime feldspar. See… …   The Collaborative International Dictionary of English

  • anorthite — [an ôr′thīt΄] n. [< Gr an , not + orthos, straight (see ORTHO ) + ITE1] a white or grayish variety of plagioclase, CaAl2Si2O8, found in basic igneous rocks anorthitic [an ôr′thit′ik] adj …   English World dictionary

  • anorthite — anorthitic /an awr thit ik/, adj. /an awr thuyt/, n. Mineral. a white or gray feldspar mineral, CaAl2Si2O8, calcic plagioclase. [1825 35; AN 1 + ORTH + ITE1] * * * Feldspar mineral, calcium aluminosilicate (CaAl2Si2O8), that occurs as white or… …   Universalium

  • anorthite — noun A plagioclase feldspar, the final member of the Albite Anorthite solid solution series. Anorthite is very rare on Earth, but abundant in moon rocks. This is because Anorthite weathers rapidly to clay minerals under atmospheric conditions.… …   Wiktionary

  • anorthite — anortitas statusas T sritis chemija apibrėžtis Mineralas. formulė Ca[Al₂Si₂O₈] atitikmenys: angl. anorthite rus. анортит …   Chemijos terminų aiškinamasis žodynas

  • anorthite — noun Etymology: French, from a + Greek orthos straight Date: 1833 a white, grayish, or reddish feldspar occurring in many igneous rocks • anorthitic adjective …   New Collegiate Dictionary

  • anorthite — [ə nɔ:θʌɪt] noun a calcium rich mineral of the feldspar group, typically white. Origin C19: from an 1 + Gk orthos straight + ite1 …   English new terms dictionary

  • anorthite — an·or·thite …   English syllables

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