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Anorthite

Big Photo

Caspar quarry, Bellerberg volcano, Ettringen, Mayen, Eifel Mts, Rhineland-Palatinate, Germany
© Stephan Wolfsried

Show Anorthite Photos (28)
Formula:
Ca[Al
 
2
Si
 
2
O
 
8
]
System:TriclinicColour:Colourless, reddish ...
Hardness:6 - 6½
Name:From the Greek for oblique, for being triclinic.
Dimorph of:Svyatoslavite


Feldspar Group.

Ca-rich end member of the Albite-Anorthite Series.

High- and low-temperature structural modifications exist.

Classification of Anorthite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:8/J.07-70
Nickel-Strunz 10th (pending) edition ID:9.FA.35

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H2O
A : Tektosilicates without additional non-tetrahedral anions
Hey's CIM Ref.:16.9.2

16 : Silicates Containing Aluminum and other Metals
9 : Aluminosilicates of Ca
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Type Occurrence of Anorthite

Type Locality:Monte Somma, Somma-Vesuvius Complex, Naples Province, Campania, Italy
Year of Discovery:1823

Occurrences of Anorthite

Geological Setting:Mafic plutonic rocks

Physical Properties of Anorthite

Lustre:Vitreous
Diaphaneity (Transparency):Transparent, Translucent
Colour:Colourless, reddish grey, white
Streak:White
Hardness (Mohs):6 - 6½
Tenacity:Brittle
Cleavage:Perfect
Perfect on {001}, less so on {010}, imperfect on {110}
Fracture:Irregular/Uneven, Conchoidal
Density (measured):2.74 - 2.76 g/cm3
Density (calculated):2.76 g/cm3

Crystallography of Anorthite

Crystal System:Triclinic
Class (H-M):1 - Pinacoidal
Space Group:P1
Cell Parameters:a = 8.1768Å, b = 12.8768Å, c = 14.169Å
α = 93.17°, β = 115.85°, γ = 92.22°
Ratio:a:b:c = 0.635 : 1 : 1.1
Unit Cell Volume:V 1,337.25 ų (Calculated from Unit Cell)
Z:8
Morphology:Commonly short, prismatic, lamellar, coarse granular, massive
Twinning:Commonly polysynthetic on albite law, pericline, Carlsbad, Manebach and Baveno twinning.
Comment:Low modification; non-standard unit cell (reduced cell: 8.18, 12.87, 12.90 A, 85.8, 81.1, 88.7°)
Crystal Atlas:
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Anorthite no.89 - Goldschmidt (1913-1926)
Anorthite no.126 - Goldschmidt (1913-1926)

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X-Ray Powder Diffraction:
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Radiation - Copper Kα
Data Set:
Horizontal Axis: ° to ° Vertical Axis: % Source Data: Filtered Data: Peaks:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Optical Data of Anorthite

Type:Biaxial (-)
RI values: nα = 1.573 - 1.577 nβ = 1.580 - 1.585 nγ = 1.585 - 1.590
2V:Measured: 78° to 83°, Calculated: 78°
Maximum Birefringence:δ = 0.012 - 0.013

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Moderate
Dispersion:r < v weak

Chemical Properties of Anorthite

Formula:
Ca[Al
 
2
Si
 
2
O
 
8
]
Essential elements:Al, Ca, O, Si
All elements listed in formula:Al, Ca, O, Si
Common Impurities:Ti,Fe,Na,K

Relationship of Anorthite to other Species

Series:Forms a series with Albite (see here)
Related to:
  • Feldspar Group
    • Related Minerals - Nickel-Strunz Grouping):

    - +
    9.FA.05Kaliophilite
    K[AlSiO
     
    4
    		]
    9.FA.05Kalsilite
    K[AlSiO
     
    4
    		]
    9.FA.05Nepheline
    (Na,K)[AlSiO
     
    4
    		]
    9.FA.05Panunzite
    (Na,K)[AlSiO
     
    4
    		]
    9.FA.05Trikalsilite
    (Na,K)[AlSiO
     
    4
    		]
    9.FA.05Yoshiokaite
    (Ca,Na)[Al(Al,Si)O
     
    4
    		]
    9.FA.05Megakalsilite
    KAlSiO
     
    4
    9.FA.10Malinkoite
    NaBSiO
     
    4
    9.FA.15Virgilite
    LiAlSi
     
    2
    		O
     
    6
    9.FA.25Lisitsynite
    KBSi
     
    2
    		O
     
    6
    9.FA.30Adularia
    KAlSi
     
    3
    		O
     
    8
    9.FA.30Anorthoclase
    (Na,K)[AlSi
     
    3
    		O
     
    8
    		]
    9.FA.30Buddingtonite
    (NH
     
    4
    		)[AlSi
     
    3
    		O
     
    8
    		]
    9.FA.30Celsian
    Ba[Al
     
    2
    		Si
     
    2
    		O
     
    8
    		]
    9.FA.30Hyalophane
    (K,Ba)[Al(Si,Al)Si
     
    2
    		O
     
    8
    		]
    9.FA.30Microcline
    K[AlSi
     
    3
    		O
     
    8
    		]
    9.FA.30Orthoclase
    K[AlSi
     
    3
    		O
     
    8
    		]
    9.FA.30Sanidine
    K[AlSi
     
    3
    		O
     
    8
    		]
    9.FA.30Rubicline
    (Rb,K)[AlSi
     
    3
    		O
     
    8
    		]
    9.FA.30Monalbite
    Na[AlSi
     
    3
    		O
     
    8
    		]
    9.FA.35Albite
    Na[AlSi
     
    3
    		O
     
    8
    		]
    9.FA.35Andesine
    (Na,Ca)[Al(Si,Al)Si
     
    2
    		O
     
    8
    		]
    9.FA.35Bytownite
    (Ca,Na)[Al(Al,Si)Si
     
    2
    		O
     
    8
    		]
    9.FA.35Labradorite
    (Ca,Na)[Al(Al,Si)Si
     
    2
    		O
     
    8
    		]
    9.FA.35Oligoclase
    (Na,Ca)[Al(Si,Al)Si
     
    2
    		O
     
    8
    		]
    9.FA.35Reedmergnerite
    Na[BSi
     
    3
    		O
     
    8
    		]
    9.FA.40Paracelsian
    Ba[Al
     
    2
    		Si
     
    2
    		O
     
    8
    		]
    9.FA.45Svyatoslavite
    Ca[Al
     
    2
    		Si
     
    2
    		O
     
    8
    		]
    9.FA.45Kumdykolite
    NaAlSi
     
    3
    		O
     
    8
    9.FA.50Slawsonite
    (Sr,Ca)[Al
     
    2
    		Si
     
    2
    		O
     
    8
    		]
    9.FA.55Lisetite
    CaNa
     
    2
    		Al
     
    4
    		Si
     
    4
    		O
     
    16
    9.FA.60Banalsite
    BaNa
     
    2
    		[Al
     
    2
    		Si
     
    2
    		O
     
    8
    		]
     
    2
    9.FA.60Stronalsite
    SrNa
     
    2
    		[Al
     
    2
    		Si
     
    2
    		O
     
    8
    		]
     
    2
    9.FA.65Danburite
    CaB
     
    2
    		Si
     
    2
    		O
     
    8
    9.FA.65Maleevite
    BaB
     
    2
    		Si
     
    2
    		O
     
    8
    9.FA.65Pekovite
    SrB
     
    2
    		Si
     
    2
    		O
     
    8
    9.FA.70Lingunite
    (Na,Ca)AlSi
     
    3
    		O
     
    8
    9.FA.75Kokchetavite
    KAlSi
     
    3
    		O
     
    8
    Related Minerals - Hey's Index Grouping:

    - +
    16.9.1Gehlenite
    Ca
     
    2
    		Al[AlSiO
     
    7
    		]
    16.9.3Yoshiokaite
    (Ca,Na)[Al(Al,Si)O
     
    4
    		]
    16.9.4Svyatoslavite
    Ca[Al
     
    2
    		Si
     
    2
    		O
     
    8
    		]
    16.9.5Dmisteinbergite
    Ca[Al
     
    2
    		Si
     
    2
    		O
     
    8
    		]
    16.9.6Grossular
    Ca
     
    3
    		Al
     
    2
    		[SiO
     
    4
    		]
     
    3
    16.9.7Vuagnatite
    CaAl[OH|SiO
     
    4
    		]
    16.9.8Zoisite
    {Ca
     
    2
    		}{Al
     
    3
    		}[O|OH|SiO
     
    4
    		|Si
     
    2
    		O
     
    7
    		]
    16.9.9Clinozoisite
    {Ca
     
    2
    		}{Al
     
    3
    		}[O|OH|SiO
     
    4
    		|Si
     
    2
    		O
     
    7
    		]
    16.9.10Prehnite
    Ca
     
    2
    		Al
     
    2
    		Si
     
    3
    		O
     
    12
    		(OH)
    16.9.11Kamaishilite
    Ca
     
    2
    		[(OH)
     
    2
    		|Al
     
    2
    		SiO
     
    6
    		]
    16.9.12Bicchulite
    Ca
     
    2
    		[(OH)
     
    2
    		|Al
     
    2
    		SiO
     
    6
    		]
    16.9.13Margarite
    CaAl
     
    2
    		[(OH)
     
    2
    		|Al
     
    2
    		Si
     
    2
    		O
     
    10
    		]
    16.9.14Chantalite
    CaAl
     
    2
    		[(OH)
     
    4
    		|SiO
     
    4
    		]
    16.9.15Cebollite
    Ca
     
    5
    		Al
     
    2
    		Si
     
    3
    		O
     
    12
    		(OH)
     
    4
    		 or near
    16.9.17Katoite
    Ca
     
    3
    		Al
     
    2
    		[(OH)
     
    8-6
    		|(SiO
     
    4
    		)
     
    1-1.5
    		]
    16.9.18Lawsonite
    CaAl
     
    2
    		[(OH)
     
    2
    		|Si
     
    2
    		O
     
    7
    		] · H
     
    2
    		O
    16.9.19Parthéite
    CaAl
     
    2
    		Si
     
    2
    		O
     
    8
    		·2H
     
    2
    		O
    16.9.20Wairakite
    Ca[Al
     
    2
    		Si
     
    4
    		O
     
    12
    		] · 2H
     
    2
    		O
    16.9.21Vertumnite
    Ca
     
    4
    		Al
     
    4
    		Si
     
    4
    		O
     
    6
    		(OH)
     
    24
    		·3H
     
    2
    		O
    16.9.22Scolecite
    Ca[Al
     
    2
    		Si
     
    3
    		O
     
    10
    		] · 3H
     
    2
    		O
    16.9.23Laumontite
    CaAl
     
    2
    		Si
     
    4
    		O
     
    12
    		·4H
     
    2
    		O
    16.9.24Yugawaralite
    CaAl
     
    2
    		Si
     
    6
    		O
     
    16
    		·4H
     
    2
    		O
    16.9.25Gismondine-Ca
    CaAl
     
    2
    		Si
     
    2
    		O
     
    8
    		·4H
     
    2
    		O
    16.9.26Epistilbite
    CaAl
     
    2
    		Si
     
    6
    		O
     
    16
    		·5H
     
    2
    		O
    16.9.27Goosecreekite
    Ca[Al
     
    2
    		Si
     
    6
    		O
     
    16
    		] · 5H
     
    2
    		O
    16.9.28Cowlesite
    CaAl
     
    2
    		Si
     
    3
    		O
     
    10
    		·6H
     
    2
    		O
    16.9.30Stellerite
    Ca[Al
     
    2
    		Si
     
    7
    		O
     
    18
    		] · 7H
     
    2
    		O
    16.9.31Strätlingite
    Ca
     
    2
    		Al
     
    2
    		SiO
     
    7
    		·8H
     
    2
    		O
    16.9.32Amstallite
    CaAl(Si,Al)
     
    4
    		O
     
    8
    		(OH)
     
    4
    		·(H
     
    2
    		O,Cl)

    Other Names for Anorthite

    Synonyms:
    AmphodeliteAnorthoîteBarsoviteBeffaniteBeffonite
    BiotineCalciclaseCalcium FeldsparChristianiteCyclopite
    DidymoliteIndianiteLatrobiteLepoliteLime-Feldspar
    Thiorsauite
    Other Languages:
    Bosnian (Latin Script):Anortit
    Dutch:Anorthiet
    Finnish:Anortiitti
    German:Anorthit
    Amphodelit
    Anorthoît
    Barsovit
    Beffanit
    Beffonit
    Cyclopit
    Lepolit
    Hebrew:אנורתיט
    Italian:Anortite
    Japanese:灰長石
    Lithuanian:Anortitas
    Norwegian (Bokmål):Anortitt
    Polish:Anortyt
    Portuguese:Anortita
    Russian:Анортит
    Serbian (Cyrillic Script):Анортит
    Spanish:Anortita
    Amphodelita
    Anorthita
    Anorthoîta
    Barsovita
    Beffanita
    Beffonita
    Cyclopita
    Lepolita
    Swedish:Anortit
    Ukrainian:Анортит
    Varieties:
    Barium-Anorthite (of Nockolds and Zies)BytowniteLabradoriteLindsayiteLynx Eye

    Other Information

    Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

    References for Anorthite

    Reference List:Rose. G. (1823): Über den Feldspat, Albit, Labradorit und Anorthit, Annalen der Physik und Chemie, Vol. 73/NF-43, 175-208.

    Acta Crystallographica: 15: 117-135.

    Richet, P. and Bottinga, Y. (1984b) Anorthite, andesine, wollastonite, dopside, cordierite, and pyrope thermodynamics of melting, glass transitions, and properties of the amorphous phases. Earth and Planetary Science Letters: 67: 415-432.

    Redfern, S.A.T. and Salje, E. (1987), Thermodynamics of plagioclase II: temperature evolution of the spontaneous strain at the I1‾ ↔ P1‾ phase transition in anorthite. Physics and Chemistry of Minerals: 14: 189-195.

    Salje, E. (1987), Thermodynamics of plagioclase I: theory of the I1‾ - P1‾ phase transition in anorthite and Ca-rich plagioclases. Physics and Chemistry of Minerals: 14: 181-188.

    Angel, R.J. (1988), High-pressure structure of anorthite. American Mineralogist: 73: 1114-1119.

    Ghose, S., Van Tendeloo, G., and Amelinkx, S. (1988), Dynamics of a second-order phase transition: P1‾ to I1‾ phase transition in anorthite, CaAl2Si2O8. Science: 242: 1539-1541.

    Angel, R.J., Redfern, S.A.T., and Ross, N.L. (1989), Spontaneous strain below the I1‾ - P1‾ transition in anorthite at pressure. Physics and Chemistry of Minerals: 16: 539-544.

    Van Tendeloo, G., ose, S., and Amelinckx, S. (1989) A dynamical model for the P1‾ - I1‾ phase transition in anorthite, CaAl2Si2O8 I: Evidence from electron microscopy. Physics and Chemistry of Minerals: 16: 311-319.

    Angel, R.J., Carpenter, M.A., and Finger, L.W. (1990), Structural variation associated with compositional variation and order-disorder behaviour in anorthite-rich feldspars. American Mineralogist: 75: 150-162.

    Carpenter, M.A., Angel, R.J., and Finger, L.W. (1990), Calibration of Al/Si order variations in anorthite. Contributions to Mineralogy and Petrology: 104: 471-480.

    Carpenter, M.A. (1991), Mechanisms and kinetics of Al-Si ordering in anorthite: I. Incommensurate structure and domain coarsening: American Mineralogist: 76: 1110-1119.

    Angel, R.J. (1992), Order-disorder and the high-pressure P1‾-I1‾ transition in anorthite. American Mineralogist: 77: 923-929.

    Knoche, R., Dingwell, D.B., and Webb, S.L. (1992a) Non-linear temperature dependence of liquid volumes in the system albite-anorthite-diopside. Contributions to Mineralogy and Petrology: 111: 61-73.

    Knoche, R., Dingwell, D.B., and Webb, S.L. (1992b) Temperature-dependent thermal expansivities of silicate melts: The system anorthite-diopside. Geochimica et Cosmochimica Acta: 56: 689-699.

    Redfern, S.A.T. and Salje, E. (1992), Microscopic dynamic and macroscopic thermodynamic character of the I1‾ - P1‾ phase transition in anorthite Physics and Chemistry of Minerals: 18: 526-533.

    Courtial, P., Téqui, C., and Richet, P. (2000) Thermodynamics of diopside, anorthite, pseudowollastonite, CaMgGeO4 olivine, and åkermanite up to near the melting point. Physics and Chemistry of Minerals: 27: 242-250.

    Anthony, J.W., Bideaux, R.A., Bladh, K.W., and Nichols, M.C. (1995) Handbook of Mineralogy, Volume II. Silica, Silicates. Mineral Data Publishing, Tucson, AZ, 904pp., 2 sub-volumes: 33.

    Internet Links for Anorthite

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    Localities for Anorthite

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