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Anorthite

Big Photo

Caspar quarry, Ettringer Bellerberg Mt. (Bellberg Mt.; Bellenberg Mt.; Billenberg Mt.; Boilenberg Mt.), Bellerberg volcano, Ettringen, Mayen, Eifel Mts, Rhineland-Palatinate, Germany
© Stephan Wolfsried

Show Anorthite Photos (27)
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)

About Crystal Atlas

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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)
Member of Group:
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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