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Colourless, reddish grey, white
6 - 6½
Specific Gravity:
2.74 - 2.76
Crystal System:
Member of:
Named in 1823 by Gustav Rose from the Greek αν and oρθός, "not right angle" or "oblique", in allusion to the oblique triclinic form of the crystals.
Feldspar Group.

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

High- and low-temperature structural modifications exist.

Visit for gemological information about Anorthite.

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Classification of AnorthiteHide

Approved, 'Grandfathered' (first described prior to 1959)

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H2O
A : Tektosilicates without additional non-tetrahedral anions

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

Physical Properties of AnorthiteHide

Transparent, Translucent
Colourless, reddish grey, white
6 - 6½ on Mohs scale
Perfect on {001}, less so on {010}, imperfect on {110}
Irregular/Uneven, Conchoidal
2.74 - 2.76 g/cm3 (Measured)    2.76 g/cm3 (Calculated)

Optical Data of AnorthiteHide

Biaxial (-)
RI values:
nα = 1.573 - 1.577 nβ = 1.580 - 1.585 nγ = 1.585 - 1.590
Measured: 78° to 83°, Calculated: 78°
Max Birefringence:
δ = 0.012 - 0.013
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
r < v weak

Chemical Properties of AnorthiteHide

IMA Formula:
Common Impurities:

Crystallography of AnorthiteHide

Crystal System:
Class (H-M):
1 - Pinacoidal
Space Group:
Cell Parameters:
a = 8.1768 Å, b = 12.8768 Å, c = 14.169 Å
α = 93.17°, β = 115.85°, γ = 92.22°
a:b:c = 0.635 : 1 : 1.1
Unit Cell V:
1,337.25 ų (Calculated from Unit Cell)
Commonly short, prismatic, lamellar, coarse-granular, massive
Commonly polysynthetic on albite law, pericline, Carlsbad, Manebach and Baveno twinning.
Low modification; non-standard unit cell (reduced cell: 8.18, 12.87, 12.90 A, 85.8, 81.1, 88.7°)

Crystallographic forms of AnorthiteHide

Crystal Atlas:
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Anorthite no.89 - Goldschmidt (1913-1926)
Anorthite no.126 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by

Edge Lines | Miller Indicies | Axes

Opaque | Translucent | Transparent

Along a-axis | Along b-axis | Along c-axis | Start rotation | Stop rotation

X-Ray Powder DiffractionHide

Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Type Occurrence of AnorthiteHide

Synonyms of AnorthiteHide

Other Language Names for AnorthiteHide

Varieties of AnorthiteHide

Barium-Anorthite (of Nockolds and Zies)A barian anorthite with 3.5% BaO.
Originally described from Broken Hill, Yancowinna Co., New South Wales, Australia.
BytowniteA plagioclase feldspar with an albite : anorthite molar ratio ranging from 10 : 90 to 30 : 70.

The original material, a greenish-white substance, was found in a boulder near Bytown (now Ottawa), and later shown to be a mixture (Robert A. A. Johnston, 1...
LindsayiteAn altered Anorthite

Relationship of Anorthite to other SpeciesHide

Member of:
Other Members of this group:
AlbiteNa(AlSi3O8)Tric. 1
Buddingtonite(NH4)(AlSi3)O8Mon. 2 : P21
CelsianBa(Al2Si2O8)Mon. 2/m
DmisteinbergiteCa(Al2Si2O8)Hex. 6/mmm (6/m 2/m 2/m) : P6/mmm
FilatoviteK(Al,Zn)2(As,Si)2O8Mon. 2/m
HexacelsianBaAl2Si2O8Hex. 6/mmm (6/m 2/m 2/m) : P63/mcm
KokchetaviteK(AlSi3O8)Hex. 6/mmm (6/m 2/m 2/m) : P6/mmm
KumdykoliteNa(AlSi3O8)Orth. mmm (2/m 2/m 2/m) : Pnnm
MicroclineK(AlSi3O8)Tric. 1
OrthoclaseK(AlSi3O8)Mon. 2/m : B2/m
SanidineK(AlSi3O8)Mon. 2/m : B2/m
SunstoneA variety of feldspar (microcline or oligoclase, more rarely labradorite) that has schiller, ...
Forms a series with:

Common AssociatesHide

Associated Minerals Based on Photo Data:
Hessonite20 photos of Anorthite associated with Hessonite on
Clinozoisite20 photos of Anorthite associated with Clinozoisite on
Vesuvianite15 photos of Anorthite associated with Vesuvianite on
Ruby10 photos of Anorthite associated with Ruby on
Allophane10 photos of Anorthite associated with Allophane on
Pargasite8 photos of Anorthite associated with Pargasite on
Quartz8 photos of Anorthite associated with Quartz on
Stilbite8 photos of Anorthite associated with Stilbite on
Chabazite7 photos of Anorthite associated with Chabazite on
Olivine6 photos of Anorthite associated with Olivine on

Related Minerals - Nickel-Strunz GroupingHide

9.FA.05KalsiliteKAlSiO4Hex. 6 2 2 : P63 2 2
9.FA.05Nepheline(Na,K)AlSiO4Hex. 6 : P63
9.FA.05Panunzite(K,Na)AlSiO4Hex. 6 : P63
9.FA.05Yoshiokaite(Ca,Na)[Al(Al,Si)O4]Trig. 3 : P3
9.FA.10MalinkoiteNaBSiO4Hex. 6 : P63
9.FA.15VirgiliteLiAlSi2O6Hex. 6 2 2 : P62 2 2
9.FA.25LisitsyniteKBSi2O6Orth. 2 2 2 : P2 2 2
9.FA.30Buddingtonite(NH4)(AlSi3)O8Mon. 2 : P21
9.FA.30CelsianBa(Al2Si2O8)Mon. 2/m
9.FA.30MicroclineK(AlSi3O8)Tric. 1
9.FA.30OrthoclaseK(AlSi3O8)Mon. 2/m : B2/m
9.FA.30SanidineK(AlSi3O8)Mon. 2/m : B2/m
9.FA.30MonalbiteNaAlSi3O8Mon. 2/m : B2/m
9.FA.35AlbiteNa(AlSi3O8)Tric. 1
9.FA.45KumdykoliteNa(AlSi3O8)Orth. mmm (2/m 2/m 2/m) : Pnnm
9.FA.65DanburiteCaB2Si2O8Orth. mmm (2/m 2/m 2/m)
9.FA.65MaleeviteBaB2Si2O8Orth. mmm (2/m 2/m 2/m) : Pnma
9.FA.70Lingunite(Na,Ca)AlSi3O8Tet. 4/m : I4/m
9.FA.75KokchetaviteK(AlSi3O8)Hex. 6/mmm (6/m 2/m 2/m) : P6/mmm

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

16.9.1GehleniteCa2Al(AlSiO7)Tet. 4 2m : P4 21m
16.9.3Yoshiokaite(Ca,Na)[Al(Al,Si)O4]Trig. 3 : P3
16.9.5DmisteinbergiteCa(Al2Si2O8)Hex. 6/mmm (6/m 2/m 2/m) : P6/mmm
16.9.6GrossularCa3Al2(SiO4)3Iso. m3m (4/m 3 2/m) : Ia3d
16.9.8Zoisite{Ca2}{Al3}(Si2O7)(SiO4)O(OH)Orth. mmm (2/m 2/m 2/m) : Pnma
16.9.9Clinozoisite{Ca2}{Al3}(Si2O7)(SiO4)O(OH)Mon. 2/m : P21/m
16.9.10PrehniteCa2Al2Si3O10(OH)2Orth. mm2
16.9.12BicchuliteCa2(Al2SiO6)(OH)2Iso. 4 3m : I4 3m
16.9.14ChantaliteCaAl2(SiO4)(OH)4Tet. 4/m : I41/a
16.9.18LawsoniteCaAl2(Si2O7)(OH)2 · H2OOrth. mmm (2/m 2/m 2/m) : Cmcm
16.9.19ParthéiteCa2(Si4Al4) O15 (OH)2•4H2OMon. 2/m : B2/b
16.9.20WairakiteCa(Al2Si4O12) · 2H2OMon. 2/m
16.9.21VertumniteCa4Al4Si4O6(OH)24 · 3H2OMon. 2/m : P21/m
16.9.22ScoleciteCaAl2Si3O10 · 3H2OMon. m : Bb
16.9.23LaumontiteCaAl2Si4O12 · 4H2OMon. 2/m : B2/m
16.9.24YugawaraliteCaAl2Si6O16 · 4H2OMon.
16.9.25Gismondine-CaCaAl2Si2O8 · 4H2O
16.9.26EpistilbiteCaAl2Si6O16 · 5H2OMon.
16.9.27GoosecreekiteCa[Al2Si6O16] · 5H2OMon.
16.9.28CowlesiteCaAl2Si3O10 · 6H2OOrth.
16.9.30StelleriteCa4(Si28Al8)O72 · 28H2OOrth. mmm (2/m 2/m 2/m) : Fmmm
16.9.31SträtlingiteCa2Al2SiO7 · 8H2OTrig.
16.9.32AmstalliteCaAl(Si,Al)4O8(OH)4 · (H2O,Cl)Mon. 2/m : B2/b

Other InformationHide

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

Anorthite in petrologyHide

References for AnorthiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Rose, G. (1823) Über den Feldspat, Albit, Labradorit und Anorthit. Annalen der Physik und Chemie: 73/NF-43: 173-208.
Rose, M.G. (1824) On felspar, albite, labrador, and anorthite. The Annals of Philosophy: 7: 49-59.
Osborn, E.F. (1942) The system CaSiO3-diopside-anorthite. American Journal of Science, 240: 11: 751-788.
Kempster, C.J.E., Megaw, H.D., Radoslovich, E.W. (1962) The structure of anorthite CaAl2Si2O8. I. Structure analysis. Acta Crystallographica: 15: 1005-1017.
Megaw, H.D., Kempster, C.J.E., Radoslovich, E.W. (1962) The structure of anorthite CaAl2Si2O8. II. Description and Discussion. Acta Crystallographica: 15: 1017-1035.
Bambauer, H.U., Corlett, M., Eberhard, E., Viswanathan, K. (1967) Diagrams for the determination of plagioclases using X-ray powder methods (Part III of laboratory investigations of plagioclases). Schweizerische Mineralogische und Petrographische Mitteilungen: 47: 333-349.
Stewart, D.B. (1967) Four-phase curve in the system CaAl2Si2O8-SiO2-H2O between 1 and 10 kilobars. Schweizerische Mineralogische und Petrographische Mitteilungen: 47: 35-59.
Nager, H.E., Hoffmann, W., Nissen, H.U. (1969) Die Mischreihe (Ca,Sr)[Al2Si2O8]. Naturwissenschaften: 56: 136-136.
Wainwright, J.E., Starkey, J. (1971) A refinement of the structure of anorthite. Zeitschrift für Kristallographie: 133: 75-84.
Richet, P., Bottinga, Y. (1984) Anorthite, andesine, wollastonite, diopside, cordierite, and pyrope thermodynamics of melting, glass transitions, and properties of the amorphous phases. Earth and Planetary Science Letters: 67: 415-432.
Wenk, H.R., Kroll, H. (1984) Analysis of P-1, I-1, and C-1 plagioclase structures. Bulletin de Minéralogie: 107: 467-487.
Matson, D.W., Sharma, S.K., Philpotts, J.A. (1986) Raman-spectra of some tectosilicates and of glasses along the orthoclase-anorthite and nepheline-anorthite joins. American Mineralogist: 71: 694-704.
Redfern, S.A.T., 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., 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., 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., Ghose, S., 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., 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., 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.
Chernosky, J.V., Berman, R.G. (1991) Experimental reversal of the equilibrium andalusite + calcite + quartz = anorthite + CO2. The Canadian Mineralogist: 29: 791-802.
Mernagh, T.P. (1991) Use of the laser Raman microprobe for discrimination amongst feldspar minerals. Journal of Raman Spectroscopy: 22: 453-457.
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., Webb, S.L. (1992) 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., Webb, S.L. (1992) Temperature-dependent thermal expansivities of silicate melts: The system anorthite-diopside. Geochimica et Cosmochimica Acta: 56: 689-699.
Redfern, S.A.T., 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.
Anthony, J.W., Bideaux, R.A., Bladh, K.W., Nichols, M.C. (1995) Handbook of Mineralogy, Volume II. Silica, Silicates. Mineral Data Publishing, Tucson, AZ, 904pp., 2 sub-volumes: 33.
Courtial, P., Téqui, C., 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.
Le Parc, R., Champagnon, B., Dianoux, J., Jarry, P., Martinez, V. (2003) Anorthite and CaAl2Si2O8 glass: low frequency Raman spectroscopy and neutron scattering. Journal of Non-Crystalline Solids: 323: 155-161.
Freeman, J.J., Wang, A., Kuebler, K.E., Jolliff, B.L., Haskin, L.A. (2008) Characterization of natural feldspars by Raman spectroscopy for future planetary exploration. The Canadian Mineralogist: 46: 1477-1500.
Parsons, I. (2010) Feldspars defined and described: a pair of posters published by the Mineralogical Society. Sources and supporting information. Mineralogical Magazine: 74: 529-551.
Kaercher, P., Militzer, B., Wenk, H.R. (2014) Ab initio calculations of elastic constants of plagioclase feldspars. American Mineralogist: 99: 2344-2352.
Brown, J.M., Angel, R.J., Ross, N.L. (2016) Elasticity of plagioclase feldspars. Journal of Geophysical Research: 121, 1-13.

Internet Links for AnorthiteHide

Localities for AnorthiteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListShow

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