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Anorthite

A valid IMA mineral species - grandfathered
This page kindly sponsored by Robert M. Hazen
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About AnorthiteHide

Formula:
Ca(Al2Si2O8)
Colour:
Colourless, reddish grey, white
Lustre:
Vitreous
Hardness:
6 - 6½
Specific Gravity:
2.74 - 2.76
Crystal System:
Triclinic
Name:
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 plagioclase (Albite-Anorthite Series).

High- and low-temperature structural modifications exist.

Chemically and stoichiometrically very similar to lawsonite (which contains OH groups and H2O molecules, however).




Unique IdentifiersHide

Mindat ID:
246
Long-form identifier:
mindat:1:1:246:6

IMA Classification of AnorthiteHide

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

Classification of AnorthiteHide

9.FA.35

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H2O
A : Tektosilicates without additional non-tetrahedral anions
16.9.2

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

Mineral SymbolsHide

As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.

SymbolSourceReference
AnIMA–CNMNCWarr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43
AnKretz (1983)Kretz, R. (1983) Symbols of rock-forming minerals. American Mineralogist, 68, 277–279.
AnSiivolam & Schmid (2007)Siivolam, J. and Schmid, R. (2007) Recommendations by the IUGS Subcommission on the Systematics of Metamorphic Rocks: List of mineral abbreviations. Web-version 01.02.07. IUGS Commission on the Systematics in Petrology. download
AnWhitney & Evans (2010)Whitney, D.L. and Evans, B.W. (2010) Abbreviations for names of rock-forming minerals. American Mineralogist, 95, 185–187 doi:10.2138/am.2010.3371
AnThe Canadian Mineralogist (2019)The Canadian Mineralogist (2019) The Canadian Mineralogist list of symbols for rock- and ore-forming minerals (December 30, 2019). download
AnWarr (2020)Warr, L.N. (2020) Recommended abbreviations for the names of clay minerals and associated phases. Clay Minerals, 55, 261–264 doi:10.1180/clm.2020.30

Physical Properties of AnorthiteHide

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

Optical Data of AnorthiteHide

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°
Max. Birefringence:
δ = 0.012 - 0.013
Based on recorded range of RI values above.

Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.

Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.

Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars.

Surface Relief:
Moderate
Dispersion:
r < v weak

Chemistry of AnorthiteHide

Mindat Formula:
Ca(Al2Si2O8)
Element Weights:
Element% weight
O46.007 %
Si20.190 %
Al19.397 %
Ca14.406 %

Calculated from ideal end-member formula.
Common Impurities:
Ti,Fe,Na,K

Chemical AnalysisHide

Oxide wt%:
 1
SO30.01 %
P2O50.02 %
SiO243.72 %
Al2O336.12 %
Fe2O30.06 %
CaO19.11 %
SrO0.22 %
BaO0.02 %
Na2O0.59 %
K2O0.01 %
Total:99.88 %
Empirical formulas:
Sample IDEmpirical Formula
1(Ca0.95Na0.05Sr0.01)[Si2.03Al1.97O8]
Sample references:

Crystallography of AnorthiteHide

Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Cell Parameters:
a = 8.1768 Å, b = 12.8768 Å, c = 14.169 Å
α = 93.17°, β = 115.85°, γ = 92.22°
Ratio:
a:b:c = 0.635 : 1 : 1.1
Unit Cell 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°)

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 www.smorf.nl.

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Crystal StructureHide

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IDSpeciesReferenceLinkYearLocalityPressure (GPa)Temp (K)
0019662AnorthiteWenk H R, Joswig W, Tagai T, Korekawa M, Smith B K (1980) The average structure of An 62-66 labradorite American Mineralogist 65 81-951980Surtsey, Iceland0293
0019663AnorthiteWenk H R, Joswig W, Tagai T, Korekawa M, Smith B K (1980) The average structure of An 62-66 labradorite American Mineralogist 65 81-951980Surtsey, Iceland0293
0019664AnorthiteWenk H R, Joswig W, Tagai T, Korekawa M, Smith B K (1980) The average structure of An 62-66 labradorite American Mineralogist 65 81-951980Lake County, Oregon, USA0293
0019665AnorthiteWenk H R, Joswig W, Tagai T, Korekawa M, Smith B K (1980) The average structure of An 62-66 labradorite American Mineralogist 65 81-951980Lake County, Oregon, USA0293
0019666AnorthiteWenk H R, Joswig W, Tagai T, Korekawa M, Smith B K (1980) The average structure of An 62-66 labradorite American Mineralogist 65 81-951980Gordemo, Verzasca Valley, Switzerland0293
0019667AnorthiteWenk H R, Joswig W, Tagai T, Korekawa M, Smith B K (1980) The average structure of An 62-66 labradorite American Mineralogist 65 81-951980Sissone, Bergell Alps, Switzerland0293
0000370AnorthiteFoit F F, Peacor D R (1973) The anorthite crystal structure at 410 and 830 C American Mineralogist 58 665-67519730683
0000371AnorthiteFoit F F, Peacor D R (1973) The anorthite crystal structure at 410 and 830 C American Mineralogist 58 665-675197301103
0001194AnorthiteAngel R J (1988) High-pressure structure of anorthite American Mineralogist 73 1114-11191988Val Pasmeda, Austria0293
0001195AnorthiteAngel R J (1988) High-pressure structure of anorthite American Mineralogist 73 1114-11191988Val Pasmeda, Austria2.5293
0001196AnorthiteAngel R J (1988) High-pressure structure of anorthite American Mineralogist 73 1114-11191988Val Pasmeda, Austria3.1293
0001286AnorthiteAngel R J, Carpenter M A, Finger L W (1990) Structural variation associated with compositional variation and order-disorder behavior in anorthite-rich feldspars American Mineralogist 75 150-1621990Val Pasmeda, Austria0293
0001287AnorthiteAngel R J, Carpenter M A, Finger L W (1990) Structural variation associated with compositional variation and order-disorder behavior in anorthite-rich feldspars American Mineralogist 75 150-1621990Monte Somma, Italy0293
0001288AnorthiteAngel R J, Carpenter M A, Finger L W (1990) Structural variation associated with compositional variation and order-disorder behavior in anorthite-rich feldspars American Mineralogist 75 150-1621990Monte Somma, Italy0293
0001289AnorthiteAngel R J, Carpenter M A, Finger L W (1990) Structural variation associated with compositional variation and order-disorder behavior in anorthite-rich feldspars sample #115082a American Mineralogist 75 150-1621990South of Blantyre, Nyasalad (Malawi)0293
0020104AnorthiteWadoski-Romeijn E, Armbruster T (2013) Topotactic transformation and dehydration of the zeolite gismondine to a novel Ca feldspar structure American Mineralogist 98 1988-19972013Rio Pian del Foco, Genova province, Italy0623
0006694AnorthiteMatsui T, Kimata M (1997) Crystal chemistry of synthetic Mn-bearing anorthite: Incorporation of MnAl2Si2O8 end-member into feldspar European Journal of Mineralogy 9 333-34419970293
0019668AnorthiteFacchinelli A, Bruno E, Chiari G (1979) The structure of bytownite quenched from 1723 K Acta Crystallographica B35 34-421979satellite dyke, Traversella stock, Sesia Lanzo zone, Western Alps, Italy0293
0019669AnorthiteFacchinelli A, Bruno E, Chiari G (1979) The structure of bytownite quenched from 1723 K Acta Crystallographica B35 34-421979satellite dyke, Traversella stock, Sesia Lanzo zone, Western Alps, Italy0293
0010723AnorthiteWainwright J, Starkey J (1971) A refinement of the structure of anorthite _cod_database_code 1000034 Zeitschrift fur Kristallographie 133 75-8419710293
0020640AnorthiteChiari G, Benna P, Bruno E (1984) The structure of bytownite (An85). A new refinement Zeitschrift fur Kristallographie 169 35-491984Traversella stock, Sesia Lanzo zone, Western Alps, Italy0293
0020641AnorthiteChiari G, Benna P, Bruno E (1984) The structure of bytownite (An85). A new refinement Zeitschrift fur Kristallographie 169 35-491984Traversella stock, Sesia Lanzo zone, Western Alps, Italy0293
0016634AnorthiteKlein S, Korekawa M (1976) Die gemittelte Struktur des Labradorits _cod_database_code 1008757 Neues Jahrbuch fur Mineralogie, Monatshefte 1976 66-6919760293
CIF Raw Data - click here to close

X-Ray Powder DiffractionHide

Loading XRD data...
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:
d-spacingIntensity
3.19 Å(100)
3.18 Å(91)
3.21 Å(63)
3.26 Å(52)
4.04 Å(48)
3.12 Å(39)
3.62 Å(33)
Comments:
Monte Somma, Italy. Pattern is for the low structural modification.

Geological EnvironmentHide

Paragenetic Mode(s):
Paragenetic ModeEarliest Age (Ga)
Stage 1: Primary nebular phases4.567-4.561
3 : Solar nebular condensates (CAIs, AOAs, URIs)>4.565
4 : Primary chondrule phases4.566–4.561
Stage 2: Planetesimal differentiation and alteration4.566-4.550
5 : Primary asteroid phases4.566–4.560
6 : Secondary asteroid phases4.566-4.560
Stage 3a: Earth’s earliest Hadean crust>4.50
8 : Mafic igneous rocks
Near-surface Processes
26 : Hadean detrital minerals
Stage 4b: Highly evolved igneous rocks>3.0
35 : Ultra-alkali and agpaitic igneous rocks
Stage 5: Initiation of plate tectonics<3.5-2.5
40 : Regional metamorphism (greenschist, amphibolite, granulite facies)
Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere<0.6
51 : Pyrometamorphic minerals (see also #54 and #56)<0.36
Geological Setting:
Mafic plutonic rocks

Type Occurrence of AnorthiteHide

Place of Conservation of Type Material:
Museum für Naturkunde, Humboldt Universität, Berlin, Germany, numbers 1999-0087, 1999-0088 (type?).

Synonyms of AnorthiteHide

Other Language Names for AnorthiteHide

Varieties of AnorthiteHide

Barium-Anorthite (of Nockolds and Zies)A Ba-bearing 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.

May show labradorescence (compare labradorite).

The original material, a greenish-white substance, was found in a boulder near Bytown (now Ottawa), and later...
LabradoriteA plagioclase feldspar with an albite : anorthite molar ratio ranging from 30 : 70 to 50 : 50.
An intermediate member of the Albite-Anorthite Series.

Labradorite can display an iridescent optical effect (or schiller) known as labradorescence.
The cause ...
LindsayiteAn altered anorthite.
Lynx EyeVariety of labradorite with green iridescence.
Oregon SunstoneSunstone with inclusions of copper instead of hematite.
Crystallographically oriented nanocrystals of protoenstatite and clinoenstatite in association with copper nanocrystals are responsible for the unusual green and “watermelon” coloration of the or...
SpectroliteA variety of labradorite (strictly, anorthite) showing strong labradorescence due to very fine exsolution of K-feldspar.

Relationship of Anorthite to other SpeciesHide

Other Members of Plagioclase:
AlbiteNa(AlSi3O8)Tric. 1

Common AssociatesHide

Associated Minerals Based on Photo Data:
20 photos of Anorthite associated with HessoniteCa3Al2(SiO4)3
20 photos of Anorthite associated with Clinozoisite(CaCa)(AlAlAl)O[Si2O7][SiO4](OH)
15 photos of Anorthite associated with VesuvianiteCa19Fe3+Al4(Al6Mg2)(◻4)◻[Si2O7]4[(SiO4)10]O(OH)9
15 photos of Anorthite associated with PyrrhotiteFe1-xS
15 photos of Anorthite associated with AlbiteNa(AlSi3O8)
14 photos of Anorthite associated with QuartzSiO2
13 photos of Anorthite associated with Epidote(CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH)
13 photos of Anorthite associated with HedenbergiteCaFe2+Si2O6
12 photos of Anorthite associated with TitaniteCaTi(SiO4)O
11 photos of Anorthite associated with RubyAl2O3

Related Minerals - Strunz-mindat GroupingHide

9.FA.HexacelsianBaAl2Si2O8Hex. 6/mmm (6/m 2/m 2/m) : P63/mcm
9.FA.Wodegongjieite KCa3(Al7Si9)O32Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc
9.FA.05Panunzite(K,Na)AlSiO4Hex. 6 : P63
9.FA.05Yoshiokaite(Ca,Na)[Al(Al,Si)O4]Trig. 3 : P3
9.FA.05NephelineNa3K(Al4Si4O16)Hex. 6 : P63
9.FA.05TrinephelineNaAlSiO4 Hex. 6 : P61
9.FA.05Davidsmithite(Ca,◻)2Na6Al8Si8O32Hex. 6 : P63
9.FA.05KaliophiliteKAlSiO4Trig. 3 : P3
9.FA.05KalsiliteKAlSiO4Hex. 6 2 2 : P63 2 2
9.FA.05CarnegieiteNaAlSiO4Tric.
9.FA.05MegakalsiliteKAlSiO4Hex. 6 : P63
9.FA.05TrikalsiliteK2NaAl3(SiO4)3Hex. 6 : P63
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.30FerrisanidineK[Fe3+Si3O8]Mon. 2/m : B2/m
9.FA.30Buddingtonite(NH4)(AlSi3O8)Mon. 2 : P21
9.FA.30RubiclineRb(AlSi3O8)Mon. 2/m : B2/m
9.FA.30MonalbiteNaAlSi3O8Mon. 2/m : B2/m
9.FA.30MicroclineK(AlSi3O8)Tric. 1
9.FA.30 vaGermanate-celsianBaAl2Ge2O8
9.FA.30CelsianBa(Al2Si2O8)Mon. 2/m
9.FA.30SanidineK(AlSi3O8)Mon. 2/m : B2/m
9.FA.30OrthoclaseK(AlSi3O8)Mon. 2/m : B2/m
9.FA.35ReedmergneriteNaBSi3O8Tric. 1 : P1
9.FA.35AlbiteNa(AlSi3O8)Tric. 1
9.FA.40ParacelsianBa(Al2Si2O8)Mon. 2/m : P21/b
9.FA.45SvyatoslaviteCa(Al2Si2O8)Mon. 2 : P21
9.FA.45KumdykoliteNa(AlSi3O8)Orth. mmm (2/m 2/m 2/m) : Pnnm
9.FA.50SlawsoniteSr(Al2Si2O8)Mon. 2/m : P21/b
9.FA.55LisetiteCaNa2Al4Si4O16Orth. mm2
9.FA.60StronalsiteNa2SrAl4Si4O16Orth.
9.FA.60BanalsiteNa2BaAl4Si4O16Orth. mm2 : Iba2
9.FA.65MaleeviteBaB2Si2O8Orth. mmm (2/m 2/m 2/m) : Pnma
9.FA.65PekoviteSrB2Si2O8Orth. mmm (2/m 2/m 2/m) : Pnma
9.FA.65DanburiteCaB2Si2O8Orth. mmm (2/m 2/m 2/m)
9.FA.70LiebermanniteKAlSi3O8Tet. 4/m : I4/m
9.FA.70Lingunite(Na,Ca)AlSi3O8Tet. 4/m : I4/m
9.FA.70StöffleriteCaAl2Si2O8Tet. 4/m : I4/m
9.FA.75Pfaffenbergite KNa3(Al4Si12)O32Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc
9.FA.75KokchetaviteK(AlSi3O8)Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc

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

Internet Links for AnorthiteHide

References for AnorthiteHide

Reference List:

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.

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