Anorthite Mineral Data
General Anorthite Information
Chemical Formula:
CaAl2Si2O8
Composition:
Molecular Weight = 277.41 gm
Sodium 0.41 % Na 0.56 % Na2 O
Calcium 13.72 % Ca 19.20 % CaO
Aluminum 18.97 % Al 35.84 % Al2 O3
Silicon 20.75 % Si 44.40 % SiO2
Oxygen 46.14 % O
______ ______
100.00 % 100.00 % = TOTAL OXIDE
Empirical Formula:
Na0.05 Ca0.95 Al1.95 Si2.05 O8
Environment:
Magmatic and metamorphic rocks.
IMA Status:
Valid Species (Pre-IMA) 1823
Locality:
Monte Somma and Valle di Fassa, Italy. Link to MinDat.org Location Data.
Name Origin:
From the Greek, an + orthos, "not upright" in allusion to the oblique crystals.
Name Pronunciation:
Anorthite + Pronunciation
Synonym:
Ab0
An100
ICSD 654
Indianite
PDF 41-1486
Anorthite Image
Images:
Anorthite Crystallography
Axial Ratios:
a:b:c =0.635:1:1.1003
Cell Dimensions:
a = 8.177, b = 12.877, c = 14.169, Z = 8; alpha = 93.166°, beta = 115.85°, gamma = 91.216° V = 1,340.29 Den(Calc)= 2.75
Crystal System:
Triclinic - Pinacoidal H-M Symbol ( 1 ) Space Group: P1 ,I1
X Ray Diffraction:
By Intensity(I/Io ): 3.2(1), 3.18(0.75), 4.04(0.6),
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Physical Properties of Anorthite
Cleavage:
{001} Perfect, {010} Good
Color:
Colorless, Gray, White, Red, Reddish gray.
Density:
2.72 - 2.75, Average = 2.73
Diaphaneity:
Transparent to Subtransparent to translucent
Fracture:
Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.
Habit:
Euhedral Crystals - Occurs as well-formed crystals showing good external form.
Habit:
Granular - Generally occurs as anhedral to subhedral crystals in matrix.
Habit:
Striated - Parallel lines on crystal surface or cleavage face.
Hardness:
6 - Orthoclase
Luminescence:
Non-fluorescent.
Luster:
Vitreous (Glassy)
Streak:
white
Optical Properties of Anorthite
Gladstone-Dale:
CI meas = -0.02 (Excellent) - where the CI = (1-KPDmeas /KC ) CI calc = -0.015 (Superior) - where the CI = (1-KPDcalc /KC )
KPDcalc = 0.211,KPDmeas = 0.2121,KC = 0.2079 Ncalc = 1.57
Optical Data:
Biaxial (-), a=1.572-1.576, b=1.5785-1.5832, g=1.583-1.588, bire=0.0110-0.0120, 2V(Calc)=78, 2V(Meas)=78. Dispersion relatively weak.
Pleochroism (x):
colorless.
Pleochroism (y):
colorless.
Calculated Properties of Anorthite
Electron Density:
Bulk Density (Electron Density)=2.73 gm/cc note: Specific Gravity of Anorthite =2.75 gm/cc.
Fermion Index:
Fermion Index = 0.01 Boson Index = 0.99
Photoelectric:
PEAnorthite = 3.05 barns/electronU=PEAnorthite x r Electron Density= 8.32 barns/cc.
Radioactivity:
GRapi = 0 (Gamma Ray American Petroleum Institute Units) Anorthite is Not Radioactive
Anorthite Classification
Dana Class:
76.01.03.06 (76) Tectosilicate Al-Si Framework
(76.01) with Al-Si frameworks
(76.01.03) Plagioclase series
76.01.03.00 Plagioclase * (Na,Ca)(Si,Al)4O8 C1 1
76.01.03.01 Albite NaAlSi3O8 C1 1
76.01.03.02 Oligoclase (Na,Ca)(Si,Al)4O8 C1 1
76.01.03.03 Andesine * (Na,Ca)(Si,Al)4O8 C1 1
76.01.03.04 Labradorite * (Ca,Na)(Si,Al)4O8 C1 1
76.01.03.05 Bytownite * (Ca,Na)(Si,Al)4O8 C1 1
76.01.03.06 Anorthite CaAl2Si2O8 P1 ,I1 1
Strunz Class:
09.FA.35 09 - SILICATES (Germanates)
09.F - Tektosilicates without Zeolitic H2O
09.FA -Tektosilicates without additional non-tetrahedral anions, (Al,B):Si = 1:1
09.FA.35 Albite NaAlSi3O8 C1 1
09.FA.35 Bytownite * (Ca,Na)(Si,Al)4O8 C1 1
09.FA.35 Anorthite CaAl2Si2O8 P1 ,I1 1
09.FA.35 Andesine * (Na,Ca)(Si,Al)4O8 C1 1
09.FA.35 Labradorite * (Ca,Na)(Si,Al)4O8 C1 1
09.FA.35 Oligoclase (Na,Ca)(Si,Al)4O8 C1 1
09.FA.35 Reedmergnerite NaBSi3O8 C1 1
09.FA.35 Plagioclase * (Na,Ca)(Si,Al)4O8 C1 1
Other Anorthite Information
See Also:
Links to other databases for Anorthite :
1 - Am. Min. Crystal Structure Database
2 - Amethyst Galleries' Mineral Gallery
3 - Athena
4 - EUROmin Project
5 - Ecole des Mines de Paris
6 - Franklin Minerals(Dunn)
7 - Franklin Minerals(Palache)
8 - GeoScienceWorld
9 - Google Images
10 - Google Scholar
11 - Handbook of Mineralogy (MinSocAm)
12 - Handbook of Mineralogy (UofA)
13 - HyperPhysics
14 - MinDAT
15 - Mineral and Gemstone Kingdom
16 - Mineralienatlas (Deutsch)
17 - Online Mineral Museum
18 - QUT Mineral Atlas
19 - Ruff.Info
20 - UCLA - Petrography Thin-Sections
21 - WWW-MINCRYST
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Anorthite
CaAl2Si2O8
Dana No: 76.01.03.06 Strunz No: 09.FA.35
Locality:
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