Anorthoclase Mineral Data

Anorthoclase Mineral Data +

General Anorthoclase Information

Chemical Formula:

(Na,K)AlSi3O8

Composition:

Molecular Weight = 266.25 gm

Potassium 3.67 % K 4.42 % K₂O

Sodium 6.48 % Na 8.73 % Na₂O

Aluminum 10.13 % Al 19.15 % Al₂O₃

Silicon 31.65 % Si 67.70 % SiO₂

Oxygen 48.07 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Na_0.75K_0.25AlSi₃O₈

Environment:

In high-temperature sodic volcanic and hypabyssal rocks.

IMA Status:

Valid Species (Pre-IMA) 1885

Locality:

Rather abundant worldwide. Some localities for well-characterized material include: on Pantelleria and Ustica Islands, Italy. At Larvik, Norway. From Berkum, North Rhine-Westphalia, Ge Link to MinDat.org Location Data.

Name Origin:

From the Greek for "oblique" and "fracture," descriptive of the cleavage

Synonym:

ICSD 31180

PDF 9-478

Soda Microcline

Anorthoclase Image

Images:

Anorthoclase

Comments: Two white crystals of anorthoclase (possibly mislabeled and actually anorthite.
Location: Kusukidani, Wakayama Prefecture, Kinki Region, Honshu island, Japan. Scale: 15x14x6 mm.
© John Betts - Fine Minerals

Anorthoclase Crystallography

Axial Ratios:

a:b:c =0.6406:1:0.5546

Cell Dimensions:

a = 8.2, b = 12.8, c = 7.1, Z = 4; alpha = 90°, beta = 116°, gamma = 90° V = 669.80 Den(Calc)= 2.64

Crystal System:

Triclinic - PinacoidalH-M Symbol ( 1) Space Group: C1

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 3.211(1), 3.243(0.9), 4.106(0.16),

Crystal Structure:

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Harlow G E , American Mineralogist , 67 (1982) p.975-996, The anorthoclase structures: The effects of temperature and composition, Grande Calderira, Or = 32.5, T = 23 deg C, feldspar

View Additional jPOWD Structure files for Anorthoclase
[1] [2] [3] [4] [5]

Physical Properties of Anorthoclase

Cleavage:

[001] Perfect, [010] Good

Color:

Colorless, Green, Gray, Gray pink, Yellow.

Density:

2.57 - 2.6, Average = 2.58

Diaphaniety:

Transparent

Fracture:

Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.

Habit:

Disseminated - Occurs in small, distinct particles dispersed in matrix.

Habit:

Granular - Generally occurs as anhedral to subhedral crystals in matrix.

Hardness:

6 - Orthoclase

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Anorthoclase

Gladstone-Dale:

CI meas= 0.007 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.027 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2001,KPDmeas= 0.2043,KC= 0.2057

Optical Data:

Biaxial (-), a=1.519-1.529, b=1.524-1.534, g=1.527-1.536, bire=0.0070-0.0080, 2V(Calc)=64-74, 2V(Meas)=34-60. Dispersion r > v.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Pleochroism (z):

colorless.

Calculated Properties of Anorthoclase

Electron Density:

r_electron=2.56 gm/cc
note: r_Anorthoclase=2.59 gm/cc.

Fermion Index

Fermion Index = 0.01501
Boson Index = 0.98499

Photoelectric:

PE_Anorthoclase= 1.98 barns/electron
U=PE_Anorthoclase x r_electron= 5.08 barns/cc.

Radioactivity:

GRapi = 52.50 (Gamma Ray American Petroleum Institute Units)

Estimated Radioactivity from Anorthoclase - barely detectable

Anorthoclase Classification

Dana Class:

76.1.1.6 (76)Tectosilicate Al-Si Framework

(76.1)with Al-Si frameworks

(76.1.1)K (Na,Ba) feldspars

76.1.1.1 Orthoclase KAlSi3O8 C 2/m 2/m

76.1.1.2 Sanidine (K,Na)(Si,Al)4O8 C 2/m 2/m

76.1.1.3 Hyalophane (K,Ba)Al(Si,Al)3O8 C 2/m 2/m

76.1.1.4 Celsian BaAl2Si2O8 I21/c 2/m

76.1.1.5 Microcline KAlSi3O8 C1 1

76.1.1.6 Anorthoclase (Na,K)AlSi3O8 C1 1

76.1.1.7 Rubicline! (Rb,K)AlSi3O8 P1 1

76.1.1.8 Filatovite! K[(Al,Zn)2(As,Si)2O8] I2/c 2/m

Strunz Class:

VIII/J.07-10 VIII - Silicates

VIII/J - Tectosilicates (network) without anions unfamiliar to the tetraheders

VIII/J.07 - Feldspar group, Anorthoclase - Anorthite - Banalcite series

VIII/J.07-10 Anorthoclase (Na,K)AlSi3O8 C1 1

VIII/J.07-20 Albite NaAlSi3O8 C1 1

VIII/J.07-30 Oligoclase (Na,Ca)(Si,Al)4O8 C1 1

VIII/J.07-40 Andesine* (Na,Ca)(Si,Al)4O8 C1 1

VIII/J.07-50 Labradorite* (Ca,Na)(Si,Al)4O8 C1 1

VIII/J.07-60 Bytownite* (Ca,Na)(Si,Al)4O8 C1 1

VIII/J.07-70 Anorthite CaAl2Si2O8 P1,I1 1

VIII/J.07-75 Dmisteinbergite CaAl2Si2O8 P 6/mmm 6/m 2/m 2/m

VIII/J.07-80 Svyatoslavite CaAl2Si2O8 P 2₁ 2

VIII/J.07-90 Stronalsite SrNa2Al4Si4O16 I bam,Iba2 Ortho

VIII/J.07-100 Banalsite BaNa2Al4Si4O16 I bam 2/m 2/m 2/m

VIII/J.07-110 Filatovite! K[(Al,Zn)2(As,Si)2O8] I2/c 2/m

Other Anorthoclase Information

References:

NAME( AntBidBlaNic2) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

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Anorthoclase

(Na,K)AlSi3O8
Dana No: 76.1.1.6 Strunz No: VIII/J.07-10
Locality:

Notes: