Oligoclase Mineral Data

Oligoclase Mineral Data +

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General Oligoclase Information

Chemical Formula:

(Na,Ca)(Si,Al)4O8

Composition:

Molecular Weight = 265.42 gm

Sodium 6.93 % Na 9.34 % Na₂O

Calcium 3.02 % Ca 4.23 % CaO

Aluminum 12.20 % Al 23.05 % Al₂O₃

Silicon 29.63 % Si 63.38 % SiO₂

Oxygen 48.22 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Na_0.8Ca_0.2Al_1.2Si_2.8O₈

Environment:

Magmatic and pegmatitic rocks.

IMA Status:

Valid Species (Pre-IMA) 1826

Locality:

Twedestrand, Norway. Link to MinDat.org Location Data.

Name Origin:

From the Greek, oligos and kasein, "little cleavage."

Synonym:

Ab80

An20

Sunstone

Oligoclase Image

Images:

Oligoclase Plagioclase

Comments: Rectangular cleavage fragment of salmon-orange oligoclase (sunstone) feldspar.
Location: Norway. Scale: 47x30x7 mm.
© John Betts - Fine Minerals

Images:

Oligoclase Plagioclase

Comments: Clear glassy crystalline oligoclase with milky quartz and muscovite.
Location: Bakersville, Mitchell County, North Carolina, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Oligoclase Crystallography

Axial Ratios:

a:b:c =0.6377:1:0.6651

Cell Dimensions:

a = 8.15, b = 12.78, c = 8.5, Z = 5; alpha = 94.016°, beta = 116.3333°, gamma = 88.667° V = 791.30 Den(Calc)= 2.78

Crystal System:

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

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

By Intensity(I/I_o): 3.2(1), 3.74(0.8), 4.02(0.8),

Forms:

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Forms: [ 0 0 1] [ 1 0 0] [ 1 0 1] [ 0 1 0]

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Physical Properties of Oligoclase

Cleavage:

[001] Perfect, [010] Good

Color:

Brown, Colorless, Greenish, Gray, Yellowish.

Density:

2.64 - 2.66, Average = 2.65

Diaphaniety:

Transparent 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.

Hardness:

7 - Quartz

Luminescence:

Fluorescent.

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Oligoclase

Gladstone-Dale:

CI meas= 0.007 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.054 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1951,KPDmeas= 0.2047,KC= 0.2062

Optical Data:

Biaxial (+), a=1.533-1.543, b=1.5368-1.5477, g=1.542-1.552, bire=0.0090, 2V(Calc)=82-86, 2V(Meas)=82. Dispersion none.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Pleochroism (z):

colorless.

Calculated Properties of Oligoclase

Electron Density:

r_electron=2.63 gm/cc
note: r_Oligoclase=2.65 gm/cc.

Fermion Index

Fermion Index = 0.0141
Boson Index = 0.9859

Photoelectric:

PE_Oligoclase= 1.98 barns/electron
U=PE_Oligoclase x r_electron= 5.19 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Oligoclase is Not Radioactive

Oligoclase Classification

Dana Class:

76.1.3.2 (76)Tectosilicate Al-Si Framework

(76.1)with Al-Si frameworks

(76.1.3)Plagioclase series

76.1.3.0 Plagioclase* (Na,Ca)(Si,Al)4O8 C1 1

76.1.3.1 Albite NaAlSi3O8 C1 1

76.1.3.2 Oligoclase (Na,Ca)(Si,Al)4O8 C1 1

76.1.3.3 Andesine* (Na,Ca)(Si,Al)4O8 C1 1

76.1.3.4 Labradorite* (Ca,Na)(Si,Al)4O8 C1 1

76.1.3.5 Bytownite* (Ca,Na)(Si,Al)4O8 C1 1

76.1.3.6 Anorthite CaAl2Si2O8 P1,I1 1

Strunz Class:

VIII/J.07-30 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 Oligoclase Information

References:

NAME( Sinkankas66) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

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Oligoclase

(Na,Ca)(Si,Al)4O8
Dana No: 76.1.3.2 Strunz No: VIII/J.07-30
Locality:

Notes: