Labradorite Mineral Data

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General Labradorite Information

Chemical Formula:

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

Composition:

Molecular Weight = 271.81 gm

Sodium 3.38 % Na 4.56 % Na₂O

Calcium 8.85 % Ca 12.38 % CaO

Aluminum 15.88 % Al 30.01 % Al₂O₃

Silicon 24.80 % Si 53.05 % SiO₂

Oxygen 47.09 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Na_0.4Ca_0.6Al_1.6Si_2.4O₈

Environment:

Magmatic and metamorphic rocks.

IMA Status:

Not Approved IMA 1780

Locality:

Labrador peninsula, Canada. Link to MinDat.org Location Data.

Name Origin:

Named after its locality.

Name Pronunciation:

Labradorite + Pronunciation

Synonym:

Ab40

An60

Spectrolite

Labradorite Image

Images:

Labradorite Plagioclase

Comments: Dual view of a cleavage fragment of labradorite showing the multi-colored labradorescence (schiller effect) and the same area viewed without the color. The color is due to optical interference on Bøggild exsolution lamellae.
Location: Ihosy, Betroka district, Toliara Province, Madagascar. Scale: Picture size 3x3 cm.
© Dave Barthelmy

Labradorite Crystallography

Axial Ratios:

a:b:c =0.6351:1:0.7912

Cell Dimensions:

a = 8.155, b = 12.84, c = 10.16, Z = 6; alpha = 93.5°, beta = 116.25°, gamma = 89.133° V = 952.25 Den(Calc)= 2.84

Crystal System:

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

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

By Intensity(I/I_o): 3.18(1), 3.21(0.7), 3.76(0.7),

Forms:

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Forms: ( 0 0 1) ( 1 0 0) ( 1 0 1) ( 0 1 0)

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Crystal Structure:

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Wenk H R , Joswig W , Tagai T , Korekawa M , Smith B K , American Mineralogist , 65 (1980) p.81-95, The average structure of An 62-66 labradorite, Surtsey x-ray, feldspar

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

Physical Properties of Labradorite

Cleavage:

{001} Perfect, {010} Good, {110} Distinct

Color:

Colorless, Gray, Gray white, White, Light green.

Density:

2.68 - 2.71, Average = 2.69

Diaphaneity:

Translucent to transparent

Fracture:

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

Habit:

Crystalline - Coarse - Occurs as well-formed coarse sized crystals.

Habit:

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

Habit:

Striated - Parallel lines on crystal surface or cleavage face.

Hardness:

7 - Quartz

Luminescence:

Non-fluorescent.

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Labradorite

Gladstone-Dale:

CI meas= -0.009 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.043 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1983,KPDmeas= 0.2089,KC= 0.2071
Ncalc = 1.56 - 1.59

Optical Data:

Biaxial (+), a=1.554-1.563, b=1.5588-1.5675, g=1.562-1.573, bire=0.0080-0.0100, 2V(Calc)=78-86, 2V(Meas)=85.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Calculated Properties of Labradorite

Electron Density:

Bulk Density (Electron Density)=2.67 gm/cc
note: Specific Gravity of Labradorite =2.70 gm/cc.

Fermion Index:

Fermion Index = 0.01
Boson Index = 0.99

Photoelectric:

PE_Labradorite= 2.56 barns/electron
U=PE_Labradorite x rElectron Density= 6.84 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Labradorite is Not Radioactive

Labradorite Classification

Dana Class:

76.01.03.04 (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 Labradorite Information

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Print or Cut-and-Paste your Labradorite Specimen Label here :

Labradorite

(Ca,Na)(Si,Al)4O8
Dana No: 76.01.03.04 Strunz No: 09.FA.35
Locality:

Notes: