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Labradorite

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Formula:
(Ca,Na)[Al(Al,Si)Si2O8]
Colour:
Pale green, blue, ...
Hardness:
6 - 6½
Member of:
Name:
From the occurrence at Ford Harbour, Paul Island,Labrador, Canada (Nain anorthosite).
A variety of Anorthite

A plagioclase feldspar with an albite : anorthite molar ratio ranging from 30 : 70 to 50 : 50.
An intermediate member of the Albite-Anorthite Series.

Originally found at Ford Harbour, Paul Island, near Nain, off the east coast of Labrador, Newfoundland and Labrador [56° 30' N, 61° 30' W].


Visit gemdat.org for gemological information about Labradorite.

Classification of Labradorite

9.FA.35

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H2O
A : Tektosilicates without additional non-tetrahedral anions
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Physical Properties of Labradorite

Sub-Vitreous
Colour:
Pale green, blue, colourless, grey-white
Streak:
White
Hardness (Mohs):
6 - 6½
Cleavage:
Perfect
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Optical Data of Labradorite

Type:
Biaxial (+)
RI values:
nα = 1.554 - 1.563 nβ = 1.559 - 1.568 nγ = 1.562 - 1.573
2V:
Measured: 85° , Calculated: 78° to 86°
Max Birefringence:
δ = 0.008 - 0.010
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Low
Dispersion:
none

Chemical Properties of Labradorite

Formula:
(Ca,Na)[Al(Al,Si)Si2O8]
Essential elements:
All elements listed in formula:

Relationship of Labradorite to other Species

Member of:
Other Members of Group:
AlbiteNaAlSi3O8
Amazonite
Andesine(Na,Ca)[Al(Si,Al)Si2O8]
AnorthiteCaAl2Si2O8
Anorthoclase(Na,K)AlSi3O8
BanalsiteBaNa2[Al2Si2O8]2
Buddingtonite(NH4)AlSi3O8
Bytownite(Ca,Na)[Al(Al,Si)Si2O8]
CelsianBaAl2Si2O8
DmisteinbergiteCaAl2Si2O8
Hyalophane(K,Ba)[Al(Si,Al)Si2O8]
MicroclineKAlSi3O8
Oligoclase(Na,Ca)[Al(Si,Al)Si2O8]
OrthoclaseKAlSi3O8
ParacelsianBaAl2Si2O8
ReedmergneriteNa[BSi3O8]
SanidineKAlSi3O8
Slawsonite(Sr,Ca)Al2Si2O8
StronalsiteSrNa2[Al2Si2O8]2
SvyatoslaviteCaAl2Si2O8
9.FA.05KaliophiliteKAlSiO4
9.FA.05KalsiliteKAlSiO4
9.FA.05Nepheline(Na,K)AlSiO4
9.FA.05Panunzite(K,Na)AlSiO4
9.FA.05Trikalsilite(K,Na)AlSiO4
9.FA.05Yoshiokaite(Ca,Na)[Al(Al,Si)O4]
9.FA.05MegakalsiliteKAlSiO4
9.FA.10MalinkoiteNaBSiO4
9.FA.15VirgiliteLiAlSi2O6
9.FA.25LisitsyniteKBSi2O6
9.FA.30AdulariaKAlSi3O8
9.FA.30Anorthoclase(Na,K)AlSi3O8
9.FA.30Buddingtonite(NH4)AlSi3O8
9.FA.30CelsianBaAl2Si2O8
9.FA.30Hyalophane(K,Ba)[Al(Si,Al)Si2O8]
9.FA.30MicroclineKAlSi3O8
9.FA.30OrthoclaseKAlSi3O8
9.FA.30SanidineKAlSi3O8
9.FA.30Rubicline(Rb,K)AlSi3O8
9.FA.30MonalbiteNaAlSi3O8
9.FA.35AlbiteNaAlSi3O8
9.FA.35Andesine(Na,Ca)[Al(Si,Al)Si2O8]
9.FA.35AnorthiteCaAl2Si2O8
9.FA.35Bytownite(Ca,Na)[Al(Al,Si)Si2O8]
9.FA.35Oligoclase(Na,Ca)[Al(Si,Al)Si2O8]
9.FA.35ReedmergneriteNa[BSi3O8]
9.FA.40ParacelsianBaAl2Si2O8
9.FA.45SvyatoslaviteCaAl2Si2O8
9.FA.45KumdykoliteNaAlSi3O8
9.FA.50Slawsonite(Sr,Ca)Al2Si2O8
9.FA.55LisetiteCaNa2Al4Si4O16
9.FA.60BanalsiteBaNa2[Al2Si2O8]2
9.FA.60StronalsiteSrNa2[Al2Si2O8]2
9.FA.65DanburiteCaB2Si2O8
9.FA.65MaleeviteBaB2Si2O8
9.FA.65PekoviteSrB2Si2O8
9.FA.70Lingunite(Na,Ca)AlSi3O8
9.FA.75KokchetaviteKAlSi3O8

Other Names for Labradorite

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Labradorite

Reference List:
Rose. G. (1823): Über den Feldspat, Albit, Labradorit und Anorthit, Annalen der Physik und Chemie, Vol. 73/NF-43, 175-208.

Acta Crystallographica (1988): B44: 344.

Hans Boysen & Stefan Kek (2015): The modulated structure of labradorite. Zeitschrift für Kristallographie - Crystalline Materials 230, 23–35.

http://rruff.info/doclib/hom/labradorite.pdf

Internet Links for Labradorite

Specimens:
The following Labradorite specimens are currently listed for sale on minfind.com.

Localities for Labradorite

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.
Mineral and/or Locality  
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