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Labradorite

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

Physical Properties of Labradorite

Sub-Vitreous
Colour:
Pale green, blue, colourless, grey-white
Streak:
White
Hardness (Mohs):
6 - 6½
Cleavage:
Perfect

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]
Elements listed in formula:
X-Ray Powder Diffraction:
Image Loading

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

Relationship of Labradorite to other Species

Member of:
Other Members of Group:
AlbiteNa(AlSi3O8)
AmazoniteK(AlSi3O8)
Andesine(Na,Ca)[Al(Si,Al)Si2O8]
AnorthiteCa(Al2Si2O8)
Anorthoclase(Na,K)AlSi3O8
BanalsiteNa2BaAl4Si4O16
Buddingtonite(NH4)(AlSi3)O8
Bytownite(Ca,Na)[Al(Al,Si)Si2O8]
CelsianBa(Al2Si2O8)
DmisteinbergiteCa(Al2Si2O8)
FilatoviteK(Al,Zn)2(As,Si)2O8
HexacelsianBaAl2Si2O8
Hyalophane(K,Ba)[Al(Si,Al)Si2O8]
KokchetaviteK(AlSi3O8)
KumdykoliteNa(AlSi3O8)
MicroclineK(AlSi3O8)
Oligoclase(Na,Ca)[Al(Si,Al)Si2O8]
OrthoclaseK(AlSi3O8)
ParacelsianBa(Al2Si2O8)
ReedmergneriteNaBSi3O8
RubiclineRb(AlSi3O8)
SanidineK(AlSi3O8)
SlawsoniteSr(Al2Si2O8)
StronalsiteNa2SrAl4Si4O16
SunstoneA variety of feldspar (microcline or oligoclase) that has schiller, commonly with an orange/brown background color, ...
SvyatoslaviteCa(Al2Si2O8)
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)(AlSi3)O8
9.FA.30CelsianBa(Al2Si2O8)
9.FA.30Hyalophane(K,Ba)[Al(Si,Al)Si2O8]
9.FA.30MicroclineK(AlSi3O8)
9.FA.30OrthoclaseK(AlSi3O8)
9.FA.30SanidineK(AlSi3O8)
9.FA.30RubiclineRb(AlSi3O8)
9.FA.30MonalbiteNaAlSi3O8
9.FA.35AlbiteNa(AlSi3O8)
9.FA.35Andesine(Na,Ca)[Al(Si,Al)Si2O8]
9.FA.35AnorthiteCa(Al2Si2O8)
9.FA.35Bytownite(Ca,Na)[Al(Al,Si)Si2O8]
9.FA.35Oligoclase(Na,Ca)[Al(Si,Al)Si2O8]
9.FA.35ReedmergneriteNaBSi3O8
9.FA.40ParacelsianBa(Al2Si2O8)
9.FA.45SvyatoslaviteCa(Al2Si2O8)
9.FA.45KumdykoliteNa(AlSi3O8)
9.FA.50SlawsoniteSr(Al2Si2O8)
9.FA.55LisetiteCaNa2Al4Si4O16
9.FA.60BanalsiteNa2BaAl4Si4O16
9.FA.60StronalsiteNa2SrAl4Si4O16
9.FA.65DanburiteCaB2Si2O8
9.FA.65MaleeviteBaB2Si2O8
9.FA.65PekoviteSrB2Si2O8
9.FA.70Lingunite(Na,Ca)AlSi3O8
9.FA.75KokchetaviteK(AlSi3O8)

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.

Labradorite in petrology

An essential component of (items highlighted in red)
Accessory component of (items highlighted in red)

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

Jin, S. & Xu, H. (2017): Study on structure variations of incommensurately modulated labradorite feldspars with different cooling histories. American Mineralogist: 102 (in press); http://forum.amiminerals.it/viewtopic.php?f=5&t=13473 (2017)

Internet Links for Labradorite

mindat.org URL:
https://www.mindat.org/min-2308.html
Please feel free to link to this page.
Specimens:
The following Labradorite specimens are currently listed for sale on minfind.com.

Localities for Labradorite

Mineral and/or Locality  
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