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Microcline

This page kindly sponsored by Norman King
Formula:
KAlSi3O8
System:
Triclinic
Colour:
White, grey, greyish ...
Lustre:
Vitreous
Hardness:
6 - 6½
Member of:
Name:
Named in 1830 by Johann Friedrich August Breithaupt to a reddish to brownish feldspar from Arendal, Norway, and a feldspar with bluish schiller from Stavern (formerly Fredrichsvärn), Norway, from the Greek μικρός (little) and κλινειν (to incline), in allusion to the small departure from monoclinic symmetry.
Dimorph of:

Classification of Microcline

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
9.FA.30

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H2O
A : Tektosilicates without additional non-tetrahedral anions
76.1.1.5

76 : TECTOSILICATES Al-Si Framework
1 : Al-Si Framework with Al-Si frameworks
16.3.5

16 : Silicates Containing Aluminum and other Metals
3 : Aluminosilicates of K
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http://www.mindat.org/min-2704.html
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Type Occurrence of Microcline

Year of Discovery:
1830

Occurrences of Microcline

Geological Setting:
Plutonic felsic rocks, pegmatites, high grade metamorphic veins, hydrothermal veins

Physical Properties of Microcline

Vitreous
Diaphaneity (Transparency):
Transparent, Translucent
Comment:
Pearly on cleavage
Colour:
White, grey, greyish yellow, yellowish, tan, salmon-pink, bluish green, green.
Streak:
White
Hardness (Mohs):
6 - 6½
Tenacity:
Brittle
Cleavage:
Perfect
on [001], good on [010]
Parting:
on {100}{110}{110}{201}
Fracture:
Irregular/Uneven
Density:
2.54 - 2.57 g/cm3 (Measured)    2.56 g/cm3 (Calculated)

Crystallography of Microcline

Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Cell Parameters:
a = 8.5784Å, b = 12.96Å, c = 7.2112Å
α = 90.3°, β = 116.05°, γ = 89°
Ratio:
a:b:c = 0.662 : 1 : 0.556
Z:
4
Morphology:
Prismatic crystals (to 50 m and 13,500 t), granular, massive. Commonly forms perthitic intergrowths.
Twinning:
Carlsbad, Baveno, Manebach, polysynthetic on albite and pericline laws.
Comment:
Non-standard unit-cell setting (space group C-1, chosen by convention to facilitate comparison with C-centred monoclinic orthoclase and sanidine); reduced cell has the following cell-parameters: ~7.22, ~7.62, ~7.92 Å, ~113.1, ~104.2, ~103.7° (space group P-1).

Crystallographic forms of Microcline

Crystal Atlas:
Image Loading
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Microcline - Manebach twin
3d models and HTML5 code kindly provided by www.smorf.nl.

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Edge Lines | Miller Indicies | Axes

Transparency
Opaque | Translucent | Transparent

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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 Microcline

Type:
Biaxial (-)
RI values:
nα = 1.514 - 1.529 nβ = 1.518 - 1.533 nγ = 1.521 - 1.539
2V:
Measured: 66° to 103°, Calculated: 80°
Max Birefringence:
δ = 0.007 - 0.010
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Low
Dispersion:
r > v weak

Chemical Properties of Microcline

Formula:
KAlSi3O8
Essential elements:
All elements listed in formula:
Common Impurities:
Fe,Ca,Na,Li,Cs,Rb,H2O,Pb

Relationship of Microcline 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]
Labradorite(Ca,Na)[Al(Al,Si)Si2O8]
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.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.35Labradorite(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
16.3.1LithositeK6Al4Si8O25 · 2H2O
16.3.2KaliophiliteKAlSiO4
16.3.3KalsiliteKAlSiO4
16.3.4LeuciteK(AlSi2O6)
16.3.6OrthoclaseKAlSi3O8
16.3.7SanidineKAlSi3O8
16.3.8MuscoviteKAl2(AlSi3O10)(OH)2

Other Names for Microcline

Name in Other Languages:
Finnish:Mikrokliini
French:Microcline
Italian:Microclino
Japanese:微斜長石
Lithuanian:Mikroklinas
Polish:Mikroklin
Portuguese:Microclina
Simplified Chinese:微斜长石
Swedish:Mikroklin
Traditional Chinese:微斜長石

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.
Industrial Uses:
Ceramics

References for Microcline

Reference List:
Breithaupt, A. (1830): Ueber die Felsite und einige neue Specien ihres Geschlechts. Journal für Chemie und Physik, 60: 316-330

Bachinski, S.W. and Müller, G. (1971) Experimental determinations of the microcline-low albite solvus. Journal of Petrology: 12: 329-356.

Eggleton, R.A. and Buseck, P.R. (1980) The orthoclase-microcline inversion: A high resolution transmission electron microscope study and strain analysis. Contributions to Mineralogy and Petrology: 74: 123-133.

Fitz Gerald, J.D. and McLaren, A.C. (1982) The microstructures of microcline from some granitic rocks and pegmatites. Contributions to Mineralogy and Petrology: 80: 219-229.

Bulletin de la Société française de Minéralogie et de Cristallographie (1984): 107: 401.

Goldsmith, J. (1988) Enhanced Al/Si diffusion in KAlSi3O8 at high pressures: the effect of hydrogen. Journal of Geology: 96: 109-124.

Canadian Mineralogist (1990): 28: 771.

Waldron, K.A., Parsons, I., and Brown, W.L. (1993) Solution-redeposition and the orthoclase-microcline transformation: evidence from granulites and relevance to 18O exchange. Mineralogical Magazine: 57: 687-695.

Allan, D.R. & R.J. Angel (1997): A high-pressure structural study of microcline (KAlSi3O8) to 7 GPa: European Journal of Mineralogy: 9: 263-275.

Internet Links for Microcline

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

Localities for Microcline

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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