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Microcline

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Formula:
KAlSi
 
3
O
 
8
System:TriclinicColour:White, grey, greyish ...
Lustre:VitreousHardness:6 - 6½
Member of:Feldspar Group
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:Orthoclase


Feldspar Group.

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Classification of Microcline

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:8/J.06-30
Nickel-Strunz 10th (pending) edition ID:9.FA.30

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H2O
A : Tektosilicates without additional non-tetrahedral anions
Dana 8th edition ID:76.1.1.5

76 : TECTOSILICATES Al-Si Framework
1 : Al-Si Framework with Al-Si frameworks
Hey's CIM Ref.:16.3.5

16 : Silicates Containing Aluminum and other Metals
3 : Aluminosilicates of K
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Type Occurrence of Microcline

Co-type Localities:Arendal, Aust-Agder, Norway
Stavern (Fredriksvärn), Larvik, Vestfold, Norway
Year of Discovery:1830

Occurrences of Microcline

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

Physical Properties of Microcline

Lustre: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 (measured):2.54 - 2.57 g/cm3
Density (calculated):2.56 g/cm3

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
Unit Cell Volume:V 720.16 ų (Calculated from Unit Cell)
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).
Crystal Atlas:
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Microcline - Manebach twin

About Crystal Atlas

The mindat.org Crystal Atlas allows you to view a selection of crystal drawings of real and idealised crystal forms for this mineral and, in certain cases, 3d rotating crystal objects. The 3d models and HTML5 code are kindly provided by www.smorf.nl.

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X-Ray Powder Diffraction:
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Radiation - Copper Kα
Data Set:
Horizontal Axis: ° to ° Vertical Axis: % Source Data: Filtered Data:
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°
Maximum Birefringence:δ = 0.007 - 0.010

Chart 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:
KAlSi
 
3
O
 
8
Simplified for copy/paste:KAlSi3O8
Essential elements:Al, K, O, Si
All elements listed in formula:Al, K, O, Si
Common Impurities:Fe,Ca,Na,Li,Cs,Rb,H2O,Pb

Relationship of Microcline to other Species

Member of:Feldspar Group
Other Members of Group:

- +
Albite
NaAlSi
 
3
O
 
8
Amazonite
Andesine
(Na,Ca)[Al(Si,Al)Si
 
2
O
 
8
]
Anorthite
CaAl
 
2
Si
 
2
O
 
8
Anorthoclase
(Na,K)AlSi
 
3
O
 
8
Banalsite
BaNa
 
2
[Al
 
2
Si
 
2
O
 
8
]
 
2
Buddingtonite
(NH
 
4
)AlSi
 
3
O
 
8
Bytownite
(Ca,Na)[Al(Al,Si)Si
 
2
O
 
8
]
Celsian
BaAl
 
2
Si
 
2
O
 
8
Dmisteinbergite
CaAl
 
2
Si
 
2
O
 
8
Hyalophane
(K,Ba)[Al(Si,Al)Si
 
2
O
 
8
]
Labradorite
(Ca,Na)[Al(Al,Si)Si
 
2
O
 
8
]
Oligoclase
(Na,Ca)[Al(Si,Al)Si
 
2
O
 
8
]
Orthoclase
KAlSi
 
3
O
 
8
Paracelsian
BaAl
 
2
Si
 
2
O
 
8
Reedmergnerite
Na[BSi
 
3
O
 
8
]
Sanidine
KAlSi
 
3
O
 
8
Slawsonite
(Sr,Ca)Al
 
2
Si
 
2
O
 
8
Stronalsite
SrNa
 
2
[Al
 
2
Si
 
2
O
 
8
]
 
2
Svyatoslavite
CaAl
 
2
Si
 
2
O
 
8
Common Associates:
QuartzMuscoviteHornblendeBiotite
Related Minerals - Nickel-Strunz Grouping):

- +
9.FA.05Kaliophilite
KAlSiO
 
4
9.FA.05Kalsilite
KAlSiO
 
4
9.FA.05Nepheline
(Na,K)AlSiO
 
4
9.FA.05Panunzite
(K,Na)AlSiO
 
4
9.FA.05Trikalsilite
(K,Na)AlSiO
 
4
9.FA.05Yoshiokaite
(Ca,Na)[Al(Al,Si)O
 
4
]
9.FA.05Megakalsilite
KAlSiO
 
4
9.FA.10Malinkoite
NaBSiO
 
4
9.FA.15Virgilite
LiAlSi
 
2
O
 
6
9.FA.25Lisitsynite
KBSi
 
2
O
 
6
9.FA.30Adularia
KAlSi
 
3
O
 
8
9.FA.30Anorthoclase
(Na,K)AlSi
 
3
O
 
8
9.FA.30Buddingtonite
(NH
 
4
)AlSi
 
3
O
 
8
9.FA.30Celsian
BaAl
 
2
Si
 
2
O
 
8
9.FA.30Hyalophane
(K,Ba)[Al(Si,Al)Si
 
2
O
 
8
]
9.FA.30Orthoclase
KAlSi
 
3
O
 
8
9.FA.30Sanidine
KAlSi
 
3
O
 
8
9.FA.30Rubicline
(Rb,K)AlSi
 
3
O
 
8
9.FA.30Monalbite
NaAlSi
 
3
O
 
8
9.FA.35Albite
NaAlSi
 
3
O
 
8
9.FA.35Andesine
(Na,Ca)[Al(Si,Al)Si
 
2
O
 
8
]
9.FA.35Anorthite
CaAl
 
2
Si
 
2
O
 
8
9.FA.35Bytownite
(Ca,Na)[Al(Al,Si)Si
 
2
O
 
8
]
9.FA.35Labradorite
(Ca,Na)[Al(Al,Si)Si
 
2
O
 
8
]
9.FA.35Oligoclase
(Na,Ca)[Al(Si,Al)Si
 
2
O
 
8
]
9.FA.35Reedmergnerite
Na[BSi
 
3
O
 
8
]
9.FA.40Paracelsian
BaAl
 
2
Si
 
2
O
 
8
9.FA.45Svyatoslavite
CaAl
 
2
Si
 
2
O
 
8
9.FA.45Kumdykolite
NaAlSi
 
3
O
 
8
9.FA.50Slawsonite
(Sr,Ca)Al
 
2
Si
 
2
O
 
8
9.FA.55Lisetite
CaNa
 
2
Al
 
4
Si
 
4
O
 
16
9.FA.60Banalsite
BaNa
 
2
[Al
 
2
Si
 
2
O
 
8
]
 
2
9.FA.60Stronalsite
SrNa
 
2
[Al
 
2
Si
 
2
O
 
8
]
 
2
9.FA.65Danburite
CaB
 
2
Si
 
2
O
 
8
9.FA.65Maleevite
BaB
 
2
Si
 
2
O
 
8
9.FA.65Pekovite
SrB
 
2
Si
 
2
O
 
8
9.FA.70Lingunite
(Na,Ca)AlSi
 
3
O
 
8
9.FA.75Kokchetavite
KAlSi
 
3
O
 
8
Related Minerals - Hey's Index Grouping:

- +
16.3.1Lithosite
K
 
6
Al
 
4
Si
 
8
O
 
25
· 2H
 
2
O
16.3.2Kaliophilite
KAlSiO
 
4
16.3.3Kalsilite
KAlSiO
 
4
16.3.4Leucite
K(AlSi
 
2
O
 
6
)
16.3.6Orthoclase
KAlSi
 
3
O
 
8
16.3.7Sanidine
KAlSi
 
3
O
 
8
16.3.8Muscovite
KAl
 
2
(AlSi
 
3
O
 
10
)(OH)
 
2

Other Names for Microcline

Synonyms:
Microline
Other Languages:
Dutch:Microklien
Finnish:Mikrokliini
French:Microcline
German:Mikrokliner Felsit
Hebrew:מיקרוקלין
Italian:Microclino
Japanese:微斜長石
Lithuanian:Mikroklinas
Polish:Mikroklin
Portuguese:Microclina
Russian:Микроклин
Simplified Chinese:微斜长石
Swedish:Mikroklin
Traditional Chinese:微斜長石
Ukrainian:Мікроклін
Varieties:
AmazoniteChesterliteFerruginous Microcline

Other Information

Health Warning: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

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    Localities for Microcline

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