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Microcline

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Papachacra Mts, Belen Department, Catamarca, Argentina
© Joseph A. Freilich

Show Microcline Photos (302)
Formula:
K[AlSi
 
3
O
 
8
]
System:TriclinicColour:White, grey, greyish ...
Lustre:VitreousHardness:6 - 6½
Name:From the greek mikron (little) and klinein (to stoop).
Dimorph of:Orthoclase


Feldspar Group.

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

Type Locality: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

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Radiation - Copper Kα
Data Set:
Horizontal Axis: ° to ° Vertical Axis: % Source Data: Filtered Data: Peaks:
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:
K[AlSi
 
3
O
 
8
]
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 Group:
Feldspar Group:
Common Associates:
QuartzMuscoviteHornblendeBiotite
Related Minerals - Nickel-Strunz Grouping):

- +
9.FA.05Kaliophilite
K[AlSiO
 
4
]
9.FA.05Kalsilite
K[AlSiO
 
4
]
9.FA.05Nepheline
(Na,K)[AlSiO
 
4
]
9.FA.05Panunzite
(Na,K)[AlSiO
 
4
]
9.FA.05Trikalsilite
(Na,K)[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
Ba[Al
 
2
Si
 
2
O
 
8
]
9.FA.30Hyalophane
(K,Ba)[Al(Si,Al)Si
 
2
O
 
8
]
9.FA.30Orthoclase
K[AlSi
 
3
O
 
8
]
9.FA.30Sanidine
K[AlSi
 
3
O
 
8
]
9.FA.30Rubicline
(Rb,K)[AlSi
 
3
O
 
8
]
9.FA.30Monalbite
Na[AlSi
 
3
O
 
8
]
9.FA.35Albite
Na[AlSi
 
3
O
 
8
]
9.FA.35Andesine
(Na,Ca)[Al(Si,Al)Si
 
2
O
 
8
]
9.FA.35Anorthite
Ca[Al
 
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
Ba[Al
 
2
Si
 
2
O
 
8
]
9.FA.45Svyatoslavite
Ca[Al
 
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
K[AlSiO
 
4
]
16.3.3Kalsilite
K[AlSiO
 
4
]
16.3.4Leucite
KAlSi
 
2
O
 
6
16.3.6Orthoclase
K[AlSi
 
3
O
 
8
]
16.3.7Sanidine
K[AlSi
 
3
O
 
8
]
16.3.8Muscovite
KAl
 
2
[(OH)
 
2
|AlSi
 
3
O
 
10
]

Other Names for Microcline

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

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