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Microcline

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

Show Microcline Photos (257)
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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X-Ray Powder Diffraction:
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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

Related to:
  • 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.

    Internet Links for Microcline

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  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Search for Microcline in the Natural History Museum (London) online catalogue
  • Microcline details from Handbook of Mineralogy (PDF)
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    Localities for Microcline

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