Muscovite

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Muscovite
Muscovite-70800.jpg
Star-shaped twinned muscovite crystals from Minas Gerais , Brazil (size 5.9 cm × 5.1 cm × 3.6 cm)
General and classification
other names
  • Antonite
  • Women glass
  • Potash mica
  • Cat silver
  • Muscovite
  • Alumina mica
chemical formula KAl 2 [(OH, F) 2 | AlSi 3 O 10 ]
Mineral class
(and possibly department) 		Layered silicates (phyllosilicates) - mica group - celadonite-muscovite series
System no. to Strunz
and to Dana 		9.EC.15 ( 8th edition : VIII / H.10)
71.02.02a.01
Similar minerals Lepidolite , paragonite , talc
Crystallographic Data
Crystal system monoclinic or trigonal
Crystal class ; symbol see modifications
Space group see crystal structure
Frequent crystal faces {001}, {110}, more rarely {010} and {111}
Twinning Twin axis [310], twin plane (001) and formation of 6-pointed stars; Oriented adhesions with biotite and other mica
Physical Properties
Mohs hardness 2.5 parallel [001]; parallel [001]
Density (g / cm 3 ) measured: 2.77 to 2.88; calculated: 2.83
Cleavage very perfect after {001}
Break ; Tenacity uneven
colour colorless, yellowish, brownish, rarely reddish, greenish
Line color White
transparency transparent to translucent
shine Glass gloss, mother-of-pearl, matt
radioactivity hardly measurable
Crystal optics
Refractive indices n α  = 1.552 to 1.576
n β  = 1.582 to 1.615
n γ  = 1.587 to 1.618
Birefringence δ = 0.035 to 0.042
Optical character biaxial negative
Axis angle 2V =
2v x = 30 ° to 47 °
Pleochroism weak, colorless or bluish-greenish-yellow-bluish-green
Other properties
Chemical behavior Not soluble in HCl or H 2 SO 4
Special features rare pleochroic halos around zirconium inclusions

Muscovite (also muscovite , clay mica , cats silver , Antonit , Mrs. Glass , potassium mica ) is a very common mineral from the mica group within the mineral class of " silicates and Germanates ". Depending on the modification, it crystallizes in the monoclinic or trigonal crystal system with the general chemical composition KAl 2 [(OH, F) 2 | AlSi 3 O 10 ]. Structurally, it belongs to the layered silicates .

Muscovite usually develops tabular, leafy, scaly crystals , but also massive aggregates in yellowish, brownish, reddish or greenish color. Colorless crystals are also known. More rarely, but in meter-sized crystals, muscovite also occurs pseudo-hexagonally, i.e. the crystal form shows an apparently hexagonal symmetry through twinning .

Its cleavage is very perfect and the split sheets are elastically flexible. This property, which it has in common with dark mica ( biotite ), can give rocks a slatey structure.

Etymology and history

Muscovite means something like Moscow glass in Russian and was so named by James Dwight Dana in 1850 because it occurs in Russia in large, coarse-leaved aggregates and was previously used for glazing windows and images of saints. Due to its heat resistance, it is also very suitable as a protective glass for furnace windows .

classification

In the 8th edition of the mineral systematics according to Strunz , which is now outdated, but still in use , muscovite belonged to the division of "phyllosilicates", where together with celadonite the "celadonite-muscovite series (Phengite)" with the system no. VIII / H.10 and the other members aluminoseladonite , boromuscovite , chromophyllite , chromium seladonite , ferro-aluminoseladonite , ferroseladonite , ganterite , nanpingite , paragonite , roscoelite and tobelite .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies muscovite in the category of "phyllosilicates". This is, however, further subdivided according to the crystal structure, so that the mineral, according to its structure, can be found in the sub-section "Layered silicates (phyllosilicates) with mica tablets, composed of tetrahedral or octahedral networks", where the sole namesake is the "Muscovite group" with the system No. 9.EC.15 and the other members aluminoseladonite, boromuscovite, celadonite, chernykhite, chrome seladonite, chrome phyllite, ferro-aluminoseladonite, ferro-aluminoseladonite, ferroseladonite, ganterite, montdorite, nanpingite, paragonite, roscoelite, tainiolite and tobelite.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , also classifies muscovite into the “layered silicate minerals” section. Here he is a member and namesake of the " mica group (muscovite subgroup) " with the system no. 71.02.02a can be found in the subsection “ Layered Silicates: Layers of six-membered rings with 2: 1 layers”.

Crystal structure

Muscovite crystallizes polytype in monoclinic symmetry , which are designated as muscovite-1M , muscovite-2M 1 and muscovite-2M 2 , as well as in trigonal symmetry with the designation muscovite-3T and in triclinic symmetry with the designation muscovite-2A .

Crystallographic Data
Polytype Crystal system Space group Lattice parameters and formula units per unit cell (Z)
Muscovite 1M monoclinic C 2 / m (No. 12)Template: room group / 12 a  = 5.21  Å ; b  = 8.99 Å; c  = 10.27 Å and β = 101.6 ° and Z = 2
Muscovite-2M 1 C 2 / c (No. 15)Template: room group / 15 a  = 5.20  Å ; b  = 9.03 Å; c  = 20.11 Å and β = 95.8 ° and Z = 4
Muscovite-2M 2 C 2 / c (No. 15)Template: room group / 15 a  = 8.96  Å ; b  = 5.17 Å; c  = 20.31 Å and β = 100.7 ° and Z = 4
Muscovite 3T trigonal P 3 1 12 (No. 151) or P 3 1 21 (No. 152)Template: room group / 151Template: room group / 152 a  = 5.21  Å and c  = 29.8 Å and Z = 3
Muscovite 2A triclinic C 1 (No. 2, position 3)Template: room group / 2.3 a  = 5.19  Å ; b  = 9.01 Å; c  = 20.04 Å; α = 90.0 °; β = 95.7 ° and γ = 90.0 ° and Z = 4

Modifications and varieties

Muscovite is a collective name for the modifications :

  • Muscovite 2M 1 - monoclinic prismatic - 2 / m (C 2h )
  • Muscovite-1M , also muscovite-2Md - monoclinic
  • Muscovite 3T - trigonal
Red alurgite
Fuchsite variety with glaucophane

The following varieties are known so far

Education and Locations

Muscovite is an important rock-forming mineral and is formed through metamorphosis , especially in mica slate or gneiss , but also magmatic in granite or pegmatite , where it can form crystals of up to 5 meters and 85 tons, such as those found in the Inikurti mine “ Emerged at Nellore in India. It occurs in many acidic deep rocks and crystalline slates , but not in effluent rocks . Weathered it, the result is by releasing potassium , a clay mineral , the illite or Hydromuskovit is called. As accompanying minerals occur, inter alia, alkali feldspar and plagioclase , biotite , quartz , topaz and tourmaline , as well as ore minerals spodumene , Amblygonit , cassiterite and Tantalit- (Mn) on.

Muscovite can be found in many places around the world, with around 13,000 known sites so far (as of 2013).

In Germany, the mineral was found in many places in the Bavarian Forest (Bodenmais, Drachselsried, Vilshofen), in the Eifel (Ettringen, Niedermendig, Niederzissen), in the Eppstein slate of the Vordertaunus , in the Ore Mountains (Ehrenfriedersdorf, Freiberg, Oberlausitz), in Fichtelgebirge (Tröstau, Weißenstadt), in the Harz (Bad Harzburg), in the Münchberger Gneismasse , in the Upper Palatinate Forest (Waidhaus), in the Odenwald (Reichelsheim), in the Black Forest (Hornberg, Wittichen), in the Siegerland , in the Spessart , in the Thuringian Forest ( Gottlob, Henneberg) and in Vogtland (Lengenfeld).

In Austria, muscovite has so far been found mainly in Carinthia (Hüttenberg, Gurktal Alps, Hohe Tauern), Salzburg (Nassfeldtal, Habachtal, Untersulzbachtal), Styria (Fischbacher Alpen, Koralpe) and Tyrol (Kalstal, Zemmgrund, Zillertal).

In Switzerland, the mineral was found mainly in the cantons of Graubünden (front and rear Rhine valleys), Ticino (Valle Maggia, Valle Leventina) and Valais (Binn ​​valley).

Beautifully developed crystal steps of up to 10 centimeters in size are also known from the Alabashka pegmatites near Murzinka ( Sverdlovsk Oblast ) in the Urals.

use

Fuchsite pendant

Because of its good thermal and electrical insulation, muscovite is an important raw material in the technical industry. In the past it was also often used for heat-resistant furnace windows and in Russia for glazing ( Moscow glass ).

Finely ground it serves (also with other types of mica) as a filler and for the internal reinforcement of coating systems. Fillers based on muscovite mica have a wide range of particle sizes, ranging from 0.001 mm to 0.5 mm. In cosmetics , muscovite is used together with biotite in lipsticks and other cosmetics to give it a long-lasting shine.

The variety fuchsite (chrome muscovite) served as a green pigment in painting and is known for its use in Indian art objects from Guatemala . It is also processed into jewelry.

See also

literature

Web links

Commons : Muscovite  - collection of images, videos and audio files
Commons : Fuchsite  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . 2nd Edition. Ott Verlag, Thun 1979, ISBN 3-7225-6265-1 , p. 221 .
  2. ↑ Christof Exner: About Muskowit-Epidot-Albitkornbildung in Mauthausen Granite In: Tschermaks mineralogische und petrographische Mitteilungen Volume 4, Kapitel 1, 1954, S. 312-319 doi: 10.1007 / BF01140402
  3. ↑ Haymo Heritsch: The conditions of formation of the garnet-thistle-paragonite-muskowite-mica slate from Gaberl, Stubalpe, Weststeiermark In: Mitteilungen Naturwissenschaftlicher Verein für Steiermark Volume 113, Graz 1983, pp. 5-14 ( PDF 2.3 MB )
  4. ^ A b Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp.  814 .
  5. ↑ a b c d Muscovite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 70.9 kB )
  6. ↑ a b c d Mindat - Muscovite
  7. ^ Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  664-665 .
  8. ↑ The numbering of this axis position does not correspond to the order of the International Tables for Crystallography , because it is not listed there.
  9. ↑ a b Udo Neumann: Mineral adhesions (polymorphisms, para- and pseudomorphoses, epitaxies and twin formations) ( Memento from November 13, 2011 in the Internet Archive ). (University of Tübingen).
  10. ↑ a b Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Dörfler Natur ). Nebel Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 250 .
  11. ↑ Mindat - Number of localities for muscovite
  12. ↑ Michaela Winkelmann: Palynostratigraphic investigations on the southern edge of the Rhenish Slate Mountains (southern Taunus, southern Hunsrück). Herbert Utz Verlag, 1997, chapter 1.5.1.2 Eppsteiner slate series, p. 9 PDF
  13. ↑ wirtz-hattersheim.de: Natursteinwerk Fischbach , Fischbach (Taunus)
  14. ↑ a b c List of places where muscovite was found in the Mineralienatlas and Mindat
  15. ↑ Detlev Gysau, fillers, technology of coating . Vincentz, Hannover 2006 (§ 5.2.3 Glimmer)