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Muscovite (also known as common mica, isinglass, or potash mica) is a hydrated
phyllosilicate Silicate minerals are rock-forming mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology) ...

phyllosilicate
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

mineral
of
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

aluminium
and
potassium Potassium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

potassium
with formula
K
K
Al
Al
2(Al
Si
Si
3
O
O
10)(
F
F
,O
H
H
)2, or (
KF
KF
)2( Al2O3)3( SiO2)6( H2O). It has a highly perfect basal cleavage yielding remarkably thin laminae (sheets) which are often highly elastic. Sheets of muscovite 5 meters × 3 meters (16.5 feet × 10 feet) have been found in
Nellore Nellore is a city located on the banks of Penna River Penna (also known as Pennar, Penner, Penneru, and Uttara Pinakini) is a river of southern India India (Hindi: ), officially the Republic of India (Hindi: ), is a country in South Asi ...
,
India India, officially the Republic of India (Hindi Hindi (Devanagari: , हिंदी, ISO 15919, ISO: ), or more precisely Modern Standard Hindi (Devanagari: , ISO 15919, ISO: ), is an Indo-Aryan language spoken chiefly in Hindi Belt, ...

India
. Muscovite has a
Mohs hardness The Mohs scale of mineral hardness () is a Qualitative property, qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was creat ...
of 2–2.25 parallel to the
01
01
face, 4 perpendicular to the
01
01
and a
specific gravity Relative density, or specific gravity, is the ratio In mathematics, a ratio indicates how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemon ...
of 2.76–3. It can be colorless or tinted through grays,
brown Brown is a composite color Color (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United State ...

brown
s,
green Green is the color between blue and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 Nanometre, nm. In subtractive color systems, used in painting and color printing, it is created by ...

green
s,
yellow Yellow is the color between green and Orange (colour), orange on the Visible spectrum, spectrum of visible light. It is evoked by light with a dominant wavelength of roughly 575585 Nanometre, nm. It is a primary color in subtractive color syst ...

yellow
s, or (rarely)
violet Violet may refer to: Common meanings * Violet (color), a spectral color with wavelengths shorter than blue * One of a list of plants known as violet, particularly: ** Viola (plant), ''Viola'' (plant), a genus of flowering plants Places United ...
or
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength Image:dominant wavelength.png, frame, Dominant/complementary wavelength example on the CIE color ...

red
, and can be transparent or translucent. It is
anisotropic Anisotropy () is the property of a material which allows it to change or assume different properties in different directions as opposed to isotropy Isotropy is uniformity in all orientations; it is derived from the Greek ''isos'' (ἴσος, ...
and has high
birefringence Birefringence is the property of a material having a that depends on the and propagation direction of . These optically materials are said to be birefringent (or birefractive). The birefringence is often quantified as the maximum difference b ...

birefringence
. Its crystal system is
monoclinic In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek language, Greek words ''crystallon'' " ...

monoclinic
. The green,
chromium Chromium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science tha ...

chromium
-rich variety is called
fuchsite Fuchsite, also known as chrome mica, is a chromium (Cr) rich variety of the mineral muscovite, belonging to the mica group of phyllosilicate minerals, with the chemical formula . Trivalency, Trivalent chromium replaces one of the aluminium (Al) ato ...

fuchsite
; mariposite is also a
chromium Chromium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science tha ...

chromium
-rich type of muscovite. Muscovite is the most common
mica Micas ( ) are a group of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs natural ...

mica
, found in
granite Granite () is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cool ...

granite
s,
pegmatite A pegmatite is an igneous rock showing a very coarse Texture (geology), texure, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a si ...
s,
gneiss Gneiss ( ) is a common and widely distributed type of metamorphic rock Metamorphic rocks arise from the transformation of existing rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or ag ...

gneiss
es, and
schist Schist ( ) is a medium-grained metamorphic rock , a type of metamorphic rock Metamorphic rocks arise from the transformation of existing rock (geology), rock to new types of rock, in a process called metamorphism upright=1.35, Schematic r ...

schist
s, and as a contact
metamorphic rock Metamorphic rocks arise from the transformation of existing rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the mineral ...

metamorphic rock
or as a secondary
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

mineral
resulting from the alteration of
topaz Topaz ( ) is a silicate mineral Silicate minerals are rock-forming mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with ...

topaz
,
feldspar Feldspars are a group of rock-forming aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity ...
,
kyanite Kyanite is a typically blue aluminosilicate Aluminosilicate mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid ...

kyanite
, etc. It is characteristic of
peraluminous rock Peraluminous rocks are igneous rock Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area arou ...
, in which the content of aluminum is relatively high. In pegmatites, it is often found in immense sheets that are commercially valuable. Muscovite is in demand for the manufacture of
fireproofing Fireproofing is rendering something (structures A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting or interrelated elements that act accor ...

fireproofing
and insulating materials and to some extent as a
lubricant A lubricant is a substance that helps to reduce friction Friction is the force In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and b ...
.


Naming

The name muscovite comes from ''Muscovy-glass'', a name given to the mineral in
Elizabethan England The Elizabethan era is the epoch in the Tudor period The Tudor period occurred between 1485 and 1603 in England and Wales England and Wales () is a legal jurisdiction covering England and Wales, two of the four countries of the United King ...
due to its use in medieval
Russia Russia ( rus, link=no, Россия, Rossiya, ), or the Russian Federation, is a country spanning Eastern Europe Eastern Europe is the eastern region of . There is no consistent definition of the precise area it covers, partly because th ...

Russia
(
Muscovy Muscovy is an alternative name for the Grand Duchy of Moscow The Grand Duchy of Moscow, Muscovite Russia, Muscovite Rus' or Grand Principality of Moscow (russian: Великое княжество Московское, Velikoye knyazhestvo Mosk ...
) as a cheaper alternative to
glass Glass is a non- crystalline, often transparency and translucency, transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by ...

glass
in windows. This usage became widely known in
England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest of England and the Celtic Sea to the southwest. E ...

England
during the sixteenth century with its first mention appearing in letters by
George Turberville George Turberville, or Turbervile (about 1540 - before 1597) was an England, English poet. Life He was the second son of Henry Turberville of Winterborne Whitechurch, Dorset, and nephew of James Turberville, Bishop of Exeter. The Turbervilles were ...
, the secretary of England's ambassador to the
Muscovite Muscovite (also known as common mica, isinglass, or potash mica) is a hydrated phyllosilicate Silicate minerals are rock-forming mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'' ...
tsar Tsar ( or ), also spelled ''czar'', ''tzar'', or ''csar'', is a Royal and noble ranks, title used to designate Orthodox Slavs, East and South Slavic monarchs. In this last capacity it lends its name to a system of government, tsarist autocra ...

tsar
Ivan the Terrible Ivan IV Vasilyevich (russian: Ива́н Васильевич; 25 August 1530 – ), commonly known in English language, English as Ivan the Terrible (from , Romanization of Russian, romanized: , Literal translation, lit. "Ivan the Formidable ...
, in 1568.


Distinguishing characteristics

Micas are distinguished from other minerals by their pseudohexagonal crystal shape and their perfect cleavage, which allows the crystals to be pulled apart into very thin elastic sheets.
Pyrophyllite Pyrophyllite is a phyllosilicate Silicate minerals are rock-forming mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with t ...

Pyrophyllite
, and
talc Talc, or talcum, is a clay mineral Clay minerals are , sometimes with variable amounts of , , s, s, and other s found on or near some s. Clay minerals form in the presence of water and have been important to life, and many theories of ...

talc
are softer than micas and have a greasy feel, while
chlorite The chlorite ion An ion () is a particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can be ascribed several physical ...

chlorite
is green in color and its cleavage sheets are inelastic. The other common mica mineral,
biotite Biotite is a common group of Silicate minerals#Phyllosilicates, phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid solution, solid-solution series between the iron-endmember annite, and ...

biotite
, is almost always much darker in color than muscovite.
Paragonite Paragonite is a mineral, related to muscovite. Its empirical formula is sodium, Naaluminum, Al2 Ohydrogen, H)2, Alsilicon, Si3oxygen, O10 A wide solvus separates muscovite from paragonite, such that there is little solid solution along the vect ...
can be difficult to distinguish from muscovite but is much less common, though it is likely mistaken for muscovite often enough that it may be more common that is generally appreciated.


Composition and structure

Like all
mica Micas ( ) are a group of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs natural ...

mica
minerals, muscovite is a
phyllosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide) is usually conside ...
(sheet silicate) mineral with a ''TOT-c'' structure. In other words, a crystal of muscovite consists of layers (''TOT'') bonded to each other by
potassium Potassium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

potassium
cations An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are u ...

cations
(''c''). Each layer is composed of three sheets. The outer sheets ('T' or tetrahedral sheets) consist of
silicon Silicon is a chemical element with the Symbol (chemistry), symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a Tetravalence, tetravalent metalloid and semiconductor. It is a member ...

silicon
or
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

aluminium
cations, each surrounded by four oxygen
anions An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ...

anions
forming a tetrahedron around the cation, with three of the oxygen anions shared with neighboring tetrahedra to form a hexagonal sheet. The fourth oxygen anion in each tetrahedral sheet is called an ''apical'' oxygen anion. There are three silicon cations for each aluminium cation but the arrangement of aluminium and silicon cations is largely disordered. The middle octahedral (''O'') sheet consists of aluminium cations that are each surrounded by six oxygen or
hydroxide Hydroxide is a diatomic anion with chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other sym ...
anions forming an octahedron, with the octahedrons sharing anions to form a hexagonal sheet similar to the tetrahedral sheets. The apical oxygen anions of the outer ''T'' sheets face inwards and are shared by the octahedral sheet, binding the sheets firmly together. The relatively strong binding between oxygen anions and aluminium and silicon cations within a layer, compared with the weaker binding of potassium cations between layers, gives muscovite its pefect basal cleavage. In muscovite, alternate layers are slightly offset from each other, so that the structure repeats every two layers. This is called the 1''M'' polytype of the general mica structure. File:Mica T.png, View of tetrahedral sheet of muscovite. The apical oxygen ions are tinted pink. File:Mica dO.png, View of octahedral sheet of muscovite. The binding sites for apical oxygen are shown as white spheres. File:Mica dOs.png, View of octahedral sheet of muscovite with ion sizes altered to emphasizing octahedral sites File:Muscovite structure 100.jpg, Structure of muscovite, viewed in the direction (along the layers of the crystal) The formula for muscovite is typically given as , but it is common for small amounts of other elements to substitute for the main constituents.
Alkali metal The alkali metals consist of the chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structur ...
s such as
sodium Sodium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical eleme ...

sodium
,
rubidium Rubidium is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science th ...

rubidium
, and
caesium Caesium (IUPAC spelling) (American and British English spelling differences, also spelled cesium in American English) is a chemical element with the Symbol (chemistry), symbol Cs and atomic number 55. It is a soft, silvery-golden alkal ...

caesium
substitute for potassium;
magnesium Magnesium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

magnesium
,
iron Iron () is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behav ...

iron
,
lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: the ...

lithium
,
chromium Chromium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science tha ...

chromium
,
titanium Titanium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical ele ...

titanium
, or
vanadium Vanadium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science tha ...

vanadium
can substitute for aluminium in the octahedral sheet;
fluorine Fluorine is a chemical element with the Chemical symbol, symbol F and atomic number 9. It is the lightest halogen and exists at Standard conditions for temperature and pressure, standard conditions as a highly toxic, pale yellow Diatomic molecule ...

fluorine
or
chlorine Chlorine is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemica ...

chlorine
can substitute for hydroxide; and the ratio of aluminium to silicon in the tetrahedral sheets can change to maintain charge balance where necessary (as when magnesium cations, with a charge of +2, substitute for aluminium ions, with a charge of +3). Up to 10% of the potassium may be replaced by sodium, and up to 20% of the hydroxide by fluorine. Chorine rarely replaces more than 1% of the hydroxide. Muscovite in which the mole fraction of silicon is greater than aluminium, and magnesium or iron replaces some of the aluminium to maintain charge balance, is called
phengite Phengite is a series name for dioctahedral micas of composition K(AlMg)2(OH)2(SiAl)4O10 it is common for Mg or Fe2+ to substitute for Al on the Y site and a corresponding increase in Si on the Z site in the mica group formula ''X''2''Y''4–6''Z'' ...
.


Uses

Muscovite can be cleaved into very thin transparent sheets that can substitute for glass, particularly for high-temperature applications such as industrial furnace or oven windows. It is also used in the manufacture of a wide variety of electronics and as a filler in paints, plastic, and wallboard. It lends a silky luster to
wallpaper Wallpaper is a material used in interior decoration Interior design is the art and science of enhancing the interior of a building to achieve a healthier and more aesthetically pleasing environment for the people using the space. An inter ...

wallpaper
. It is also used in
tire A tire (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United States ...

tire
manufacture as a mold release agent, in
drilling mud In geotechnical engineering, drilling fluid, also called drilling mud, is used to aid the drilling of boreholes into the earth. Often used while drilling oil well, oil and natural gas wells and on exploration drilling rigs, drilling fluids a ...
, and in various
cosmetics Cosmetics are constituted mixtures of chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and take ...
for its luster.


Gallery

File:Beryl-Muscovite-171688.jpg, Muscovite with
beryl Beryl ( ) is a mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which i ...

beryl
(var. morganite) from Paprok, Afghanistan File:Alurgite St Marcel.jpg, Muscovite (var. alurgite), from Prabornaz Mine, Aosta Valley, Italy File:Muscovite crystals.JPG, Tabular muscovite crystals in a gneiss in
thin section vein in mica Micas ( ) are a group of minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect Cleavage (crystal) ...
viewed under cross-polarized light at 2x magnification.


References


External links

* {{Authority control Potassium minerals Aluminium minerals Mica group Monoclinic minerals Minerals in space group 15 Potash Medieval Russian architecture Windows