Group of phyllosilicate minerals
This article is about the mineral or muffin. For other uses, see Mica ( disambiguation )
Sheets of mica Photomicrographs of a thin section containing phlogopite. In cross-polarized light on left, plane-polarized light on right. Dark mica from Eastern Ontario

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Micas ( MY-kəz ) are a group of minerals whose great physical characteristic is that individual mica crystals can well be split into highly flimsy rubber band plates. This characteristic is described as perfect basal cleavage. Mica is common in fiery and metamorphic rock and is occasionally found as little flakes in sedimentary rock. [ 5 ] It is particularly big in many granites, pegmatites, and schists, and “ books ” ( large individual crystals ) of mica several feet across have been found in some pegmatites. [ 7 ] mica are used in products ranging from drywalls, paints, fillers, particularly in parts for automobiles, roofing and shingles, angstrom well as in electronics. The mineral is used in cosmetics to add “ shimmer ” or “ frost. ”

Properties and structure [edit ]

The mica group includes 37 phyllosilicate minerals. All clear in the monoclinic system, with a tendency towards pseudohexagonal crystals, and are similar in social organization but vary in chemical typography. Micas are translucent to opaque with a distinct glassy or chopper shininess, and different mica minerals display colors ranging from white to green or red to black. Deposits of mica tend to have a flaky or platy appearance. The crystal structure of mica is described as TOT-c, meaning that it is composed of analogue TOT layers decrepit bonded to each other by cations ( c ). The TOT layers in turn dwell of two tetrahedral sheets ( T ) strongly bonded to the two faces of a single octahedral sheet ( O ). It is the relatively watery ionic bind between TOT layers that gives mica its perfect basal cleavage. The tetrahedral sheets consist of silica tetrahedron, which are silicon ions surrounded by four oxygen ions. In most mica, one in four silicon ions is replaced by an aluminum ion, while half the silicon ions are replaced by aluminum ions in brittle mica. The tetrahedron each parcel three of their four oxygen ions with neighboring tetrahedron to produce a hexangular plane. The remaining oxygen ion ( the apical oxygen ion ) is available to bond with the octahedral sheet. The octahedral sheet can be dioctahedral or trioctahedral. A trioctahedral sheet has the structure of a sheet of the mineral brucite, with magnesium or ferric cast-iron being the most common cation. A dioctahedral sail has the structure and ( typically ) the composition of a gibbsite sheet, with aluminum being the cation. apical oxygens take the rate of some of the hydroxyl ions that would be award in a brucite or gibbsite tabloid, bonding the tetrahedral sheets tightly to the octahedral sheet. Tetrahedral sheets have a potent negative agitate, since their bulk constitution is AlSi3O105-. The octahedral sail has a incontrovertible charge, since its majority typography is Al ( OH ) 2+ ( for a dioctahedral sheet with the apical sites vacant ) or M3 ( OH ) 24+ ( for a trioctahedral site with the apical sites vacant ; M represents a bivalent ion such as ferric iron or magnesium ) The combined TOT level has a remainder negative charge, since its bulk constitution is Al2 ( AlSi3O10 ) ( OH ) 2− or M3 ( AlSi3O10 ) ( OH ) 2−. The remaining negative charge of the TOT level is neutralized by the interlayer cations ( typically sodium, potassium, or calcium ions ). Because the hexagons in the T and O sheets are slightly different in size, the sheets are slenderly distorted when they bond into a TOT layer. This breaks the hexangular symmetry and reduces it to monoclinic symmetry. however, the original hexahedral symmetry is discernible in the pseudohexagonal character of mica crystals .

  • view of tetrahedral sheet structure of mica. The apical oxygen ions are tinted pink .
  • view of trioctahedral sheet social organization of mica. The bind sites for apical oxygen are shown as white spheres .
  • position of trioctahedral sheet structure of mica emphasizing octahedral sites
  • horizon of dioctahedral sheet structure of mica. The dressing sites for apical oxygen are shown as white spheres .
  • opinion of dioctahedral sheet social organization of mica emphasizing octahedral sites
  • see of trioctahedral mica structure looking at surface of a single level
  • view of trioctahedral mica structure looking along sheets

classification [edit ]

chemically, mica can be given the general rule [ 12 ]

X2Y4–6Z8O20(OH, F)4,

in which

X is K, Na, or Ca or less commonly Ba, Rb, or Cs;
Y is Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li, etc.;
Z is chiefly Si or Al, but also may include Fe3+ or Ti.

structurally, micas can be classed as dioctahedral ( Y = 4 ) and trioctahedral ( Y = 6 ). If the X ion is K or Na, the mica is a common mica, whereas if the X ion is Ca, the mica is classed as a brittle mica .

Dioctahedral mica [edit ]

Brittle mica :

Trioctahedral mica [edit ]

common mica :
Brittle mica :

Interlayer-deficient mica [edit ]

very close-grained mica, which typically show more variation in ion and body of water contentedness, are informally termed “ cadaver mica ”. They include :

  • Hydro-muscovite with H3O+ along with K in the X site;
  • Illite with a K deficiency in the X site and correspondingly more Si in the Z site;
  • Phengite with Mg or Fe2+ substituting for Al in the Y site and a corresponding increase in Si in the Z site.

Sericite is the name given to very ticket, ragged grains and aggregates of ashen ( colorless ) mica .

happening and product [edit ]

Mica embedded in metamorphic rock ‘n’ roll Mica is widely distributed and occurs in fiery, metamorphic and aqueous regimes. big crystals of mica used for diverse applications are typically mined from granitic pegmatites. [ 5 ] The largest attested single crystal of mica ( phlogopite ) was found in Lacey Mine, Ontario, Canada ; it measured 10 m × 4.3 thousand × 4.3 m ( 33 foot × 14 foot × 14 foot ) and weighed about 330 tonnes ( 320 farseeing tons ; 360 short tons ). [ 15 ] Similar-sized crystals were besides found in Karelia, Russia. [ 16 ] Scrap and flake mica is produced all over the world. In 2010, the major producers were Russia ( 100,000 tonnes ), Finland ( 68,000 deoxythymidine monophosphate ), United States ( 53,000 metric ton ), South Korea ( 50,000 thymine ), France ( 20,000 thymine ) and Canada ( 15,000 thymine ). The full global production was 350,000 thyroxine, although no dependable data were available for China. Most tabloid mica was produced in India ( 3,500 metric ton ) and Russia ( 1,500 metric ton ). [ 17 ] Flake mica comes from several sources : the metamorphic rock called schist as a by-product of processing feldspar and china clay resources, from placer deposits, and from pegmatites. Sheet mica is well less abundant than eccentric and rubbish mica, and is occasionally recovered from mining rubbish and peel off mica. The most significant sources of sheet mica are pegmatite deposits. Sheet mica prices vary with grade and can range from less than $ 1 per kilogram for low-quality mica to more than $ 2,000 per kilogram for the highest timbre. [ 18 ] In Madagascar [ 19 ] and India, [ 20 ] it is besides mined artisanally, in hapless work conditions and with the aid of child parturiency .

Uses [edit ]

The commercially crucial micas are muscovite and phlogopite, which are used in a variety of applications .

utilitarian properties [edit ]

Mica ‘s respect is based on its singular physical properties : the crystalline structure of mica forms layers that can be split or delaminated into dilute sheets normally causing foliation in rocks. These sheets are chemically inert, insulator, elastic, flexible, hydrophilic, insulate, whippersnapper, platy, brooding, deflective, resilient, and range in opacity from crystalline to opaque. Mica is stable when exposed to electricity, fall, moisture, and extreme temperatures. It has superior electrical properties as an insulator and as a insulator, and can support an electrostatic field while dissipating minimal energy in the form of heat ; it can be split very thin ( 0.025 to 0.125 millimeters or flimsy ) while maintaining its electric properties, has a high insulator breakdown, is thermally stable to 500 °C ( 932 °F ), and is immune to corona discharge. Muscovite, the principal mica used by the electrical industry, is used in capacitors that are ideal for high frequency and radio receiver frequency. Phlogopite mica remains stable at higher temperatures ( to 900 °C ( 1,650 °F ) ) and is used in applications in which a combination of high-heat constancy and electrical properties is required. Muscovite and phlogopite are used in sheet and ground forms. [ 18 ]

labor mica [edit ]

The leading function of dry-ground mica in the US is in the joint compound for filling and finishing seams and blemishes in gypsum wallboard ( wallboard ). The mica acts as a filler and extender, provides a legato consistency, improves the workability of the intensify, and provides electric resistance to cracking. In 2008, joint compound accounted for 54 % of dry-ground mica consumption. In the paint diligence, grind mica is used as a paint extender that besides facilitates suspension, reduces chalking, prevents shrinking and shear of the paint film, increases the resistance of the key film to water penetration and weather and brightens the tone of color pigments. Mica besides promotes paint adhesion in aqueous and oleoresinous formulations. consumption of dry-ground mica in key, the second-ranked practice, accounted for 22 % of the dry-ground mica used in 2008. [ 18 ] ground mica is used in the well-drilling diligence as an additive to drilling fluids. The coarsely ground mica flakes help prevent the loss of circulation by sealing porous sections of the exercise hole. Well drilling muds accounted for 15 % of dry-ground mica habit in 2008. The plastics diligence used dry-ground mica as an extender and makeweight, particularly in parts for automobiles as lightweight insulating material to suppress sound and oscillation. Mica is used in fictile car dashboard and fenders as a reinforcing material, providing improved mechanical properties and increased dimensional stability, stiffness, and intensity. Mica-reinforced plastics besides have high-heat dimensional stability, reduced warpage, and the best surface properties of any filled plastic composite. In 2008, pulmonary tuberculosis of dry-ground mica in fictile applications accounted for 2 % of the grocery store. The rubberize diligence used ground mica as an inert filler and mold release compound in the fabricate of shaped arctic products such as tires and roofing. The platy texture acts as an anti-blocking, anti-sticking agent. Rubber mold lubricant accounted for 1.5 % of the dry-ground mica used in 2008. As a rubber linear, mica reduces flatulence interpenetration and improves resilience. [ 18 ] Dry-ground mica is used in the production of roll roofing and asphalt shingles, where it serves as a surface application to prevent stick of adjacent surfaces. The coating is not absorbed by newly manufactured roofing because mica ‘s platy structure is unaffected by the acid in asphalt or by weather conditions. Mica is used in cosmetic coatings on wallpaper, concrete, stucco, and tile surfaces. It besides is used as an ingredient in flux coatings on welding rods, in some extra greases, and as coatings for core and determine turn compounds, facing agents, and mold washes in foundry applications. Dry-ground phlogopite mica is used in automotive bracken linings and clutch plates to reduce noise and vibration ( asbestos substitute ) ; as sound-absorbing insulation for coatings and polymer systems ; in reinforcing additives for polymers to increase strength and stiffness and to improve constancy to heat, chemicals, and ultraviolet ( UV ) radiation ; in inflame shields and temperature insulation ; in industrial coating linear to decrease the permeability of moisture and hydrocarbons ; and in pivotal polymer formulations to increase the strength of epoxies, nylons, and polyesters. [ 18 ]

Paints and cosmetics [edit ]

Mica flakes embedded in a fresco for glitter

Wet-ground mica, which retains the brilliance of its cleavage faces, is used chiefly in iridescent paints by the automotive diligence. many metallike pigments are composed of a substrate of mica coated with another mineral, normally titanium dioxide ( TiO2 ). The vector sum pigment produces a brooding discolor depending on the thickness of the coat. These products are used to produce automobile rouge, shimmery formative containers, high-quality inks used in ad and security applications. In the cosmetics industry, its brooding and deflective properties make mica an crucial ingredient in blushes, eye liner, center shadow, foundation, hair’s-breadth and body glitter, lipstick, lip glossary, mascara, moisturizing lotions, and nail polish. Some brands of toothpaste include powdered white mica. This acts as a mild harsh to aid polish of the tooth come on, and besides adds a cosmetically pleasing, aglitter shimmer to the glue. Mica is added to latex balloons to provide a biased glazed come on. [ 18 ]

insulator [edit ]

Mica is besides used as an insulator in concrete block and home attics and can be poured into walls ( normally in retrofitting uninsulated open top walls ). Mica may besides be used as a dirt conditioner, specially in potting soil mixes and in gardening plots. Greases used for axles are composed of a compound of fatso oils to which mica, mariner or graphite is added to increase the lastingness of the dirt and give it a better come on .

Built-up mica [edit ]

Muscovite and phlogopite splittings can be fabricated into versatile built-up mica products. Produced by mechanize or hand typeset of overlapping splittings and alternate layers of binders and splittings, built-up mica is used primarily as an electric insulating material material. Mica insulation is used in high-temperature and fire-retardant world power cables in aluminum plants, blast furnaces, critical cable circuits ( for model, defense systems, arouse and security dismay systems, and surveillance systems ), heaters and boilers, lumber kiln, alloy smelters, and tanks and furnace cable. specific high-temperature mica-insulated wire and cable is rated to work for up to 15 minutes in molten aluminum, glaze, and steel. major products are bonding materials ; flexible, fastball, modeling, and segment plates ; mica newspaper ; and record. [ 18 ] elastic home plate is used in electric motor and generator armatures, field coil insulation, and attraction and commutator core insulation. Mica consumption in flexible plate was about 21 tonnes in 2008 in the US. Heater plate is used where high-temperature insulation is required. Molding denture is sheet mica from which V-rings are cut and stamped for use in insulating the copper segments from the steel shaft ends of a commutator. Molding plate is besides fabricated into tubes and rings for insulating material in armatures, motive starters, and transformers. segment plate acts as insulating material between the copper commutator segments of direct-current universal motors and generators. Phlogopite built-up mica is preferred because it wears at the same rate as the bull segments. Although muscovite has a greater resistance to wear, it causes mismatched ridges that may interfere with the operation of a drive or generator. consumption of segment plate was about 149 t in 2008 in the US. Some types of built-up mica have the bonded splittings reinforced with fabric, glass, linen, muslin, plastic, silk, or especial paper. These products are identical flexible and are produced in across-the-board, continuous sheets that are either ship, rolled, or cut into ribbons or tapes, or trimmed to specified dimensions. Built-up mica products may besides be corrugated or reinforced by multiple layer. In 2008, about 351 t of built-up mica was consumed in the US, largely for molding plates ( 19 % ) and segment plates ( 42 % ). [ 18 ]

Sheet mica [edit ]

Muscovite windows technical grade sheet mica is used in electric components, electronics, in nuclear power microscopy and as window sheets. other uses include diaphragms for oxygen-breathing equipment, marker dials for seafaring compasses, ocular filters, pyrometers, thermal regulators, stave and kerosene heater windows, radiation aperture covers for microwave ovens, and micathermic heater elements. Mica is birefringent and is therefore normally used to make quarter and one-half wave plates. Specialized applications for sheet mica are found in aerospace components in air-, ground-, and sea-launched projectile systems, laser devices, aesculapian electronics and radar systems. Mica is mechanically stable in micrometer-thin sheets which are relatively crystalline to radiation ( such as alpha particles ) while being impervious to most gases. It is therefore used as a windowpane on radiation detectors such as Geiger–Müller tube. In 2008, mica splittings represented the largest share of the plane mica industry in the United States. Consumption of muscovite and phlogopite splittings was about 308 t in 2008. Muscovite splittings from India accounted for basically all US pulmonary tuberculosis. The remainder was primarily imported from Madagascar. [ 18 ] little squared pieces of sheet mica are besides used in the traditional japanese Kōdō ceremony to burn cense : A burning piece of coal is placed inside a cone made of white ash. The sheet of mica is placed on crown, acting as a centrifuge between the heat reservoir and the incense, in holy order to spread the aroma without burning it .

electric and electronic [edit ]

Micanite or mica for isolated mount of transistors ( crown, right ) and mica disk. Sheet mica is used chiefly in the electronic and electrical industries. Its utility in these applications is derived from its alone electric and thermal properties and its mechanical properties, which allow it to be cut, punched, stamped, and machined to close tolerances. specifically, mica is strange in that it is a good electrical insulator at the lapp fourth dimension as being a good thermal conductor. The leading use of freeze mica is as an electrical insulator in electronic equipment. High-quality engine block mica is processed to line the gauge glasses of hard-hitting steam boilers because of its tractability, transparency, and underground to heat and chemical attack. alone high-quality muscovite film mica, which is variously called India ruby mica or ruby muscovite mica, is used as a insulator in capacitors. The highest quality mica film is used to manufacture capacitors for calibration standards. The next lower rate is used in transmitting capacitors. Receiving capacitors use a slightly lower grade of high-quality muscovite. [ 18 ] Mica sheets are used to provide structure for heating wire ( such as in Kanthal or Nichrome ) in heating elements and can withstand up to 900 °C ( 1,650 °F ) .

Atomic force microscopy [edit ]

Another use of mica is as a substrate in the production of ultraflat, thin-film surfaces, e.g. aureate surfaces. Although the situate film surface is even grating ascribable to deposition kinetics, the back side of the film at the mica-film interface is ultraflat once the movie is removed from the substrate. Freshly-cleaved mica surfaces have been used as clean imaging substrates in atomic force out microscopy, [ 21 ] enabling for model the imaging of bismuth films, [ 22 ] plasma glycoproteins, [ 23 ] membrane bilayers, [ 24 ] and DNA molecules. [ 25 ]

Peepholes [edit ]

Thin diaphanous sheets of mica were used for peepholes in boilers, lanterns, stoves, and kerosene heaters because they were less likely to shatter than glass when exposed to extreme temperature gradients. such peepholes were besides used in “ mica curtains ” in horse-drawn carriages [ 26 ] and early 20th-century cars. [ 27 ]

etymology [edit ]

The bible mica is derived from the Latin parole mica, meaning a crumb, and credibly influenced by micare, to glitter. [ 28 ]

early history [edit ]

Human use of mica dates back to prehistoric times. Mica was known to ancient indian, egyptian, Greek, Roman, and chinese civilizations, a well as the Aztec civilization of the New World. [ 29 ] The earliest use of mica has been found in cave paintings created during the Upper Paleolithic period ( 40,000 BC to 10,000 BC ). The first hues were crimson ( iron oxide, hematite, or loss ocher ) and black ( manganese dioxide, pyrolusite ), though black from juniper or pine carbons has besides been discovered. White from china clay or mica was used occasionally. A few kilometers northeastern of Mexico City stands the ancient site of Teotihuacan. The most fall upon structure of Teotihuacan is the towering Pyramid of the Sun. The pyramid contained considerable amounts of mica in layers up to 30 centimeter ( 12 in ) blockheaded. [ 30 ] Natural mica was and still is used by the Taos and Picuris Pueblos Indians in north-central New Mexico to make pottery. The pottery is made from weather Precambrian mica schist, and has flecks of mica throughout the vessels. Tewa Pueblo pottery is made by coating the clay with mica to provide a dense, aglitter micaceous stopping point over the entire object. [ 18 ] Mica flakes ( called abrak in Urdu and written as ابرک ) are besides used in Pakistan to embellish women ‘s summer clothes, particularly dupattas ( retentive light-weight scarves, much colorful and matching the dress ). [ 31 ] [ 32 ] Thin mica flakes are added to a hot starch water solution, and the dupatta is dipped in this water concoction for 3–5 minutes. then it is hung to air dry .

Mica powder [edit ]

Kirazuri printing technique adds mica powder to the gelatin solution as adhesive, here printed on the background.[33] print technique adds mica powder to the gelatin solution as adhesive, hera printed on the background. Throughout the ages, very well powders of mica have been used for diverse purposes, including decorations. Powdered mica glitter is used to decorate traditional water mud pots in India, Pakistan and Bangladesh ; it is besides used on traditional Pueblo pottery, though not restricted to use on water pots in this case. The gulal and abir ( color powders ) used by North amerind Hindus during the gay season of Holi contain all right crystals of mica to create a spark impression. The gallant Padmanabhapuram Palace, 65 kilometer ( 40 security service ) from Trivandrum in India, has colored mica windows. Mica powder is besides used as a decoration in traditional japanese woodblock printmaking, [ 34 ] as when applied to wet ink with gelatin as thickening using kirazuri proficiency and allowed to dry, it sparkles and reflects light. Earlier examples are found among newspaper decorations, with the stature as the Nishi Honganji 36 Poets Collection, codices of illuminate manuscripts in and after ACE 1112. For metallic glitter, Ukiyo-e prints employed identical compact solution either with or without color pigments stenciled on hairpins, sword blades or fish scales on cavil streamers ( 鯉のぼり, Koinobori ). The dirty around Nishio in cardinal Japan is rich in mica deposits, which was already mined in the Nara menstruation. Yatsuomote merchandise is a type of local anesthetic japanese pottery from there. After an incidental at Mount Yatsuomote a small doorbell was offered to soothe the kami. Katō Kumazō started a local tradition where little ceramic zodiac bells ( きらら鈴 ) were made out of local mica kneaded into the cadaver, and after burning in the kiln the bell would make a please strait when call. [ 35 ] [ 36 ] [ 37 ]

medicine [edit ]

Ayurveda, the Hindu arrangement of ancient medicate prevailing in India, includes the purification and process of mica in preparing Abhraka bhasma, which is claimed as a treatment for diseases of the respiratory and digestive tracts. [ 38 ] [ 39 ]

Health impact [edit ]

Mica dust in the workplace is regarded as a hazardous message for respiratory photograph above certain concentrations .

United States [edit ]

The Occupational Safety and Health Administration ( OSHA ) has set the legal restrict ( permissible vulnerability terminus ad quem ) for mica exposure in the workplace as 20 million parts per cubic metrical foot ( 706,720,000 parts per cubic meter ) over an 8-hour workday. The National Institute for Occupational Safety and Health ( NIOSH ) has set a recommend exposure restrict ( REL ) of 3 mg/m3 respiratory exposure over an 8-hour workday. At levels of 1,500 mg/m3, mica is immediately dangerous to life sentence and health. [ 40 ]

Substitutes [edit ]

Some lightweight aggregates, such as diatomaceous earth, perlite, and vermiculite, may be substituted for land mica when used as filler. Ground man-made fluorophlogopite, [ 41 ] a fluorine-rich mica, may replace natural reason mica for uses that require thermal and electric properties of mica. many materials can be substituted for mica in numerous electric, electronic, and insulation uses. Substitutes include propenoate polymers, cellulose acetate, fiberglass, fishpaper, nylon, phenolics, polycarbonate, polyester, styrene, vinyl-PVC, and vulcanized roughage. Mica paper made from bit mica can be substituted for sheet mica in electric and insulation applications. [ 17 ]

See besides [edit ]

References [edit ]

Sources [edit ]