The mica group of sheet silicate (phyllosilicate) minerals includes several closely related materials having nearly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition. The nearly perfect cleavage, which is the most prominent characteristic of mica, is explained by the hexagonal sheet-like arrangement of its atoms.

The word mica is derived from the Latin word mica, meaning a crumb, and probably influenced by micare, to glitter.[5]

Mica (6911818878)
(repeating unit)
AB2–3(X, Si)4O10(O, F, OH)2
Colorpurple, rosy, silver, gray (lepidolite); dark green, brown, black (biotite); yellowish-brown, green-white (phlogopite); colorless, transparent (muscovite)
CleavageAlmost perfect
Mohs scale hardness2.5–4 (lepidolite); 2.5–3 biotite; 2.5–3 phlogopite; 2–2.5 muscovite
Lusterpearly, vitreous
StreakWhite, colorless
Specific gravity2.8–3.0
Diagnostic featurescleavage
Sheet mica
Mica flakes
Dark Mica from Eastern Ontario
Dark mica from Eastern Ontario


Chemically, micas can be given the general formula[6]

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 micas

Trioctahedral micas

Common micas:

Brittle micas:

Interlayer-deficient micas

Very fine-grained micas, which typically show more variation in ion and water content, are informally termed "clay micas". 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.

Occurrence and production

Mica embedded in metamorphic rock

Mica is widely distributed and occurs in igneous, metamorphic and sedimentary regimes. Large crystals of mica used for various applications are typically mined from granitic pegmatites.

Until the 19th century, large crystals of mica were quite rare and expensive as a result of the limited supply in Europe. However, their price dramatically dropped when large reserves were found and mined in Africa and South America during the early 19th century. The largest documented single crystal of mica (phlogopite) was found in Lacey Mine, Ontario, Canada; it measured 10 m × 4.3 m × 4.3 m (33 ft × 14 ft × 14 ft) and weighed about 330 tonnes (320 long tons; 360 short tons).[8] Similar-sized crystals were also found in Karelia, Russia.[9]

The British Geological Survey reported that as of 2005, Koderma district in Jharkhand state in India had the largest deposits of mica in the world. China was the top producer of mica with almost a third of the global share, closely followed by the US, South Korea and Canada. Large deposits of sheet mica were mined in New England from the 19th century to the 1970s. Large mines existed in Connecticut, New Hampshire, and Maine.

Scrap and flake mica is produced all over the world. In 2010, the major producers were Russia (100,000 tonnes), Finland (68,000 t), United States (53,000 t), South Korea (50,000 t), France (20,000 t) and Canada (15,000 t). The total global production was 350,000 t, although no reliable data were available for China. Most sheet mica was produced in India (3,500 t) and Russia (1,500 t).[10] Flake mica comes from several sources: the metamorphic rock called schist as a byproduct of processing feldspar and kaolin resources, from placer deposits, and from pegmatites. Sheet mica is considerably less abundant than flake and scrap mica, and is occasionally recovered from mining scrap and flake mica. The most important 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 quality.[11]

Properties and uses

The mica group represents 37 phyllosilicate minerals that have a layered or platy texture. The commercially important micas are muscovite and phlogopite, which are used in a variety of applications. Mica’s value is based on several of its unique physical properties. The crystalline structure of mica forms layers that can be split or delaminated into thin sheets usually causing foliation in rocks. These sheets are chemically inert, dielectric, elastic, flexible, hydrophilic, insulating, lightweight, platy, reflective, refractive, resilient, and range in opacity from transparent to opaque. Mica is stable when exposed to electricity, light, moisture, and extreme temperatures. It has superior electrical properties as an insulator and as a dielectric, 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 thinner) while maintaining its electrical properties, has a high dielectric breakdown, is thermally stable to 500 °C (932 °F), and is resistant to corona discharge. Muscovite, the principal mica used by the electrical industry, is used in capacitors that are ideal for high frequency and radio 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 stability and electrical properties is required. Muscovite and phlogopite are used in sheet and ground forms.[11]

Ground mica

The leading use of dry-ground mica in the US is in the joint compound for filling and finishing seams and blemishes in gypsum wallboard (drywall). The mica acts as a filler and extender, provides a smooth consistency, improves the workability of the compound, and provides resistance to cracking. In 2008, joint compound accounted for 54% of dry-ground mica consumption. In the paint industry, ground mica is used as a pigment extender that also facilitates suspension, reduces chalking, prevents shrinking and shearing of the paint film, increases the resistance of the paint film to water penetration and weathering and brightens the tone of colored pigments. Mica also promotes paint adhesion in aqueous and oleoresinous formulations. Consumption of dry-ground mica in paint, the second-ranked use, accounted for 22% of the dry-ground mica used in 2008.[11]

Ground mica is used in the well-drilling industry as an additive to drilling fluids. The coarsely ground mica flakes help prevent the loss of circulation by sealing porous sections of the drill hole. Well drilling muds accounted for 15% of dry-ground mica use in 2008. The plastics industry used dry-ground mica as an extender and filler, especially in parts for automobiles as lightweight insulation to suppress sound and vibration. Mica is used in plastic automobile fascia and fenders as a reinforcing material, providing improved mechanical properties and increased dimensional stability, stiffness, and strength. Mica-reinforced plastics also have high-heat dimensional stability, reduced warpage, and the best surface properties of any filled plastic composite. In 2008, consumption of dry-ground mica in plastic applications accounted for 2% of the market. The rubber industry used ground mica as an inert filler and mold release compound in the manufacture of molded rubber 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 additive, mica reduces gas permeation and improves resiliency.[11]

Dry-ground mica is used in the production of rolled roofing and asphalt shingles, where it serves as a surface coating to prevent sticking of adjacent surfaces. The coating is not absorbed by freshly manufactured roofing because mica’s platy structure is unaffected by the acid in asphalt or by weather conditions. Mica is used in decorative coatings on wallpaper, concrete, stucco, and tile surfaces. It also is used as an ingredient in flux coatings on welding rods, in some special greases, and as coatings for core and mold release compounds, facing agents, and mold washes in foundry applications. Dry-ground phlogopite mica is used in automotive brake 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 stability to heat, chemicals, and ultraviolet (UV) radiation; in heat shields and temperature insulation; in industrial coating additive to decrease the permeability of moisture and hydrocarbons; and in polar polymer formulations to increase the strength of epoxies, nylons, and polyesters.[11]

Mica flakes embedded in a fresco for glitter

Wet-ground mica, which retains the brilliance of its cleavage faces, is used primarily in pearlescent paints by the automotive industry. Many metallic-looking pigments are composed of a substrate of mica coated with another mineral, usually titanium dioxide (TiO2). The resultant pigment produces a reflective color depending on the thickness of the coating. These products are used to produce automobile paint, shimmery plastic containers, high-quality inks used in advertising and security applications. In the cosmetics industry, its reflective and refractive properties make mica an important ingredient in blushes, eye liner, eye shadow, foundation, hair and body glitter, lipstick, lip gloss, mascara, moisturizing lotions, and nail polish. Some brands of toothpaste include powdered white mica. This acts as a mild abrasive to aid polishing of the tooth surface, and also adds a cosmetically pleasing, glittery shimmer to the paste. Mica is added to latex balloons to provide a colored shiny surface.[11]

Mica is also used as an insulator in concrete block and home attics and can be poured into walls (usually in retrofitting uninsulated open top walls). Mica may also be used as a soil conditioner, especially in potting soil mixes and in gardening plots. Greases used for axles are composed of a compound of fatty oils to which mica, tar or graphite is added to increase the durability of the grease and give it a better surface.

Built-up mica

Muscovite and phlogopite splittings can be fabricated into various built-up mica products. Produced by mechanized or hand setting of overlapping splittings and alternate layers of binders and splittings, built-up mica is used primarily as an electrical insulation material. Mica insulation is used in high-temperature and fire-resistant power cables in aluminium plants, blast furnaces, critical wiring circuits (for example, defense systems, fire and security alarm systems, and surveillance systems), heaters and boilers, lumber kilns, metal smelters, and tanks and furnace wiring. Specific high-temperature mica-insulated wire and cable is rated to work for up to 15 minutes in molten aluminium, glass, and steel. Major products are bonding materials; flexible, heater, molding, and segment plates; mica paper; and tape.[11]

Flexible plate is used in electric motor and generator armatures, field coil insulation, and magnet 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 plate 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 also fabricated into tubes and rings for insulation in armatures, motor starters, and transformers. Segment plate acts as insulation 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 copper segments. Although muscovite has a greater resistance to wear, it causes uneven ridges that may interfere with the operation of a motor 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 cloth, glass, linen, muslin, plastic, silk, or special paper. These products are very flexible and are produced in wide, continuous sheets that are either shipped, rolled, or cut into ribbons or tapes, or trimmed to specified dimensions. Built-up mica products may also be corrugated or reinforced by multiple layering. In 2008, about 351 t of built-up mica was consumed in the US, mostly for molding plates (19%) and segment plates (42%).[11]

Sheet mica

Mica insulator items
Silver mica capacitors
Silver mica capacitors
Muscovite window
Muscovite windows

Technical grade sheet mica is used in electrical components, electronics, in atomic force microscopy and as window sheets. Other uses include diaphragms for oxygen-breathing equipment, marker dials for navigation compasses, optical filters, pyrometers, thermal regulators, stove and kerosene heater windows, radiation aperture covers for microwave ovens, and micathermic heater elements. Mica is birefringent and is therefore commonly used to make quarter and half wave plates. Specialized applications for sheet mica are found in aerospace components in air-, ground-, and sea-launched missile systems, laser devices, medical electronics and radar systems. Mica is mechanically stable in micrometer-thin sheets which are relatively transparent to radiation (such as alpha particles) while being impervious to most gases. It is therefore used as a window on radiation detectors such as Geiger-Müller tubes.

In 2008, mica splittings represented the largest part of the sheet mica industry in the United States. Consumption of muscovite and phlogopite splittings was about 308 t in 2008. Muscovite splittings from India accounted for essentially all US consumption. The remainder was primarily imported from Madagascar.[11]

Small squared pieces of sheet mica are also used in the traditional Japanese Kodo ceremony to burn incense: A burning piece of coal is placed inside a cone made of white ash. The sheet of mica is placed on top, acting as a separator between the heat source and the incense, in order to spread the fragrance without burning it.

Electrical and electronic

Sheet mica is used principally in the electronic and electrical industries. Its usefulness in these applications is derived from its unique electrical and thermal properties and its mechanical properties, which allow it to be cut, punched, stamped, and machined to close tolerances. Specifically, mica is unusual in that it is a good electrical insulator at the same time as being a good thermal conductor. The leading use of block mica is as an electrical insulator in electronic equipment. High-quality block mica is processed to line the gauge glasses of high-pressure steam boilers because of its flexibility, transparency, and resistance to heat and chemical attack. Only high-quality muscovite film mica, which is variously called India ruby mica or ruby muscovite mica, is used as a dielectric in capacitors. The highest quality mica film is used to manufacture capacitors for calibration standards. The next lower grade is used in transmitting capacitors. Receiving capacitors use a slightly lower grade of high-quality muscovite.[11]

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).


Thin transparent 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 also used in "isinglass curtains" in horse-drawn carriages[12] and early 20th-century cars.[13]

Atomic force microscopy

Another use of mica is as a substrate in the production of ultraflat, thin-film surfaces, e.g. gold surfaces. Although the deposited film surface is still rough due to deposition kinetics, the back side of the film at the mica-film interface is ultraflat once the film is removed from the substrate. Freshly-cleaved mica surfaces have been used as clean imaging substrates in atomic force microscopy,[14] enabling for example the imaging of bismuth films,[15] plasma glycoproteins,[16] membrane bilayers,[17] and DNA molecules.[18]

Early history

Hand Hopewell mica
Hand carved from mica from the Hopewell tradition

Human use of mica dates back to prehistoric times. Mica was known to ancient Indian, Egyptian, Greek and Roman and Chinese civilizations, as well as the Aztec civilization of the New World.[19]

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 red (iron oxide, hematite, or red ochre) and black (manganese dioxide, pyrolusite), though black from juniper or pine carbons has also been discovered. White from kaolin or mica was used occasionally.

A few kilometers northeast of Mexico City stands the ancient site of Teotihuacan. The most striking structure of Teotihuacan is the towering Pyramid of the Sun. The pyramid contained considerable amounts of mica in layers up to 30 cm (12 in) thick.[20]

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 weathered 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, glittery micaceous finish over the entire object.[11]

Mica flakes (called abrak in Urdu and written as ابرک) are also used in Pakistan to embellish women's summer clothes, especially dupattas (long light-weight scarves, often colorful and matching the dress).[21][22] Thin mica flakes are added to a hot starch water solution, and the dupatta is dipped in this water mixture for 3–5 minutes. Then it is hung to air dry.

Mica powder

Throughout the ages, fine powders of mica have been used for various purposes, including decorations. Powdered mica glitter is used to decorate traditional water clay pots in India, Pakistan and Bangladesh; it is also used on traditional Pueblo pottery, though not restricted to use on water pots in this case. The gulal and abir (colored powders) used by North Indian Hindus during the festive season of Holi contain fine crystals of mica to create a sparkling effect. The majestic Padmanabhapuram Palace, 65 km (40 mi) from Trivandrum in India, has colored mica windows. Mica powder is also used as a decoration in traditional Japanese woodblock printmaking, as when applied to wet ink and allowed to dry it sparkles and reflects light.


Ayurveda, the Hindu system of ancient medicine prevalent in India, includes the purification and processing of mica in preparing Abhraka bhasma, which is employed in treating diseases of the respiratory and digestive tracts.[23][24]

Health impact

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

United States

The Occupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for mica exposure in the workplace as 20 mppcf over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (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 and health.[25]


Some lightweight aggregates, such as diatomite, perlite, and vermiculite, may be substituted for ground mica when used as filler. Ground synthetic fluorophlogopite,[26] a fluorine-rich mica, may replace natural ground mica for uses that require thermal and electrical properties of mica. Many materials can be substituted for mica in numerous electrical, electronic, and insulation uses. Substitutes include acrylate polymers, cellulose acetate, fiberglass, fishpaper, nylon, phenolics, polycarbonate, polyester, styrene, vinyl-PVC, and vulcanized fiber. Mica paper made from scrap mica can be substituted for sheet mica in electrical and insulation applications.[10]

See also

  • Cinnabar on Dolomite.jpg Minerals portal


  1. ^ "Mica" Archived 2015-01-16 at the Wayback Machine. Minerals Education Coalition.
  2. ^ "The Mica Group" Archived 2015-03-02 at the Wayback Machine. Rocks And Minerals 4 U.
  3. ^ "Mica" Archived 2015-03-17 at the Wayback Machine. mineralszone.com.
  4. ^ "Amethyst Galleries – THE MICA GROUP" Archived 2014-12-30 at the Wayback Machine. galleries.com.
  5. ^ Kirkpatrick, E. M., ed. (1983). Chambers 20th Century Dictionary. Schwarz, Davidson, Seaton, Simpson, Sherrard (New ed.). Edinburgh: W & R Chambers Ltd. p. 793. ISBN 0550102345.
  6. ^ W. A. Deer, R. A. Howie and J. Zussman (1966) An Introduction to the Rock Forming Minerals, Longman, ISBN 0-582-44210-9.
  7. ^ a b "Mineralogy: Phyllosilicates". Colgate University. 1997. Archived from the original on 19 September 2015. Retrieved 18 April 2016.
  8. ^ Rickwood, P. C. (1981). "The largest crystals" (PDF). American Mineralogist. 66: 885–907. Archived (PDF) from the original on 2013-08-25.
  9. ^ "The giant crystal project site". Archived from the original on 2009-06-04. Retrieved 2009-06-06.
  10. ^ a b Mica Archived 2011-10-30 at the Wayback Machine, USGS Mineral Commodity Summaries 2011
  11. ^ a b c d e f g h i j k Dolley, Thomas P. (2008) "Mica" Archived 2011-10-30 at the Wayback Machine in USGS 2008 Minerals Yearbook.
  12. ^ Isinglass curtains are referred to in the 1943 musical Oklahoma's song The Surrey with the Fringe on Top.
  13. ^ Wilke, Joanne (2007). Eight Women, Two Model Ts and the American West. University of Nebraska Press. ISBN 0803260199.
  14. ^ Eaton, P. and West, W. (2010) "Substrates for AFM", pp. 87–89 in Atomic Force Microscopy. Oxford University Press. ISBN 978-0-19-957045-4.
  15. ^ Weisenhorn, A. L. (1991). "Atomically resolved images of bismuth films on mica with an atomic force microscope". Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures. 9 (2): 1333. doi:10.1116/1.585190.
  16. ^ Marchant, R. E.; Lea, A. S.; Andrade, J. D.; Bockenstedt, P. (1992). "Interactions of von Willebrand factor on mica studied by atomic force microscopy" (PDF). Journal of Colloid and Interface Science. 148: 261. doi:10.1016/0021-9797(92)90135-9.
  17. ^ Singh, S; Keller, D. J. (1991). "Atomic force microscopy of supported planar membrane bilayers". Biophysical Journal. 60 (6): 1401–10. doi:10.1016/S0006-3495(91)82177-4. PMC 1260200. PMID 1777565.
  18. ^ Thundat, T; Allison, D. P.; Warmack, R. J.; Brown, G. M.; Jacobson, K. B.; Schrick, J. J.; Ferrell, T. L. (1992). "Atomic force microscopy of DNA on mica and chemically modified mica". Scanning microscopy. 6 (4): 911–8. PMID 1295085.
  19. ^ Haze, Xaviant (2016-11-21). Ancient Giants of the Americas: Suppressed Evidence and the Hidden History of a Lost Race. Red Wheel/Weiser. ISBN 9781632659323.
  20. ^ Fagan, Garrett G. (2006). Archaeological Fantasies: How Pseudoarchaeology Misrepresents the Past and Misleads the Public. New York: Routledge. p. 102. ISBN 0415305934.
  21. ^ Dehlvi, Sadia (October 14, 2007). "Tradition and modernity". Dawn.com. Archived from the original on October 20, 2013.
  22. ^ Ramzi, Shanaz (March 31, 2005). "Fashion through the ages". Dawn.com. Archived from the original on October 20, 2013.
  23. ^ "Abhraka Bhasma Preparation, Indications and Properties" Archived 2015-10-05 at Wikiwix "Ayurmedinfo.com".
  24. ^ "Abhraka Bhasma Properties and uses" Archived 2015-10-04 at the Wayback Machine "ayurtimes.com"
  25. ^ "CDC – NIOSH Pocket Guide to Chemical Hazards – Mica (containing less than 1% quartz)". www.cdc.gov. Archived from the original on 2015-12-08. Retrieved 2015-11-27.
  26. ^ "Fluorphlogopite - synthetic mica - Borosilicate and quartz glass, mica, sealing, level gauges, armature - Continental Trade". www.continentaltrade.com.pl. Archived from the original on 2018-02-12.


 This article incorporates public domain material from the United States Geological Survey document: "Mica".

External links


Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula K(Mg,Fe)3AlSi3O10(F,OH)2. More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous end-members include siderophyllite. Biotite was named by J.F.L. Hausmann in 1847 in honor of the French physicist Jean-Baptiste Biot, who performed early research into the many optical properties of mica.Biotite is a sheet silicate. Iron, magnesium, aluminium, silicon, oxygen, and hydrogen form sheets that are weakly bound together by potassium ions. It is sometimes called "iron mica" because it is more iron-rich than phlogopite. It is also sometimes called "black mica" as opposed to "white mica" (muscovite) – both form in the same rocks, and in some instances side-by-side.

Copșa Mică gas field

The Copşa Mică gas field is a natural gas field located in Copșa Mică, Sibiu County. It was discovered in 1915 and developed by and Romgaz. It began production in 1920 and produces natural gas and condensates. The total proven reserves of the Copşa Mică gas field are around 2.77 trillion cubic feet (80 km³), and production is slated to be around 3.7 million cubic feet/day (0.1×105m³) in 2010.

Dacian fortress of Pietroasa Mică

It was a Dacian fortified town.

Dacian fortress of Șeica Mică

It was a Dacian fortified town.

Dan Mica

Daniel Mica (born February 4, 1944) is an American politician who was a U.S. Representative from the state of Florida.

Deva, Romania

Deva (Romanian pronunciation: [ˈdeva] (listen); Hungarian: Déva, Hungarian pronunciation: [ˈdeːvɒ]; German: Diemrich, Schlossberg, Denburg; Latin: Sargetia; Turkish: Deve, Devevar) is a city in Romania, in the historical region of Transylvania, on the left bank of the Mureș River. It is the capital of Hunedoara County.


Făget (Romanian pronunciation: [fəˈdʒet]) is a town in Timiș County, Banat, western Romania, with a population of about 6,500.

Gudur, Nellore district

Gudur is a town in Nellore district of the Indian state of Andhra Pradesh. It is a municipality and the headquarters of Gudur mandal and Gudur revenue division.

John Mica

John Luigi Mica (born January 27, 1943) is an American businessman, consultant and Republican politician who represented Florida's 7th congressional district in the U.S. House of Representatives from 1993 to 2017. He was defeated by Democrat Stephanie Murphy in the November 8, 2016, general election while serving his 12th term in office.

MICA (institute)

MICA, formerly Mudra Institute of Communications, Ahmedabad, is a higher education institution for Strategic Marketing and Communication skills in India. Established in 1991, it is located on the outskirts of the western Indian city of Ahmedabad.

MICA (missile)

The MBDA MICA (Missile d’interception, de combat et d’autodéfense, “interception, combat and self-defence missile”) is an anti-air multi-target, all weather, fire-and-forget short and medium-range missile system. It is intended for use both by air platforms as individual missiles as well as ground units and ships, which can be equipped with the rapid fire MICA Vertical Launch System. It is fitted with a thrust vector control (TVC) system. It was developed from 1982 onward by Matra. The first trials occurred in 1991, and the missile was commissioned in 1996 to equip the Rafale and Mirage 2000. It is a replacement for both the Super 530, in the interception role, and the Magic II, in the dogfighting role.

On 11 June 2007, a MICA launched from a Rafale successfully demonstrated its over-the-shoulder capability by destroying a target behind the launch aircraft. The target was designated by another aircraft and coordinates were transmitted by Link 16.

Maryland Institute College of Art

The Maryland Institute College of Art (MICA) is a private art and design college in Baltimore, Maryland. It was founded in 1826 as the Maryland Institute for the Promotion of the Mechanic Arts, making it one of the oldest art colleges in the United States.

MICA is a member of the Association of Independent Colleges of Art and Design (AICAD), a consortium of 36 leading US art schools, as well as the National Association of Schools of Art and Design (NASAD). The college hosts pre-college, post-baccalaureate, continuing studies, Master of Fine Arts, and Bachelor of Fine Arts programs, as well as young peoples' studio art classes.

Metamorphic rock

Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock (protolith) is subjected to heat (temperatures greater than 150 to 200 °C) and pressure (100 megapascals (1,000 bar) or more), causing profound physical or chemical change. The protolith may be a sedimentary, igneous, or existing metamorphic rock.

Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. They are classified by texture and by chemical and mineral assemblage (metamorphic facies). They may be formed simply by being deep beneath the Earth's surface, subjected to high temperatures and the great pressure of the rock layers above it. They can form from tectonic processes such as continental collisions, which cause horizontal pressure, friction and distortion. They are also formed when rock is heated by the intrusion of hot molten rock called magma from the Earth's interior. The study of metamorphic rocks (now exposed at the Earth's surface following erosion and uplift) provides information about the temperatures and pressures that occur at great depths within the Earth's crust.

Some examples of metamorphic rocks are gneiss, slate, marble, schist, and quartzite.

Mica Peak

Mica Peak is the name of two separate mountain summits in the United States located approximately 5.49 miles (9 km) apart; one in Spokane County, Washington and the other in Kootenai County, Idaho. The two peaks are located along the same ridge, which separates the Spokane Valley and Rathdrum Prairie from the Palouse. The mountains have an elevation difference of only 31 ft (9.4 m) and are the southernmost peaks of the Selkirk Mountains.

Other summits located along the same ridge include the 4,045 ft (1,233 m) Round Mountain, the 4,924 ft (1,501 m) Cable Peak, the 4,852 ft (1,479 m) Shasta Butte, and the 4,377 ft (1,334 m) Blossom Mountain.

Mica Peak Air Force Station

Mica Peak Air Force Station (ADC ID: SM-151, NORAD ID: Z-141) is a closed United States Air Force General Surveillance Radar station. It is located 6.3 miles (10.1 km) east-northeast of Mica, Washington. It was closed in 1975 by the Air Force, and turned over to the Federal Aviation Administration (FAA).

Today the site is part of the Joint Surveillance System (JSS), designated by NORAD as Western Air Defense Sector (WADS) Ground Equipment Facility J-79.


Muscovite (also known as common mica, isinglass, or potash mica) is a hydrated phyllosilicate mineral of aluminium and potassium with formula KAl2(AlSi3O10)(FOH)2, or (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, India.

Muscovite has a Mohs hardness of 2–2.25 parallel to the [001] face, 4 perpendicular to the [001] and a specific gravity of 2.76–3. It can be colorless or tinted through grays, browns, greens, yellows, or (rarely) violet or red, and can be transparent or translucent. It is anisotropic and has high birefringence. Its crystal system is monoclinic. The green, chromium-rich variety is called fuchsite; mariposite is also a chromium-rich type of muscovite.

Muscovite is the most common mica, found in granites, pegmatites, gneisses, and schists, and as a contact metamorphic rock or as a secondary mineral resulting from the alteration of topaz, feldspar, kyanite, etc. In pegmatites, it is often found in immense sheets that are commercially valuable. Muscovite is in demand for the manufacture of fireproofing and insulating materials and to some extent as a lubricant.

The name muscovite comes from Muscovy-glass, a name given to the mineral in Elizabethan England due to its use in medieval Russia as a cheaper alternative to glass in windows. This usage became widely known in England during the sixteenth century with its first mention appearing in letters by George Turberville, the secretary of England's ambassador to the Russian tsar Ivan the Terrible, in 1568.


Petroșani (Romanian pronunciation: [petroˈʃanʲ]; German: Petroschen; Hungarian: Petrozsény) is a city in Hunedoara County, Transylvania, Romania, with a population of 34,331 (2011). The city has been associated with mining since the 19th century.


Schist (pronounced SHIST) is a medium-grade metamorphic rock. Schist has medium to large, flat, sheet-like grains in a preferred orientation (nearby grains are roughly parallel). It is defined by having more than 50% platy and elongated minerals (such as micas or talc), often finely interleaved with quartz and feldspar. These lamellar (flat, planar) minerals include micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is produced. Schist is often garnetiferous. Schist forms at a higher temperature and has larger grains than phyllite. Geological foliation (metamorphic arrangement in layers) with medium to large grained flakes in a preferred sheetlike orientation is called schistosity.The names of various schists are derived from their mineral constituents. For example, schists primarily composed of biotite and muscovite are called mica schists. Most schists are mica schists, but graphite and chlorite schists are also common. Schists are also named for their prominent or perhaps unusual mineral constituents, as in the case of garnet schist, tourmaline schist, and glaucophane schist.

The individual mineral grains in schist, drawn out into flaky scales by heat and pressure, can be seen with the naked eye. Schist is characteristically foliated, meaning that the individual mineral grains split off easily into flakes or slabs. The word schist is derived ultimately from the Greek word σχίζειν (schízein) meaning "to split", which is a reference to the ease with which schists can be split along the plane in which the platy minerals lie.

Most schists are derived from clays and muds that have passed through a series of metamorphic processes involving the production of shales, slates and phyllites as intermediate steps. Certain schists are derived from fine-grained igneous rocks such as basalts and tuffs.

Târnava River

The Târnava (fully Romanian: Râul Târnava, Hungarian: Küküllő; German: Kokel; Turkish: Kokul or Kokulu) is a river in Romania. It is formed by the confluence of the Târnava Mare and Târnava Mică in the town of Blaj. The Târnava flows into the Mureș after 23 km, near the town of Teiuş. Tributaries of the Târnava, besides its two source rivers Târnava Mare and Târnava Mică, are the Tiur, Izvorul Iezerului and Secaș from the left and the Șoimuș from the right. Its drainage basin covers an area of 6,253 km2 (2,414 sq mi).

Common minerals
Pyrophyllite series
Smectites and vermiculite family

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