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Encyclopedia > Mica
Rock with mica
Rock with mica
Mica sheet
Mica sheet
Mica flakes
Mica flakes

The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic with a tendency towards pseudo-hexagonal crystals and are similar in chemical composition. The highly perfect cleavage, which is the most prominent characteristic of mica, is explained by the hexagonal sheet-like arrangement of its atoms. Download high resolution version (500x802, 82 KB)I picked up this rock at an abandoned mica quarry near Alstead, NH, in July 2004 File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Download high resolution version (500x802, 82 KB)I picked up this rock at an abandoned mica quarry near Alstead, NH, in July 2004 File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Mica sheet Source: US Government File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Mica sheet Source: US Government File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... I picked up these flakes of mica at an abandoned mica quarry near Alstead, NH, in July of 2004. ... I picked up these flakes of mica at an abandoned mica quarry near Alstead, NH, in July of 2004. ... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... Minerals are natural compounds formed through geological processes. ... Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types: Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes. ... In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. ... Quartz crystal Synthetic bismuth crystal Insulin crystals Gallium, a metal that easily forms large single crystals A huge monocrystal of potassium dihydrogen phosphate grown from solution by Saint-Gobain for the megajoule laser of CEA. In chemistry and mineralogy, a crystal is a solid in which the constituent atoms, molecules... Properties In chemistry and physics, an atom (Greek ἄτομος or átomos meaning indivisible) is the smallest particle still characterizing a chemical element. ...

The word "mica" is thought to be derived from the Latin word micare, meaning to shine, in reference to the brilliant appearance of this mineral (especially when in small scales). Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ...


Mica classification

Chemically micas can be given the general formula:[1]

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 the micas can be classed as di-octahedral (Y = 4) and tri-octahedral (Y = 6). Also 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.

¡mica sheet

Di-octahedral micas

Common micas:

Brittle micas: Muscovite layer Muscovite, also known as potash mica, is a phyllosilicate mineral of aluminium and potassium with formula: KAl2(AlSi3O10)(F,OH)2. ... Paragonite, also known as Natron-Glimmer, Paragonit or Paragonita, is a mineral, related to muscovite. ... A sample of glauconite Glauconite is a phyllosilicate (mica group) mineral of formula: (K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2. ...

Margarite is a calcium rich member of the mica group of the phyllosilicates with formula: CaAl2(Al2Si2)O10(OH)2. ...

Tri-octahedral micas

Common micas:

Brittle micas Phlogopite is a yellow, greenish or reddish brown member of the mica family of phyllosilicates. ... A Biotite slice Biotite is a common phyllosilicate mineral that contains potassium, magnesium, iron and aluminium. ... Zinnwaldite, KLiFeAl(AlSi3)O10(OH,F)2, is a potassium lithium iron aluminium silicate hydroxide fluoride silicate mineral in the mica group. ... Crystal of lepidolite, Brazil Lepidolite (KLi2Al(Al,Si)3O10(F,OH)2) is a lilac or rose-violet colored phyllosilicate mineral of the mica group that is a secondary source of lithium. ...

Clintonite is a group of micaceous minerals known as the brittle micas. ...

Interlayer deficient micas

Very fine grained micas with typically more variation in ion and water content are informally termed clay micas and 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.

Structure of Illite mica - USGS. Illite is a non-expanding, clay-sized, micaceous mineral. ...


Micas are widely distributed and occur in igneous, metamorphic and sedimentary regimes. Large crystals of mica used for various applications are typically mined from granitic pegmatites. Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Metamorphic rock is the result of the transformation of a pre-existing rock type, the protolith, in a process called metamorphism, which means change in form, derived from the Greek words meta, change, and morphe, form. The protolith is subjected to extreme heat (>150 degrees Celsius) and pressure causing profound... Two types of sedimentary rock: limey shale overlaid by limestone. ... Granite is a common and widely-occurring group of intrusive felsic igneous rocks that form at great depths and pressures under continents. ... This article or section does not cite its references or sources. ...

Until the 19th century, large crystals of mica were quite rare and expensive as a result of the limited supply in Europe. However, its price dramatically dropped when large reserves were found and mined in Africa and South America after the early 19th century.

Scrap and flake mica is produced all over the world. The flake mica comes from several sources: the metamorphic rock called schist as a by-product of processing feldspar and kaolin resources, from placer deposits, and from pegmatites. Major producers of flake mica are Canada, India, Finland, and Japan. Sheet mica is considerably less abundant than flake and scrap mica. Sheet mica is occasionally recovered from mining scrap and flake mica. The most important sources of sheet mica are the pegmatite deposits. Major sheet mica mining countries are India, Belgium, Germany and China. Schist The schists form a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. ...

Properties and uses

Mica has a high dielectric strength and excellent chemical stability, making it a favored material for manufacturing capacitors for radio frequency applications. It has also been used as an insulator in high voltage electrical equipment. It is also birefringent and is commonly used to make quarter and half wave plates. In physics, the term dielectric strength has the following meanings: Of an insulating material, the maximum electric field strength that it can withstand intrinsically without breaking down, , without experiencing failure of its insulating properties. ... Various types of capacitors A capacitor is a device that stores energy in the electric field created between a pair of conductors on which equal but opposite electric charges have been placed. ... This article or section is in need of attention from an expert on the subject. ... A calcite crystal laid upon a paper with some letters showing the double refraction Birefringence, or double refraction, is the decomposition of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals, depending on... A wave plate is an optical device that alters the polarization state of a light wave travelling through it. ...

Because mica is resistant to heat it is used instead of glass in windows for stoves and kerosene heaters. It is also used to separate electrical conductors in cables that are designed to have a fire-resistance rating in order to provide circuit integrity. The idea is to keep the metal conductors from fusing in order to prevent a short-circuit so that the cables remain operational during a fire, which can be important for such things as emergency lighting to facilitate emergency evacuations in a building or ship during an accidental fire. In physics, heat, symbolized by Q, is defined as transfer of thermal energy [1] Generally, heat is a form of energy transfer associated with the different motions of atoms, molecules and other particles that comprise matter when it is hot and when it is cold. ... A stove is a heat-producing device. ... A kerosene heater is a portable unvented kerosene fueled space heating device. ... 6 or 15cm outside diameter, oil-cooled cables, traversing the Grand Coulee Dam throughout. ... International time/temperature curves used to run commercial furnaces for testing the Fire-resistance rating of passive fire protection systems, such as firestops, fire doors, wall and floor assemblies, etc. ... Method 1: fire-resistant cables: PVC-sheathed MICC cable. ... Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily loses electrons to form positive ions (cations) and has metallic bonds between metal atoms. ... Emergency evacuation is the movement of persons from a dangerous place due to the threat or occurrence of a disastrous event. ... For other uses, see Building (disambiguation). ... Italian Full rigged ship Amerigo Vespucci in New York Harbor, 1976 A ship is a large watercraft capable of deep water navigation. ...

Illites or clay micas have a low cation exchange capacity for 2:1 clays. K+ ions between layers of mica prevent swelling by blocking water molecules. This article does not cite its references or sources. ...

Aventurine is a variety of quartz with mica inclusions used as a gemstone. Aventurine is a form of quartz, characterised by its translucency and the presence of platy mineral occlusions that give a shimmering or glistening effect termed aventurescence. ...

Pressed Mica sheets are often used in place of glass in greenhouses. A greenhouse in Saint Paul, Minnesota. ...

Muscovite mica is the most common substrate for sample preparation for the Atomic force microscope. The atomic force microscope (AFM) is a very high-resolution type of scanning probe microscope, with demonstrated resolution of fractions of an Angstrom, more than 1000 times better than the optical diffraction limit. ...

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 in ancient times

Hand carved from mica from the Hopewell culture
Hand carved from mica from the Hopewell culture

Human use of mica dates back to pre-historic times, and mica was known to ancient Egyptian, Greek and Roman civilizations, Chinese civilization, as well as the Aztec civilization of the New World. Image File history File links Hand_Hopewell_mica. ... Image File history File links Hand_Hopewell_mica. ... Hopewell culture is the term used to describe common aspects of the Native American culture that flourish along rivers in the northeastern and midwestern United States from 200 BC to 400 A.D. At its greatest extent, Hopewell culture stretched from western New York to Missouri and from Wisconsin to... Prehistory (Greek words προ = before and ιστορία = history) is the period of human history prior to the advent of writing (which marks the beginning of recorded history). ... Area under Roman control  Roman Republic  Roman Empire  Western Empire  Eastern Empire Ancient Rome was a civilization that grew from a city-state founded on the Italian Peninsula circa the 9th century BC to a massive empire straddling the Mediterranean Sea. ... The Aztecs is a collective term used for all of the Pre-Columbian Mesoamerican peoples under the control of the Mexica, founders of Tenochtitlan, and their two principal allies, who built an extensive empire in the late Postclassic period in the 14th, 15th and 16th centuries in Central Mexico. ... Carte dAmérique, Guillaume Delisle, c. ...

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 colors were red, iron oxide (hematite, a form of red ochre) and black (manganese dioxide), though black from bridget or pine carbons has also been discovered. White from kaolin or mica was used occasionally. Cave, or rock, paintings are paintings painted on cave or rock walls and ceilings, usually dating to pre_historic times. ... The Paleolithic or Palaeolithic (Greek παλαιός paleos=old and λίθος lithos=stone or the Old Stone Age) was the first period in the development of human technology of the Stone Age. ...

A few kilometeres northeast of Mexico City stands the ancient site of Teotihuacan. The most striking visual and striking structure of Teotihuacan is the towering pyramid of the sun. The pyramid contained considerable locally mined mica in layers up to one-foot thick.[2] Nickname: Ciudad de los Palacios Location of Mexico City in central Mexico Coordinates: Country Mexico Federal entity Federal District Boroughs The 16 delegaciones Founded (as Tenochtitlan) c. ... Teotihuacan was the largest Pre-Columbian known city in the Americas, and the name Teotihuacan is used to refer to the civilization this city dominated, which at its greatest extent included most of Mesoamerica. ... A pyramid is any three-dimensional structure where the upper surfaces are triangular and converge on one point. ...

Through out the ages, fine powders of mica have been used for various purposes, including decorative purposes. The coloured Gulal and Abeer used by Hindus of north India during holi festival contain fine small crystals of mica. The majestic Padmanabhapuram palace, Padmanabhapuram, 65 km from Trivandrum, India, has coloured mica windows. This article is about the Hindu religion; for other meanings of the word, see Hindu (disambiguation). ... Celebration of Holi Holi (Hindi: होली) or Phagwah (Bhojpuri) is a popular, Hindu spring festival, observed in India, also called the Festival of Colours. ... Padamanabhapuram Palace complex is located in a small village Padmanabhapuram, around 65 km from Trivandrum, Kerala, India, en route to Kanyakumari, Tamilnadu. ... Padmanabhapuram was the old capital of the princely state Travancore in India. ... Indian Coffee House Thiruvananthapuram or Thiruvanathapuram (formerly known as Trivandrum) is the capital (population - 889,191 (2001)) of the state of Kerala, India. ...

The medieval Chinese mechanical engineer, horologist, pharmacologist, and statesman Su Song (1020-1101 AD) of the Song Dynasty outlined in his book Ben Cao Tu Jing the medicinal properties and uses of the then every known type of mica (which was 8 in all, refer to article on mineralogy). For the Technical Symposium of NITK Surathkal Engineer , see Engineer (Technical Fest). ... Horology is the science and study of timekeeping devices. ... Pharmacology (in Greek: pharmacon is drug, and logos is science) is the study of how chemical substances interfere with living systems. ... Su Song 蘇頌 (1020 – 1101), style Zirong 子容, was a Chinese engineer. ... Events Hospice built in Jerusalem by Knights Hospitaller City of Saint-Germain-en-Laye founded Third Italian campaign of Henry II of Germany Canute the Great codifies the laws of England Births Harold II of England (approximate) Empress Agnes of Poitou, regent of the Holy Roman Empire (d. ... Events A second wave of crusaders arrives in the newly established Kingdom of Jerusalem, after being heavily defeated by Kilij Arslan I at Heraclia. ... Northern Song in 1111 AD Capital Kaifeng (960–1127) Linan (1127–1279) Language(s) Middle Chinese Religion Buddhism, Taoism, Confucianism Government Monarchy History  - Zhao Kuangyin taking over the throne of the Later Zhou Dynasty 960  - Battle of Yamen; the end of Song rule 1279 Population  - Peak est. ... Mineralogy is an earth science that involves the chemistry, crystal structure, and physical (including optical) properties of minerals. ...


  1. ^ Deer, W. A., R. A. Howie and J. Zussman (1966) An Introduction to the Rock Forming Minerals, Longman, ISBN 0-582-44210-9
  2. ^ Garrett G. Fagan, ed., Archaeological Fantasies: How Pseudoarchaeology Misrepresents the Past and Misleads the Public, p. 102, ISBN 0415305934
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  Results from FactBites:
Mica - LoveToKnow 1911 (1897 words)
When a cleavage flake of mica is struck a sharp blow with a blunt needle-point a six-rayed star of cracks or "percussion figure" is developed: the rays intersect at angles of approximately 60┬░, and the pair most prominently developed are parallel to the plane of symmetry of the crystal.
Mica occurs as a primary and essential constituent of igneous rocks of almost all kinds; it is also a common product of alteration of many mineral silicates, both by weathering and by contactand dynamo-metamorphic processes.
In dressing mica the "books" are split along the cleavage into sheets of the required thickness, and the sheets trimmed into rectangles with a sharp knife, shears or guillotine, stained and damaged portions being rejected.
  More results at FactBites »



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