The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. For the Artificial intelligence Androids of the 1990s Science fiction series Space Above and Beyond, see Silicate (AI A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Cleavage, in Mineralogy, is the tendency of crystalline materials to split along definite planes creating smooth surfaces of which there are several named types All are monoclinic with a tendency towards pseudo-hexagonal crystals and are similar in chemical composition. In Crystallography, the monoclinic Crystal system is one of the 7 lattice Point groups A crystal system is described by three vectors. In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating The highly perfect cleavage, which is the most prominent characteristic of mica, is explained by the hexagonal sheet-like arrangement of its atoms. Regular hexagon The internal Angles of a regular hexagon (one where all sides and all angles are equal are all 120 ° and the hexagon has 720 degrees History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny

The word "mica" is thought to be derived from the Latin word micare, to glitter, in reference to the brilliant appearance of this mineral (especially when in small scales). Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Mica has a lamellar form with a shiny luster. A lamella is a Gill -shaped structure fine sheets of material held adjacent one another with fluid in-between-(or simply 'welded'-plates

Contents 1 Mica classification 1.1 Tri-octahedral micas 1.2 Interlayer deficient micas 2 Occurrence 3 Properties and uses 4 Role in primitive life 5 Mica in ancient times 6 References 7 See also

Mica classification

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

X₂Y_4-6Z₈O₂₀(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 the micas can be classed as di-octahedral (Y = 4) and tri-octahedral (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.

Tri-octahedral micas

Common micas:

• Phlogopite
• Biotite
• Zinnwaldite
• Lepidolite

Brittle micas:

• Clintonite

Interlayer deficient micas

Very fine-grained micas with typically more variation in ion and water content are informally termed clay micas. Phlogopite is a yellow greenish or reddish-brown member of the Mica family of phyllosilicates. Biotite is a common phyllosilicate Mineral within the Mica group with the approximate chemical formula K(Mg Fe3AlSi3O10(F Zinnwaldite, K[[lithium Li]] Fe[[aluminum Al]](Al Si 3 O 10(O H, F)2 is a potassium lithium iron Lepidolite (KLi2Al(AlSi3O10(FOH2 is a lilac or rose-violet colored phyllosilicate Mineral of the Mica group Clintonite is a Calcium Magnesium Aluminium phyllosilicate mineral 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

The British Geological Survery reports that as of 2005, India had the largest deposits of mica in world. Illite is a non-expanding Clay -sized micaceous mineral Illite is a phyllosilicate or layered alumino-silicate Phengite is a series name for dioctahedral Micas of composition K(AlMg2(OH2(SiAl4O10 similar to Muscovite but with addition China was the top producer of mica with almost a third of the global share, closely followed by the USA, South Korea and Canada. Large Deposits of Sheet Mica were mined in New England from the 19th Century to the 1960's. Large mines existed in CT, NH and Maine.

Mica is widely distributed and occurs in igneous, metamorphic and sedimentary regimes. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) Large crystals of mica used for various applications are typically mined from granitic pegmatites. Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. Pegmatite is a very coarse-grained Igneous rock that has a grain size of 20 mm or more such rocks are referred to as pegmatitic.

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 during the early 1800s.

Scrap and flake mica is produced all over the world. 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. The schists form a group of medium-grade Metamorphic rocks chiefly notable for the preponderance of lamellar Minerals such as Micas chlorite 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 pegmatite deposits.

Properties and uses

Mica has a high dielectric strength and excellent chemical stability, making it a favoured material for manufacturing capacitors for radio frequency applications. In Physics, the term dielectric strength has the following meanings Of an insulating material the maximum electric Field strength that it can withstand A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors It has also been used as an insulator in high voltage electrical equipment. An insulator, also called a Dielectric, is a material that resists the flow of Electric current. It is also birefringent and is commonly used to make quarter and half wave plates. Birefringence, or double refraction, is the decomposition of a ray of Light into two rays (the ordinary ray and the extraordinary ray A wave plate or retarder 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. In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature A stove is an enclosed heated space The term is commonly taken to mean an enclosed space in which fuel is burned to provide heating either to heat the space in which the stove is situated A kerosene heater, also known as a paraffin heater, is a portable unvented Kerosene -fueled space-heating device 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. A cable is one or more Wires or Optical fibers bound together typically in a common protective jacket or sheath A fire-resistance rating typically means the duration for which a Passive fire protection System can withstand a standard fire resistance test. Circuit integrity refers to the operability of electrical circuits during a Fire. 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 applications such as emergency lighting. The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across

Illites or clay micas have a low cation exchange capacity for 2:1 clays. In Soil science, cation exchange capacity (CEC is the capacity of a Soil for Ion exchange of positively charged ions between the soil and the K+ ions between layers of mica prevent swelling by blocking water molecules.

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 inclusions that give a shimmering or glistening effect

Pressed Mica sheets are often used in place of glass in greenhouses. A greenhouse (also called a glasshouse or hothouse) is a building where plants are cultivated

Muscovite mica is the most common substrate for sample preparation for the atomic force microscope. Muscovite (also known as Common Mica, Isinglass, or Potash mica) is a phyllosilicate Mineral of Aluminium The atomic force microscope (AFM or scanning force microscope (SFM is a very high-resolution type of scanning probe microscope, with demonstrated resolution of fractions

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. The shimmer from mica is also used in makeup, as it gives a translucent "glow" to the skin or helps to mask imperfections.

Mica sheets are used to provide structure for heating wire (like Kanthal, Nichrome, etc. Kanthal is an Alloy of mainly Iron and Chromium (20–30 % Aluminium (4–75 % Nichrome is a brand name for a nickel-chromium resistance wire a non-magnetic Alloy of Nickel and Chromium. . ) in heating elements and can withstand up to 900 °C. A heating element converts Electricity into Heat through the process of Joule heating. ^{[2] [3] [4]}

Another use of Mica is in the production of ultraflat thin film surfaces (e. g. gold surfaces) using mica as substrate. Although the deposited film surface is still rough due to deposition kinetics, the back side of the film at mica-film interface provides ultraflatness, when the film is removed from the substrate.

Mica slices are used in electronics to provide electric insulation between a heat generating component and the heat sink used to cool it^[5] . In the manufacturing of electronic devices a mica insulator is a Die-cut punched insulator of natural or "block" Mica splittings The same word is sometimes used by technicians to designate a synthetised gum (usually blue or grey) which is used for the same purpose, but which does not actually consist of silicate mineral (language abuse).

Role in primitive life

Helen Hansma, a research scientist affiliated with the University of California, has proposed that the unique properties of Mica enabled the formation of life in the oceans of the distant past. The University of California ( UC) is a Public university system in the state of California. ^{[6] [7]} In atomic force microscopy, biological samples are placed on mica because it is atomically flat. Even bare DNA molecules may be seen as small ridges. Inspecting mica under the microscope, bits of algae and other organic materials suggested to her the possibility early life molecules could have evolved within mica sheets in a communal fashion eons before the evolution of cell membranes or lipid vesicles. Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble A vesicle is a small bubble of liquid within a cell A more formal definition in Cell biology, would be that a vesicle is a relatively small intracellular membrane-enclosed Mica might have provided a secure place with time and space and protection from the open ocean. Further research might provide additional predictions about energy and entropy for life. Mica is old rock, some of earliest evidence for life's most primitive cells is in Akilia Island, Greenland, where biotite, a common mica, is also found. Akilia Island is in West Greenland, about 22 kilometers south of Nuuk (Godthåb at. Greenland (Kalaallit Nunaat meaning "Land of the Greenlanders" Grønland is a self-governing Danish Province located between the Biotite is a common phyllosilicate Mineral within the Mica group with the approximate chemical formula K(Mg Fe3AlSi3O10(F Potassium ions, which hold the sheets of mica together, are is also required by cells. Potassium (pəˈtæsiəm is a Chemical element. It has the symbol K (kalium from qalīy Atomic number 19 and Atomic mass 39 Primordial soup with amino acids and simple building blocks of life might have seeped between the water-loving mica sheets. In the Natural sciences, Abiogenesis, or origin of life, is the study of how Life on Earth emerged from Inanimate Organic In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this The large planer area between sheets might have facilitated the building of long chain molecules. Negative spaces holding the potassium ions on mica are 0. 5 nm apart, as are the single stranded DNA molecules (letters of genetic code), as well as amino acids in proteins. Clay also provides spacing that might encourage this process, but the planer area might better encourage the process. Expansion and contraction caused by temperature changes and ocean currents might provide mechanical energy to help rearrange the molecules and trigger the formation of chemical bonds.

Mica in ancient times

Human use of mica dates back to pre-historic times. The Hopewell tradition (also incorrectly called the "Hopewell culture" is the term used to describe common aspects of the Native American culture that flourished along Stone Age Paleolithic See also Paleolithic, Recent African Origin, Early Homo sapiens, Early human migrations "Paleolithic" Mica was known to ancient Egyptian, Greek and Roman civilizations, Chinese civilization, as well as the Aztec civilization of the New World. Ancient Egypt was an Ancient Civilization in eastern North Africa, concentrated along the lower reaches of the Nile River in what is now The term ancient Greece refers to the period of Greek history lasting from the Greek Dark Ages ca Ancient Rome was a Civilization that grew out of a small agricultural community founded on the Italian Peninsula as early as the 10th century BC Chinese civilization originated in various city-states along the Yellow River ( valley in the Neolithic era Aztec is a term used to refer to certain ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl language and who achieved political The New World is one of the names used for the non-Eurasian/non-African parts of the Earth specifically the Americas and Australia.

The earliest use of mica has been found in cave paintings created during the Upper Paleolithic period (40,000 BC to 10,000 BC). Cave paintings are Paintings on Cave walls and ceilings and the term is used especially for those dating to Prehistoric times The term Paleolithic (or Palaeolithic) (from Greek παλαιός palaios, " Old " and λίθος Lithos, "stone" The first colours were red, iron oxide (hematite, a form of red ochre) and black (manganese dioxide), though black from juniper or pine carbons has also been discovered. White from kaolin or mica was used occasionally.

A few kilometeres northeast of Mexico City stands the ancient site of Teotihuacan. Mexico City (in Spanish: Ciudad de México, México DF, México or simply Méjico) is the Capital city of Mexico Teotihuacan is an enormous archaeological site in the Basin of Mexico, containing some of the largest pyramidal structures built in the Pre-Columbian Americas The most striking visual and striking structure of Teotihuacan is the towering pyramid of the sun. A pyramid is a Building where the upper surfaces are triangular and converge on one point The pyramid contained considerable amounts of locally mined mica in layers up to 30cm thick. ^[8]

Throughout 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. A Hindu ( Devanagari: हिन्दू is an adherent of the philosophies and scriptures of Hinduism, a set of religious, Philosophical Holi ( or language|Bhojpuri]] also called the Festival of Colours, is a popular Hindu spring Festival observed in India, The majestic Padmanabhapuram palace, 65 km from Trivandrum in India, has coloured mica windows. Padamanabhapuram Palace complex is located in at Padmanabhapuram Fort close to the town of Thuckalay in Kanyakumari District, Tamilnadu. Thiruvananthapuram ( Malayalam: തിരുവനന്തപുരം Tiruvanantapuraṁ) also known as Trivandrum, is the capital of the

References

• Mineral Galleries data
• Mindat

See also

• Mica insulator

In the manufacturing of electronic devices a mica insulator is a Die-cut punched insulator of natural or "block" Mica splittings

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