Mica minerals are divided into two subclasses, and there are nine kinds of minerals. Muscovite subfamily, including paragonite, muscovite, vanadic mica and glauconite; The phlogopite-biotite subfamily includes phlogopite-biotite, zinc triple mica, zinc mica, manganese lepidolite, copper uranium mica and lepidolite.
Mica is the floorboard of hydrous aluminosilicate minerals with layered structure, containing lithium, sodium, potassium, magnesium, aluminum, zinc, iron and vanadium. It mainly includes muscovite, biotite, phlogopite and lepidolite. The mica mineral raw materials used in industry are flake mica, crushed mica and sericite among muscovite and phlogopite, of which muscovite is the most widely used, followed by phlogopite. Because mica has high electrical insulation, good transparency, excellent stripability, high chemical stability and good reducibility, and can maintain the above excellent physical and chemical properties at high temperature, it is mainly used as a very important insulating material in electronic, motor, telecommunications, electrical appliances, aviation, transportation, instrumentation, metallurgy, building materials, light industry and other industrial sectors, as well as national defense and cutting-edge industries. Since 1970s, mica used in insulating supporting materials and dielectric materials of capacitors and motors has been replaced by mica paper made of broken mica, and most communication tubes have been replaced by semiconductor integrated circuits, which has fundamentally changed the consumption structure, thus greatly reducing the demand for flaky mica and increasing the demand for broken mica. With the development of science and technology, the application of mica minerals in building materials, geological exploration, lubrication, coatings, food and cosmetics has been expanding in recent years, and the raw materials of broken mica and sericite minerals will have broad application prospects.
Chemical composition: the chemical formula of muscovite is kal2 (alsi3o10) (oh) 2; The chemical formula of muscovite is (Fe2+, MG) (Fe3+, Al3+) (ALS i7O20) (OH) 4; The chemical formula of sericite is kal2 (Si, Al) 4o 10 (OH, F) 2; The chemical formula of phlogopite is KMg3(AlSi3O 10)(F, OH)2 mica, which is an aluminosilicate mineral with continuous layered silicon-oxygen tetrahedron structure and extremely complete cleavage. Can be peeled into elastic sheets, soft and elastic, transparent and colorless, thick and translucent with gray, brown, light green and rose red, with glass to spun silk or pearl luster and hardness of 2.5 ~.
muscovite
Chemical constituents of muscovite: KAl2[Si3AlO 10](OH, F)2. The ideal composition is that octahedral flake contains al, and it can also be replaced by Fe 3+, Mg, Fe 2+ or even Mn, Cr, V, etc. Muscovite has a highly complete cleavage and a pale white color. The sheet is elastic.
Muscovite is one of the widely distributed rock-forming minerals, which are found in all three rock types. The argillaceous rocks can form sericite in the process of low-level regional metamorphism, and become muscovite when the metamorphic degree is slightly higher. A large number of muscovites were formed in the late crystallization stage and pegmatization stage of acid magma. It can also be formed in the process of alteration from high temperature to medium and low temperature. The so-called greisenization is a kind of high temperature alteration, which can form a large number of muscovite. The so-called sericitization is a kind of medium-low temperature alteration, which can form a large number of sericite. Muscovite is weathered and broken into very fine scales, which can be either debris in clastic sediments or one of the mineral components of argillaceous rocks.
Muscovite rhombohedral crystal, usually plate-shaped or sheet-shaped, forms a pseudo-hexagon or diamond shape on the outside. The cylinder has obvious horizontal stripes. Twins are common, and contact twins or triplets are generated according to mica law.
Phlogopite (phlogopite)
The chemical formula of phlogopite is KMg3[AlSi3O 10][F, OH]2. Because its physical and chemical properties are different from muscovite, it has many special functions and has been applied in many important fields. In industry, it is mainly used as an insulating material for electrical equipment and electrical equipment because of its high electrical insulation and heat resistance, as well as strong acid resistance, alkali resistance, pressure resistance and peeling performance. Phlogopite is usually yellow, dark brown or black, glassy, and its cleavage surface is pearl or semi-metallic luster. It can be corroded by concentrated sulfuric acid, decomposed in concentrated sulfuric acid and produced milky white solution at the same time. Sodium, calcium and barium replaced potassium in the chemical composition. Substitutes for magnesium are titanium, iron, manganese and chromium; Fluorine replaces OH, and the varieties of phlogopite are manganese mica, titanium mica, chromium phlogopite, fluorine phlogopite and so on. Characteristic properties produce characteristic uses.
black mica
The chemical composition of biotite: K (Mg, Fe2+) 3 (Al, Fe3+) Si3O 10 (OH, F) 2, which is widely replaced by isomorphism, so the chemical composition of biotite produced in different rocks is quite different. Generally speaking, biotite in acidic and alkaline magmatic rocks has the characteristics of high FeO and low MgO, and biotite in ultrabasic rocks has the characteristics of high MgO and low FeO. In biotite in alkaline pegmatite, MgO content is low, while Fe2O3 content is relatively high.
The crystal morphology of biotite is the same as that of phlogopite. The color is black, dark brown, sometimes with light red, light green or other tones. Those with high titanium content are reddish brown and those with high iron content are green. Transparent to opaque. Glass luster, black is semi-metallic luster. Hardness 2-3, specific gravity 3.02-3. 12. Under the action of heated aqueous solution, biotite can be transformed into chlorite, muscovite and sericite. Biotite has high iron content and poor thermal insulation performance, which is far less than muscovite. Mica flakes are often used as fillers in building materials. The biotite with large particle size is easy to identify according to its flaky, deep and elastic color, perfect cleavage and micro-magnetism after heating. In plutonic and hypabyssal rocks, especially in acidic or alkaline rocks, biotite is mostly contained.
Sericite (sericite)
Sericite is a natural fine-grained muscovite, which belongs to a subspecies of muscovite and is a silicate with layered structure. Its structure consists of two silicon-oxygen tetrahedrons sandwiched between an aluminum-oxygen octahedron. {00 1} cleavage is complete, and it can be split into extremely thin slices, and the thickness of the slices can reach below 1u (theoretically, it can be cut into 0.00 1u), with a large diameter-thickness ratio; Compared with muscovite, it has the characteristics of small natural particle size, easy processing and superfine. The chemical formula of sericite crystal is: k0.5- 1 (Al, Fe, Mg) 2 (Sial) 4o 10 (OH) 2? NH _ 2O, general chemical composition: SiO _ 2 43. 13 ~ 49.04%, Al _ 2O _ 3 27.93 ~ 37.44%, K2O+Na _ 2O _ 9 ~1%,H _ 2O _.
Sericite belongs to monoclinic crystal, which is scaly and has sericite luster (muscovite has glass luster), and pure blocks are gray, purple rose and white. , and the diameter-thickness ratio is more than: 80, the specific gravity is 2.6~2.7, the hardness is 2~3, and it has elasticity, flexibility and good wear resistance and abrasion resistance; Heat-resistant and insulating, insoluble in acid-base solution, and stable in chemical properties. Test data: elastic modulus 1505~2 134MPa, heat resistance of 500~600oC, thermal conductivity of 0.419 ~ 0.670 w (m.k)-1,electrical insulation of 200kv/mm and radiation resistance of 5.
In addition, sericite is similar to kaolin in chemical composition, structure and structure, and has some characteristics of clay minerals, that is, it has good dispersion and suspension in water media and organic solvents, and its particles are fine, white and sticky. Therefore, sericite has many characteristics of mica minerals and clay minerals.
Sodium amphibole (sodium amphibole)
Sodium zeolite is a hydrated sodium aluminosilicate and a mica. It is often associated with muscovite and can be distinguished from it by its physical properties. The difference between these two mica lies in their chemical composition. In paragonite, sodium ions occupy the structural position of potassium in muscovite.
Lepidolite (lepidolite, lavender, crystal), lavender, crystal
The chemical composition of lepidolite is k (li, Al) 2.5-3 [Si 3.5-3Al0.5-1O10] (OH, f) 2. Lepidolite is a lithium-rich member of the isomorphic series of Al-Li and Fe-Li, and its Al-Li series is incomplete isomorphic. The analysis data prove that all lepidolite contains a certain amount of fluoride ions. The higher the lithium content, the higher the fluorine content.
Lepidolite has cleavage similar to mica, and its color ranges from purple to pink. When melted, it can foam and produce a deep red lithium flame. Insoluble in acid, but it will also be affected by acid after melting.
Lepidolite, also known as lepidolite, is generally a flaky or scaly aggregate. There is spherical lepidolite in Lushi County, Henan Province, which is a special form. It is rosy, light purple, sometimes white, and turns dark brown after weathering. Transparent. Glass luster, cleavage surface shows pearl luster. Hardness 2-3. Specific gravity is 2.8-2.9. This sheet is elastic. It is one of the main raw materials for extracting rare metal lithium. Lepidolite often contains rubidium and cesium, which is also an important raw material for extracting these rare metals.
Mica minerals can be formed under various geological conditions. Biotite is one of the main rock-forming minerals of igneous rocks, which is distributed in most plutonic and hypabyssal rocks. Muscovite is also a widely distributed rock-forming mineral, which occurs in igneous rocks, sedimentary rocks and metamorphic rocks. Phlogopite is mainly produced in ultrabasic rocks and magnesium marble. Many mica with industrial value are mainly produced in pegmatite and metamorphic rocks. A large area of phlogopite in metamorphic rocks is the product of metasomatism of volatile magmatic rocks to surrounding rocks. Fine-grained muscovite and paragonite, also known as sericite, are usually associated with hydrothermal alteration. Lepidolite almost exists only in granite pegmatite and high temperature gas-generated hydrothermal deposits related to granite. The mica species of metamorphic origin are related to the composition and metamorphic degree of the original rock, and magnesium-rich carbonate rocks are easy to become phlogopite. Aluminum-rich rocks are easily metamorphic to muscovite and biotite.
Vanadium mica in sandstone (produced in sandstone)
Chemical composition of vanadic mica: k (v, al, mg) 2alsi3o 10 (oh) 2. The Y ions are mainly vanadium and aluminum, and the isomorphic mixture includes magnesium, Fe3+, Fe2+ and chromium. Chemical analysis data; Silica 48.05%, alumina 15.00%, vanadium dioxide 14.62%, phosphorus pentoxide 0. 13%, magnesium oxide 4.32%, calcium oxide 0.34%, iron oxide 0.56%, titanium dioxide 0.38%.
The color, shape and transmitted light of vanadic mica are green, and its identification characteristics are multicolor. Vanadite mica is produced in carbonaceous slate with high organic carbon content, and coexists with chrome vanadium hydromica, chrome vanadium muscovite and barium vanadium hydromica. Most of the crystals of vanadic mica are bright green fine fibers, and a few are flaky.
Chromite (muscovite variety, monoclinic system) (muscovite variety. Purple Shi Ying monoclinic system)
Chemical composition of chromite mica: KAl2[Si3AlO 10](OH, F)2. The ideal composition is that octahedral flake contains al, and it can also be replaced by Fe 3+, Mg, Fe 2+ or even Mn, Cr, V, etc. Chromite mica has a highly complete cleavage and a pale white color. The sheet is elastic.
Chromite is one of the widely distributed rock-forming minerals, which exists in three types of rocks.
References:
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