What is mica? Use and origin are explained in detail!

Published: 2021/11/12

  1. What is mica?

  Mica (mica or glimmer) is one of the most widely distributed rock-forming minerals, a general term for layered structure aluminosilicates such as potassium, aluminum, magnesium, iron, and lithium. Mica generally has polymorphism, among which the monoclinic crystal system is common, followed by the trigonal crystal system, and the others are rare. The most common mineral species in mica group minerals are sericite, muscovite, phlogopite, lepidolite, biotite and so on. Mica is usually in the form of pseudo-hexagonal or rhombic plate, sheet, and columnar crystals, and sheet mica has the greatest development and utilization value. The color varies with the chemical composition, mainly becoming darker with the increase of iron content. Muscovite is colorless, transparent or light-colored; biotite is black to dark brown, dark green and other colors; phlogopite is mainly yellow, brown, green or colorless; lepidolite is lavender, rose red to gray. Vitreous luster, pearly luster on the cleaved surface. The Mohs hardness is generally 2 to 3.5, and the specific gravity is 2.7 to 3.5. The cleavage of parallel bases is very complete. Muscovite is one of the widely distributed rock-forming minerals, and it is produced in all three rock types. The argillaceous rock can form sericite in the process of metamorphism in low-level regions, and become muscovite in a slightly higher degree of metamorphism. A large amount of muscovite was formed in the late stage of acid magma crystallization and pegmatite. It can also be formed during the alteration process from high temperature to medium and low temperature. The so-called greisenization is one of the high-temperature alterations, which can form a large amount of muscovite. The so-called sericitization is one of the medium and low temperature alterations, which can form a large amount of sericite, mainly in sheet structure. Muscovite is weathered and broken into extremely fine scales, which can be either clasts in clastic sediments or one of the mineral components of argillaceous rocks.

  Both muscovite and phlogopite have good insulation properties, high temperature resistance, luster, stable physical and chemical properties (acid resistance, alkali resistance and pressure resistance), good heat insulation, elasticity and toughness, and are stripped The performance of forming a transparent sheet with elasticity. Therefore, it is widely used to make insulating materials in the electronics and electrical industries. Mica fragments and powders are used as fillers, etc. Lepidolite is also the main mineral raw material for extracting lithium.

  Mica minerals have been used by humans for a long time due to their large crystals and bright colors. There are records of its titles in ancient Chinese books: Huapilian, Tianbing, Tianpi, Dijin, Laobaojin, Thousand-layer Paper, Yuanmian, Yunmichi and Xionghei. The pigment used in Cave 112 of the Tang Dynasty in the Mogao Grottoes in Dunhuang is shining brightly. According to X-ray diffraction analysis, it is made of natural muscovite after finely grinding. Excellent color rendering.

  Although China has recognized and utilized muscovite and phlogopite for a long time, the formal exploration of mica deposits began after the founding of the People's Republic of China. Since 1952, the muscovite deposits in Danba, Sichuan and Tuguiwula, Inner Mongolia have been successively carried out. The census exploration has been carried out and good results have been obtained. In 1958, the National Mica Conference was held in Fanzhi, Shanxi, and it was decided to vigorously carry out the general survey and exploration of mica. In that year, the discovery of the Altay mica deposit in Xinjiang played a great role in the development of mica resources in China. Exploration work has accumulated experience. Subsequently, the discovery of the magnesium-silicon muscovite deposit in the East China Sea of ​​Jiangsu Province and its utilization by industry added new industrial mica species to China. Mica deposits in Inner Mongolia Wulashan, Dabie Mountain, Qinling, Liaoning, Sichuan and Yunnan have been discovered one after another, expanding mica resources. Since the 1980s, building materials, geological and mining departments have carried out general surveys of crushed mica and sericite mines. So far, Lubai Mountain Village in Lingshou, Hebei Province is the largest production and processing place of crushed mica and biotite in China. After detailed investigation, the country's largest sericite deposit was found in Chuzhou, Anhui and other places, with a reserve of over 100 million tons and high quality. It is basically an open-pit mica mine with a flaky structure that is easy to develop and utilize. Daliu, Chuzhou, which is already under construction The town sericite industrial park is the largest sericite production base in the country.


  From the 1950s to the mid-1970s, China once listed muscovite and phlogopite as strategic resources. The earliest mines were Danba Mica Mine in Sichuan, and then Xinjiang, Inner Mongolia, Shanxi, Hebei, Shandong, Henan, Shaanxi, Yunnan, etc. Mica mines in provinces and autonomous regions have been mined one after another. The main state-owned mines include Xinjiang Altay, Sichuan Danba, Inner Mongolia Tuguiwula and other mines, as well as hundreds of county offices, townships and individual mines. Before 1978, the annual output of mica as an industrial raw material was 1 700 to 2 500t. After 1978, the output decreased year by year because of the fundamental change in the consumption structure of mica.

  2. Mica sheet

  Mica sheets are composed of polysilicon muscovite, quartz, garnet and rutile, etc. Albite, zoisite and chlorite can appear, garnet is rich in Fe and Mg, and Si in polysilicon muscovite can reach 3.369. Also a high pressure combination. It has thermal resistance function of insulation and low loss, and it is also a good blackbody.

  Natural mica sheet is made of thick mica after peeling, thickness setting, cutting, drilling or punching. It has a certain thickness and a certain shape. , aerospace, aviation, communications, radar, heat-resistant skeleton film, etc. as raw and auxiliary materials. Divided into: electric heater chip, electric heater protection sheet, gasket, electronic tube sheet, bulb sheet, because the material is a natural mineral product, it has the characteristics of no pollution, insulation, and good voltage resistance, and various specifications can be punched according to customer needs natural mica flakes.

  3. Mica powder

  Mica powder is a kind of non-metallic mineral, which contains many kinds of components, mainly including SiO 2 , the content is generally about 49%, and the content of Al 2 O 3 is about 30%. Mica 1 has good elasticity and toughness. Insulation, high temperature resistance, acid and alkali resistance, corrosion resistance, strong adhesion and other characteristics, it is an excellent additive. It is widely used in electrical appliances, welding electrodes, rubber, plastics, papermaking, paints, coatings, pigments, ceramics, cosmetics, new building materials and other industries, and has a wide range of uses. With the continuous development of science and technology, people have opened up new application fields.

  4. Phlogopite

  Phlogopite, one of the muscovite minerals, is an aluminum silicate containing iron, magnesium and potassium. If the iron in the phlogopite composition is not too much, it can be used as an electrical insulating material, so it plays an important role.

  Phlogopite is divided into dark phlogopite (various shades of brown or green, etc.) and light phlogopite (various shades of light yellow).

  Light-colored phlogopite is transparent and glassy; dark-colored phlogopite is translucent. Vitreous luster to semi-metallic luster, cleavage surface is pearly luster.

  The flakes are elastic and do not conduct electricity. Colorless or brownish-yellow under transmitted light under a microscope. Pure phlogopite is the first-class insulating material in the electrical industry, and is also widely used in real stone paint.

  5. Synthetic mica

  Synthetic mica, also known as fluorine phlogopite, is made of chemical raw materials through high-temperature melting and cooling crystallization. The fractional formula of its single crystal is KMg3(AlSi3O10)F2, which belongs to the monoclinic system and is a typical layered silicate.

  Many of its properties are superior to natural mica, such as temperature resistance up to 1200 ° C, under high temperature conditions, the volume resistivity of synthetic fluorophlogopite is 1000 times higher than that of natural mica, good electrical insulation, low vacuum outgassing at high temperature, As well as acid and alkali resistance, transparency, peelability and elasticity, it is an important non-metallic insulating material for modern industries and high technologies such as motors, electrical appliances, electronics, and aviation.

  Muscovite is the most used in industry, followed by phlogopite. It is widely used in building material industry, fire protection industry, fire extinguishing agent, welding rod, plastic, electrical insulation, paper making, asphalt paper, rubber, pearlescent pigment and other chemical industries. Ultrafine mica powder can be used as functional filler in plastics, coatings, paints, rubbers, etc., which can improve its mechanical strength, enhance toughness, adhesion, anti-aging and corrosion resistance. In addition to having extremely high electrical insulation, acid and alkali corrosion resistance, elasticity, toughness and sliding properties, heat resistance and sound insulation, and small thermal expansion coefficient, etc., it is also the first to introduce the smooth surface of the sheet body, large diameter-to-thickness ratio, regular shape, and attachment. Focus on strong and other characteristics.

  In the industry, it is mainly used for its insulation and heat resistance, as well as acid resistance, alkali resistance, compression resistance and stripping properties, and is used as an insulating material for electrical equipment and electrical equipment; secondly, it is used to manufacture steam boilers and furnaces for smelting furnaces. Windows and mechanical parts.

  Mica chips and mica powder can be processed into mica paper, and can also replace mica sheets to produce various insulating materials with low cost and uniform thickness.

  Medicinal: Mica, sweet in taste, flat in nature: "The Classic": "maintain dead skin muscles, stroke, cold and heat, such as on a car and boat, eliminate evil spirits, calm the five internal organs, benefit the essence, and improve eyesight.". "Bie Lu": "The lower qi strengthens the muscles, continues to nourish the middle, treats five fatigue and seven injuries, deficient and less qi, and stops dysentery." Dexterous, prolong life.

  Mica has high dielectric strength and high resistance, low dielectric loss and excellent dielectric properties such as arc resistance and corona resistance, and it has a hard texture, high mechanical strength, high temperature resistance and rapid temperature changes, and acid resistance. Good physical and chemical properties such as alkali, so it is widely used in radio industry, aviation industry, motor manufacturing, it is also widely used in coatings, paints, plastics, linoleum, papermaking, oil field drilling, decorative makeup and other industries, it can reduce ultraviolet rays in paints or other light and heat damage to the paint film, increase the acid resistance, alkali resistance and electrical insulation properties of the coating, improve the frost resistance, corrosion resistance, toughness and compactness of the coating, reduce the gas permeability of the coating, and prevent spots and cracked. Mica powder can also be used in roofing materials to prevent rain, heat preservation, heat insulation, etc. Mica powder can be mixed with mineral wool resin paint to decorate concrete, stone, and brick exterior walls. Mica powder can be used for linoleum, pipeline mortar, Cementing agent; In rubber products, mica powder can be used as lubricant, release agent, and filler for high-strength electrical insulation and heat-resistant, acid-resistant and alkali-resistant products. Mica can also be used as mica paper, mica board, mica ceramics, pearlescent mica pigments, mica casting products, etc.

  In the industry, it is mainly used for its insulation and heat resistance, as well as acid resistance, alkali resistance, compression resistance and stripping properties, and is used as an insulating material for electrical equipment and electrical equipment; secondly, it is used to manufacture steam boilers and furnaces for smelting furnaces. Windows and mechanical parts. Mica chips and mica powder can be processed into mica paper, and can also replace mica sheets to produce various insulating materials with low cost and uniform thickness.

  7. Distribution of Mica Mineral Areas

  The distribution of mica minerals in China is uneven. Although they are distributed in 20 provinces, municipalities and autonomous regions across the country, most of them are concentrated in Xinjiang, Sichuan and Inner Mongolia. 184 production areas have been found in the country, including 88 in Xinjiang, accounting for 67% of the national reserves, 27 in Sichuan, accounting for 11.4% of the national reserves; 15 in Inner Mongolia, accounting for 8.6% of the national reserves; the remaining 54, accounting for 13 of the national reserves. %, distributed in Hebei, Shanxi, Liaoning, Jilin, Heilongjiang, Shandong, Henan, Yunnan, Tibet, Qinghai and Shaanxi. The mica mine in Hebei is located in Longxing Mining Industry, Lingshou County, Shijiazhuang, in the middle of the Taihang Mountains. The strata in Lingshou County are archaic dual-quality rock formations, which are rich in mica minerals. According to the exploration of the texture department, the reserves of crushed mica reached 1.7 million tons. With high grade and good quality, it is the largest producer of crushed mica in the country. At the same time, because of its early development, it has become the largest mica processing base and the largest mica exporter in the country.

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