The general name for potassium, aluminum, magnesium, iron, lithium and other layered structure aluminosilicates. Polymorphism is common, among which the monoclinic crystal system is common, followed by the trigonal crystal system, and the others are rare. The most common mineral species among mica minerals include biotite, muscovite, phlogopite, lepidolite, sericite, etc. Mica usually takes the form of pseudo-hexagonal or rhombus-shaped plate, flake, or columnar crystals. The color varies with changes in chemical composition, and mainly becomes darker as the Fe content increases. Muscovite is colorless, transparent or light-colored; biotite is black to dark brown, dark green and other colors; phlogopite is yellow, brown, green or colorless; lepidolite is lavender, rose red to gray. Glass luster, pearl luster on the cleavage surface. Mohs hardness is generally 2 to 3.5, and specific gravity is 2.7 to 3.5. Cleavage of parallel bases is extremely complete. Muscovite and phlogopite have good electrical insulation, non-thermal conductivity, acid resistance, alkali resistance and voltage resistance, so they are widely used to make insulating materials in the electronic and electrical industries. Mica chips and powder 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. The names recorded in ancient Chinese books include: Huapilian, Tianbing, Tianpi, Dijin, Laoguajin, Thousand Layer Paper, Yuanmian, Yunmichi, Xionghei, etc. The pigments used in Cave 112 of the Tang Dynasty in the Mogao Grottoes in Dunhuang are shiny and shiny. According to X-ray diffraction analysis, they are made from finely ground natural muscovite mica. The color rendering is excellent.
Although China has known and utilized muscovite and phlogopite for a long time, the formal exploration work on mica deposits was started after the founding of the People's Republic of China. Starting in 1952, Sichuan Dan Mica was The muscovite deposits in Tuguiwula, Inner Mongolia, have been surveyed and explored and achieved good results. In 1958, the National Mica Conference was held in Fanzhi, Shanxi, and it was decided to vigorously carry out the survey and exploration of mica. In that year, the discovery of mica deposits in Altay, Xinjiang, played a major role in the development of mica resources in China. It also provided a basis for the survey of mica deposits. Exploration work has accumulated experience. Subsequently, the magnesium-silica muscovite deposit in Donghai, Jiangsu was discovered and utilized by industry, adding new industrial mica species to China. Mica deposits have been discovered in Wula Mountains, Dabie Mountains, Qinling Mountains, Liaoning, Sichuan and Yunnan and other places in Inner Mongolia, expanding mica resources. Since the 1980s, departments such as building materials, geology and mining have carried out general surveys of crushed mica and sericite mines. After detailed investigation, the crushed mica mine at Shankou, Tanzhuang Township, Lingshou, Hebei Province was discovered, and sericite mineral spots were discovered in Inner Mongolia, Liaoning, Hubei and other places. Progress has also been made in the industrial application research of crushed mica and sericite.
From the 1950s to the mid-1970s, China listed muscovite and phlogopite as strategic resources. The first mine was the Danba mica mine in Sichuan, and later in Xinjiang, Inner Mongolia, Shanxi, Hebei, and Shandong. Mica mines in , Henan, Shaanxi, Yunnan and other 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, an industrial raw material, was 1,700 to 2,500t. After 1978, the output declined year by year due to fundamental changes in the mica consumption structure.