What is mica?

Mica is the most widely distributed rock-forming mineral, and it is the general name of layered aluminosilicate such as potassium, aluminum, magnesium, iron and lithium. Mica is generally polymorphic, of which monoclinic system is common, followed by tricrystal system, and the rest are rare. The most common minerals in mica are biotite, muscovite, phlogopite, lepidolite and sericite. Mica is usually a pseudo-hexagonal or rhombic plate, flake and columnar crystal. The color changes with the change of chemical composition, and darkens mainly with the increase of iron content. Muscovite is colorless, transparent or light; Biotite is black to dark brown and dark green. Phlogopite is yellow, brown, green or colorless; Lepidolite is lavender, rose red to gray. Glass luster, cleavage surface has pearl luster. Mohs hardness is generally 2 ~ 3.5 and specific gravity is 2.7 ~ 3.5. The cleavage of the parallel bottom surface is extremely complete. Muscovite is one of the widely distributed rock-forming minerals, which exists 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 and phlogopite have good electrical insulation, thermal conductivity, acid resistance, alkali resistance and pressure resistance, so they are widely used to manufacture insulating materials for electronics and mica gas industry. Mica chips and powder are used as fillers. Lepidolite is also the main mineral raw material for extracting lithium.

Mica minerals have been used by human beings for a long time because of their large crystals and bright colors. The appellations in China ancient books are: Huapi Lian, Tianpi, Laojiaojin, Melaleuca Paper, Yuanmian, Red and Xionghei. The pigments used in Cave 1 12 of Dunhuang Mogao Grottoes are shiny. By X-ray diffraction analysis, they are finely ground natural muscovite. Excellent color rendering effect.

Although China has known and used muscovite and phlogopite for a long time, the formal exploration of mica deposits was after the establishment of People's Republic of China (PRC). From 65438 to 0952, the general survey and exploration were carried out in Danba, Sichuan and Tuguiwula muscovite deposit, Inner Mongolia, and good results were achieved. 1958, a national mica conference was held in Fan Shi, Shanxi province, and it was decided to vigorously carry out mica survey and exploration. The discovery of mica ore in Altay, Xinjiang, played a great role in the development of mica resources in China, and also accumulated experience for the general survey and exploration of mica ore. Subsequently, the discovery of muscovite deposit of Mg-Si in Donghai, Jiangsu Province was used in industry, which added a new industrial mica variety to China. Mica deposits have been discovered in Wulashan, Dabie Mountains, Qinling Mountains, Liaoning, Sichuan, Yunnan and other places in Inner Mongolia, expanding mica resources. Since 1980s, the departments of building materials, geology and mineral resources have carried out a general survey of broken mica and sericite. Up to now, Lubaishan Village in Lingshou, Hebei Province is the largest production and processing place of crushed mica and biotite in China. After detailed investigation, broken mica ore was found in Shanmenkou, Tanzhuang Township, Lingshou, Hebei Province, and sericite occurrences were found in Inner Mongolia, Liaoning, Hubei and other places. The industrial application research of broken mica and sericite has also made progress.

From 1950s to 1970s, China listed muscovite and phlogopite as strategic resources. The earliest mica mine was Danba mine in Sichuan, and then mica mines in Xinjiang, Inner Mongolia, Shanxi, Hebei, Shandong, Henan, Shaanxi, Yunnan and other provinces were successively mined. The main state-owned mines are Altay in Xinjiang, Danba in Sichuan and Tuguiwula in Inner Mongolia, as well as hundreds of county, township and individual mines. Before 1978, the annual output of industrial raw material mica was 1 700~2 500t, and after 1978, the output decreased year by year, because the consumption structure of mica changed fundamentally.