Mineral Encyclopedia – illite

Release date: 2022-12-09

Illite is a layered clay mineral similar to mica, also known as hydromuscovite.

The flaky or strip-like crystals of illite are very small, and they generally appear to us as earthy. Because of impurities, illite is generally yellow, brown, green and other colors, but if the purity is high, it should be white.

Much illite is formed by weathering of muscovite or potassium feldspar, and illite can be transformed into other clay minerals.

The crystals are mainly monoclinic hydrous layered silicate minerals. In the formula, R2+ represents divalent metal cations, mainly Mg2+﹑Fe2+ and so on. The crystal structure is basically the same as that of muscovite, and it also belongs to the 2-octahedral type of the 2:1 structural unit layer. Crystals have polymorphic variants such as 1M, 2M, 1Md and 3T. Unlike muscovite, the amount of K+ in the interlayer is less than that of muscovite, and there are water molecules. Therefore illite is also called water muscovite. Others use it as a synonym for hydromica. Illite is often in the form of very small scaly crystals, irregular or angular flakes under the transmission electron microscope, and sometimes incomplete hexagonal and lath-like forms, usually in the form of soil-like aggregates. Pure illite clay is white, but it is often dyed yellow, green, brown and other colors due to impurities. The bottom surface is completely cleaved. Mohs hardness 1-2. Specific gravity 2.6 ~ 2.9. Illite is a common clay mineral, often formed by weathering of muscovite and potassium feldspar, and produced in argillaceous rocks, or formed by alteration of other minerals. It is often an intermediate transitional mineral that forms other clay minerals. Illite clay can be used as a new type of ceramic raw material, as a flux for high-temperature-resistant cylinders, and to absorb cesium in nuclear waste treatment to prevent radiation, and can be used as a filler for cosmetics or plastics. Pure white illite can also replace kaolinite as paper-making coating, and can also be used to produce spraying materials for automobile shells and welding electrodes. Illite is a new mineral in our country. Illite mines have been discovered in Duchuantou Village, Shuangchao Township. Illite has excellent chemical and physical properties such as potassium-rich, high-alumina, low-iron, smooth, bright, delicate, and heat-resistant.

Illite has a wide range of industrial uses, and can be used to make potash fertilizers, advanced coatings and fillers, ceramic accessories, advanced cosmetics, soil conditioners, poultry feed additives, skeleton ingredients and cement ingredients for high-rise buildings, pollution purification and environmental protection in the nuclear industry. Among them, trace elements can be used to make the outer coating of the space shuttle. Especially in the three major industries of papermaking, cosmetics and ceramics, illite has great application value.

Illite sticky (rock), also known as hydromica clay, is white or off-white in appearance, gray or black with more impurities, soil-like, brittle, brittle, fine and smooth in texture, and low in hardness. Swelling, looseness and turbidity. In the coal-measure strata, the illite claystone is often produced in the form of lenticular or layer-like in the coal seam mixed with gangue.

The mineral composition of illite clay (rock) is mainly illite, containing a small amount of kaolinite, montmorillonite, chlorite, pyrophyllite, etc. Detrital minerals are common quartz, feldspar, iron and so on. The chemical composition of illite clay (rock) changes greatly due to other impurities. Except for the large difference in the content of SiO2 and Al2 O3, K2 O and Na2 O are relatively stable, generally K2 O is 6%~9%, Na2 O Between 0.5% and 1.5%.

Illite clay (rock) is the most widely distributed clay rock. There are not many pure illite clay (rock) and they are often mixed with other clay minerals to form complex clay rocks. If the composition is pure, illite clay deposits can be formed. For example, illite clay (rock) is produced in Sichuan, western Qibei, Hebei Xiaofu and other places in my country. Illite clay (rock) has a wide range of uses. In the ceramic industry, illite clay (rock) is used as a raw material for the production of high-voltage electric porcelain and daily-use porcelain. In the chemical industry, it is used as a filler for papermaking, rubber, and paint. Preparation of potassium fertilizer, etc.