Open classification of hematite: ore, mineral, physical chemistry, geology, mineral Hematite is Fe2O3 in chemical composition, and its crystal belongs to ternary oxide mineral. The western name comes from the Greek meaning of "blood", which means that this mineral is often red. It is an oxide of iron and the main mineral of iron. Although other metals are gradually replacing iron, iron is still the most important metal. Therefore, hematite is one of the most important economic minerals. There are only a few places where hematite has perfect metallic sparkling diamond crystals. However, in more cases, crystals tend to be flat, and more importantly, they form thin plates. Some samples are disk-shaped and clustered into roses, which are called iron roses. Sometimes it is a scale-like aggregate called specularite. These well-crystallized hematite varieties are all black, but the stripes, that is, the color of mineral powder, are red. This is the so-called kidney-shaped iron ore, which is a radial aggregate with a kidney-shaped surface. Red is the color of most earthy hematite without crystal morphology. Ochre is this red earthy hematite, which was once used as a pigment. Hematite is an accessory mineral widely distributed in various rocks. It appears in many igneous rocks in the form of fine particles, and forms huge blocks in regional metamorphic rocks under special circumstances. In red sandstone, hematite is the cement of timely particles, which dyes rocks. If it has economic value, it must contain tens of millions of tons of hematite, which is caused by large-scale deposition. There are many such iron ores in Precambrian strata, which usually contain silicon impurities. Iron-rich ore with iron content of at least 50% is enriched by leaching silicon dioxide with rainwater. These rich minerals are the source of iron in the world, but their reserves are decreasing. In order to make up for this deficiency, mining companies are turning their attention to the original iron-containing buildings, the so-called iron-containing quartzite. This kind of rock contains only 25-30% iron, but its reserves are very huge. Iron minerals in low-grade iron ore can be enriched by mechanical means. In this way, iron-bearing quartzite will be a lasting iron ore resource. Hematite is iron oxide, which is heavy and hard. Hematite contains 70% iron and can be produced in large quantities, so it is the most important iron ore. Hematite is named for its crimson color. There are several forms of hematite, and people give them different names according to their different forms. For example, shiny steel-gray crystals are called specularite, scaly ones are called mica hematite, soft ones are called ochre, many spherical ones are called kidney iron ore, and fibrous ones are called pen iron ore. Hematite is widely distributed. Hematite can be generated in many cases, but the most important hematite deposit is sedimentary. Hematite is usually produced with magnetite. In addition to ironmaking, powdered hematite is also used as a red pigment and abrasive. Large hematite deposits can be found and mined on every continent. 196 1 year, the Soviet union replaced the United States as the largest producer. The United States is followed by France, Canada, China, Sweden and Australia. In the United States, since the end of 19, the largest mineral producing area is in Precambrian rocks in the Great Lakes region. It is homogeneous and multi-image with magnetite with equiaxed crystal system. Single crystals are often rhombic and plate-shaped, and the aggregate forms are diverse, such as flake, scale (crystal), granular, oolitic, kidney-shaped, earthy, dense block and so on. The microcrystals are iron black to steel gray, the aphanitic is dark red, the stripes are cherry red, the metallic luster is semi-metallic luster, the Mohs hardness is 5.5-6.5, there is no cleavage, and the specific gravity is 5.0-5.3. The flaky hematite aggregate with iron black and metallic luster is called specularite; The scaly hematite aggregate with gray and metallic luster is called mica hematite; Red-brown and dull is called ochre; Oolitic or renal hematite is called oolitic or renal hematite. Hematite is an iron mineral widely distributed in nature, which is an important raw material for ironmaking and can also be used as a red pigment. Most important hematite deposits are metamorphic, and some are formed by weathering and colloidal precipitation in hydrothermal or large water basins. World-famous mineral deposits include Lake Superior and Lake Clinton in the United States, Krivojillo in Russia and Manas Grace in Brazil. China is famous for Anshan in Liaoning, Jingtieshan in Gansu, Daye in Hubei, Ningxiang in Hunan and Xuanhua in Hebei. [Crystal Chemistry] Ti, al, Mn, Fe2, Ca, Mg and a small amount of Ga and Co are often replaced by isomorphism; Microinclusions usually contain rutile and ilmenite. Mechanical inclusions such as SiO2 _ 2 and Al _ 2O _ 3 often exist in cryptocrystalline dense blocks. Fibrous or earthy containing water. According to the composition, it can be divided into titanium hematite, aluminum hematite, magnesium hematite, hydrohematite and other varieties. [Structure and morphology] Tripartite crystal system, arh=0.542 1nm, α=55. 17'; Z=2 .ah=0.5039 nm，ch = 1.3760nm； Z=6. Corundum structure. When Ti is substituted in the composition, the unit cell volume will increase. However, the replacement of aluminum reduces the battery volume. Complex triangular cubic crystal, D3d-3m(L33L23PC). Perfect crystals are rare. Common simplex: parallel double-sided C, hexagonal column A, rhombohedral R, U, E, hexagonal bipyramid N. Parallel to the intersection direction, there are three groups of crystal face patterns such as stripes, triangular pits or growth cones. It is called polycrystalline twin, and (000 1) is called interspersed twin or contact twin. It often appears in the form of crystal plate, scale, granular and cryptocrystalline dense block, oolitic, pea-like, kidney-like, powder and other aggregate forms. [Physical properties] Steel gray to iron black, often with light blue actinide color; Aphanitic or powdery is dark red to bright red. Unique cherry red or reddish brown stripes. Metallic or semi-metallic luster, sometimes dull. No cleavage. Because twins have conflicts. The hardness is 5~6. The relative density is 5.0~5.3. Under the polarizer: blood red, orange yellow, grayish yellow. Uniaxial crystal (-), No=2.988, Ne=2.759. 【 Occurrence and assemblage 】 It was formed under oxidation conditions, and large hematite deposits were mostly related to hydrothermal solution or sedimentation. Hematite can form sedimentary metamorphic iron ore, which is mainly composed of magnetite, hematite and pseudohematite, accompanied by timely and chlorite. Contact metamorphic hematite is mainly associated with sulfides such as magnetite, chalcopyrite, bornite and pyrrhotite, as well as garnet, diopside, phlogopite and actinolite. In nature, magnetite and hematite can be transformed into each other. When oxygen fugacity increases, magnetite can be oxidized into hematite; If the crystal form of primary magnetite remains, it is called pseudohematite. If magnetite is only partially converted into hematite, it is called pseudohematite. When oxygen fugacity decreases, hematite can be reduced to magnetite. If the crystal form of hematite still exists, it is called polybiotite. [Identification features] Cherry red or reddish brown stripes are its characteristics. It has various forms and no magnetism, and can be distinguished from similar magnetite and ilmenite. [Industrial Application] One of the important iron ore minerals. Titanium, gallium, cobalt and other elements can be comprehensively utilized when they reach a certain amount. Iron oxide can be used as a mineral pigment. The name of medicinal hematite is ochre, also known as ochre, ochre, iron vermilion, nail head ochre, red stone and red ochre. Efficacy: calming the liver and suppressing yang; Major towns move down; Cool blood and stop bleeding. Hematite with iron black, metallic luster and flake shape is called specularite; Known as mica hematite, it is bluish gray with metallic luster and scales, and was called "Yunzi Iron" in ancient China. Dark reddish-brown soil is called ochre, which was called "ochre" in ancient China, and "ochre" generally refers to hematite. Hematite is widely distributed. Hematite can be produced by various endogenous, exogenous or metamorphic processes. Longyan Iron Mine in Xuanhua, China and Ningxiang Iron Mine in Hunan are both hematite deposits formed by sedimentation. Hematite is often produced with magnetite in sedimentary metamorphic and contact metamorphic iron ores. You can also go to Baidu Encyclopedia at baike.baidu.com, where there are pictures for reference.