Chemical composition as hematite Fe2O3, the crystal belongs to trigonal system of oxide minerals. It is homogenous with maghemite of equiaxed crystal system . Often has a plate-like crystal; the polarizer: blood red, orange, pale yellow; aggregates generally flaky, scaly, kidney-shaped, oolite, block or the like earthy. Was reddish brown, iron steel gray to black and other colors, streaks are cherry red, semi-metallic luster to the metal. Moss hardness is 5.5 to 6.5 , specific gravity is 4.9 to 5.3 . When the mineral particles are 0.83 mm , the specific magnetic susceptibility is 290 × 10 - 6  , Resistors 10 ~ 10 - 3 and a dielectric constant of 25. The relative atomic mass of iron is 55.845 .
Hematite is one of the most economically important minerals. There are only a few places where hematite has perfect metallic flash rhombohedral crystals. In more cases, the crystals are often flat, and some form a thin plate. Some of the samples are clustered into a rose-like shape called iron rose . Sometimes it is a scaly aggregate called mirror iron ore . All these well- crystallized hematite variants are black, but the streaks , ie the color of the mineral powder, are all red. The so-called kidney iron ore is this red, and the kidney iron ore is some radial aggregate. Has a kidney-like surface. Red is the color of most earthy hematite without crystalline form.
Hematite is a secondary mineral widely distributed among various rocks . It appears in finely dispersed grains in many igneous rocks . In special cases, it forms huge blocks in regional metamorphic rocks. In red sandstone , hematite is a cement of quartz particles and colors the rock. To economically worth mining, it must contain thousands of ten thousand tons of hematite, a large number of such reserves is deposition of scale caused, there are many of these iron ore in the former Cambrian strata, they usually contain silicon Impurities, the Longyan iron ore mine in Xuanhua , Hebei , and the Ningxiang iron ore mine in Hunan are all hematite deposits formed by sedimentation.
World famous deposits include Lake Superior and Clinton in the United States , Krivo Ilog in Russia , and Minas Grace in Brazil . Famous Chinese origin Liaoning Anshan, Jingtieshan, Daye, Hubei, Hunan and Hebei Xuanhua Ningxiang.
Hematite often contains Ti , Al , Mn , Fe2 instead of the isomorphism  , Ca, Mg and a small amount of Ga, Co. Often containing rutile titanium ore micro-inclusions. There are often mechanical inclusions of SiO2 and Al2O3 in the cryptocrystalline dense block . Fibrous or earthy water. According to the composition, titanium hematite, aluminum hematite, magnesium hematite, water hematite and other varieties can be classified.
The relationship between the morphological characteristics of hematite and its forming conditions is that hematite, which is generally formed by hydrothermal action, can be in the form of plates, flakes or rhombohedrons; mica hematite is a product of sedimentary metamorphism; And renal hematite is a product of sedimentation.
Hematite is formed under oxidizing conditions, and large-scale hematite deposits are mostly related to hydrothermal action or sedimentation. Hematite can form sedimentary metamorphic iron ore, mainly composed of magnetite, hematite, and pseudo-hematite, and is symbiotic with quartz and chlorite . A contact metamorphic primarily hematite and magnetite, brass ore, bornite, pyrite and other sulfides and the magnetic garnet, diopside, phlogopite, actinolite intergrowth. In nature, magnetite and hematite can be transformed into each other. When the oxygen fugacity increases, the magnetite can be oxidized to hematite; if the crystal form of the original magnetite remains , it is called pseudo- hematite. If the magnetite is only partially converted to hematite, it is called pseudohematite. When the oxygen fugacity is reduced, the hematite can be reduced to magnetite; if the crystal form of hematite remains, it is called maghemite.
Maghemite : γ- Fe2O3 , which often contains a mixture of Mg , Ti and Mn in its chemical composition . Isometric crystal system, pentagonal tritetrahedral crystal, mostly granular aggregate, dense block, often with magnetite illusion. The color and streaks are brown, hardness 5 , specific gravity 4.88 , strong magnetic.
Maghemite is mainly formed by the secondary change of magnetite under oxidizing conditions. The Fe2+ in the magnetite completely replaces " 3Fe2+ → 2Fe3+ " with Fe3+ , so the octahedral position occupied by 1/3Fe2+ creates a vacancy. In addition, maghemite can be formed by the dehydration of fibrite, and also by the organic action of iron oxides.
The aggregates of hematite have various forms and form some mineral subspecies , namely:
　　 (1) Mirror iron ore  It is a collection of metallic lustrous rosette or flaky hematite.
　　 (2) Mica Hematite  Metallic lustrous crystalline fine scaly hematite.
(3) Wart or kidney hematite  Hematite in the form of warts or kidneys.
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