Hematite hematite is anhydrous iron oxide ore, its chemical formula is Fe2O3, the theoretical iron content is 70%. This kind of ore often forms huge ore deposits in nature, and it is the main ore of industrial production from the burial and mining amount.
Siderite siderite for carbonate iron ore, chemical formula FeCO3, the theory of iron content of 48.2%. In nature, siderite, which has an industrial value, is less than three other minerals. Siderite is easily decomposed and oxidized to limonite. Generally iron content is not high, but after the decomposition of CO2 heating, not only iron content significantly improved, but also become porous, reducing nature is very good.
Limonite and limonite are hydrous iron oxide ores, which are produced by weathering of other ores. They are widely distributed in nature, but few deposits are found. Its chemical formula is nFe2O3. MH2O (n=1 ~ 3, m=1 ~ 4). Limonite is actually made up of a mixture of goethite (Fe2O3, H2O), goethite (2Fe2O3, H2O), iron oxides containing different crystalline water, and clay matter. Most of the iron minerals in limonite exist in the form of 2Fe2O3 and H2O.Generally, iron content of brown iron ore is 37% ~ 55%, and sometimes phosphorus is higher. The water absorption of limonite is very strong, and it usually attracts a large amount of water. After roasting or heating into the blast furnace, the free water and crystalline water are removed. Therefore, the porosity of the ore is increased, which greatly improves the reducibility of the ore. Therefore, limonite is better than hematite and magnetite in reduction. At the same time, the iron content of the ore is increased by removing the water.
Magnetite mainly contains iron minerals, magnetite, and its chemical formula is Fe3O4, in which FeO=31%, Fe2O3=69%, the theoretical iron content of 72.4%. This ore sometimes contains TiO2 and V2O5 composite ore, called titanium magnetite or vanadium titanium magnetite. Magnetite has strong magnetism, crystals often become eight faces, and a few are rhombic twelve bodies. Often aggregate into dense clumps, color streak iron black, semi metallic luster, relative density of 4.9 to 5.2, the hardness of 5.5 ~ 6, no cleavage, gangue is mainly quartz and silicate. Poor reducibility, generally containing harmful impurities, sulfur and phosphorus higher.
Any of various iron minerals, consisting of their minerals, can be divided into 4 main groups: magnetite, hematite, limonite and siderite. Because of their chemical composition, crystalline structure and geological conditions, various iron ores have different external morphologies and physical characteristics.
