the basic concepts of iron ore
The ore is the mineral aggregates. Of modern technology, economic conditions, on an industrial scale from minerals processing to extract metals or other products. Originally refers to the non-metallic mineral accumulation in the parent rock solid material mined from the metal deposit has been expanded to the formation of sulfur, fluorite and barite, and the like.
Useful component (element or mineral) weight and ore the weight ratio as the ore grade ore, gold, platinum and other precious metals ore g / t ore commonly expressed as a percentage. Commonly used in ore grade to measure the value of the ore, but the composition of the same active ingredients of the ore gangue (unwanted minerals in the ore or the content of useful component is minimal and can not use the minerals) and how many of the harmful impurities affect the ore value.
iron ore classification
Generally divided into poor ores, minerals and rich ore. Sometimes only ore is divided into poor and rich ore, this division is no uniform standard, generally for each industrial sector and the mining area has its own calculation. Contains useful minerals nature and characteristics is divided into two major categories of metal ores and non-metallic ore.
iron ore varieties
Property of iron minerals wide range of iron minerals and iron minerals have been found about 300 species, of which there are more than 170 species. However, the current technical conditions, with industrial value, mainly magnetite, hematite, maghemite, ilmenite, limonite, and siderite, etc..
1 magnetite
Magnetite (Magnetite) is an iron oxide ore, the main ingredient of Fe3O4, Fe2O3 and FeO complex. Of FeO 31.03% of Fe2O3 68.97% or containing Fe 72.2%, O 27.6%, equiaxed. Single crystal often has octahedral, the less was the rhombic dodecahedron. Rhombic dodecahedron surface of decent, long diagonal direction is often now the stripes. A collection of mostly dense massive and granular. The color is iron black, streaks of black, semi-metallic luster, opaque. Hardness of 5.5 to 6.5, the proportion of 4.9 to 5.2, no cleavage, the gangue is mainly quartz and silicate. With a strong magnetic. Reductive, generally contain harmful impurities of sulfur and phosphorus higher. Can make use of magnetic separation in mineral processing (Beneficiation), very easy to handle; but because of its fine structure, it was less reduced. After after a long-term weathering into hematite. Magnetite are often a considerable number of Ti4 + to isomorphism instead of Fe3 +, accompanied by Mg2 + and V3 + accordingly instead of Fe2 + and Fe3 +, and thus the formation of some minerals, subspecies, namely:
Titanium magnetite, Fe2 + (2 + x) (1) of Fe3 + (2-2x) TixO4 (0
(3) the product of a solid solution of vanadium and titanium magnetite is more complex composition of these two minerals.
(4) chrome magnetite containing Cr2O3 up to a few percent.
(5) magnesium magnetite containing MgO up to 6.01%. The magnetite is of magmatic origin of iron deposits, contact metasomatic - hydrothermal iron ore deposits, sedimentary-metamorphic iron ore deposits, as well as a series of iron ore in the iron ore deposits related to volcanism, mineral. In addition, it is also common in the sand deposits. Rarely encountered in natural pure magnetite ore, often due to surface oxidation of part of the magnetite oxidation transition for the the half martite and the illusion of hematite. The so-called martite oxidation of magnetite (Fe3O4) into hematite (Fe2O3), but still retain their original crystal, so called martite.
(2) hematite
Hematite, hematite (Hematite), for the anhydrous oxidation of iron ore, the chemical formula of Fe2O3, the theoretical iron content of 70%. This mineral in nature, often forming huge deposits from burial and extraction, industrial production ore. By its own structural condition of the different can be divided into many categories, such as red hematite (Red hematite), specularite (Specularhematite), mica, iron ore (Micaceous hematite), clayey, hematite (Red Ocher). Hematite iron content is generally 50% to 60%, containing less harmful impurities of sulfur and phosphorus, restore better than the magnetite, hematite is an excellent raw material of iron-smelting. Hematite native, wild, regeneration of hematite, magnetite magnetic lost through oxidation after, but still preserved the illusion of the crystal shape of magnetite hematite, in martite often contain Some remnants of magnetite. Sometimes hematite weathering products also contain hematite, limonite (2Fe2O3 · 3H2O). Hematite has a semi-metallic luster, crystalline who hardness of from 5.5 to 6, earthy hematite hardness is very low, no cleavage, the relative density of 4.9 to 5.3, only a weak magnetic gangue silicate.
The Fe2O3 homogeneous in nature and more like a variant known to have two types of α-Fe2O3 and γ-Fe2O3. The former stable under natural conditions, known as hematite; which under natural conditions better than the stability of α-Fe2O3 in a metastable state, called magnetic hematite. Hematite: Fe 69.94%, O 30.06%, often with isomorphous mixed material of Ti, Al, Mn, of Fe2 + Ca and Mg and a small amount of Ga and Co Trigonal system, intact crystals rare. Crystalline hematite steel-gray, aphanitic; earthy hematite red. The streak is cherry red or bright liver color. Metal to semi-metallic luster. Sometimes gloss dim. Hardness 5 to 6. The proportion of 5 to 5.3. Hematite aggregates have a variety of forms, the formation of some minerals, subspecies, namely:
(1) specularite. With a metallic luster like a rose or a flake of hematite aggregates.
(2) mica, hematite. The metallic luster of the crystal quality of thin squamous hematite.
(3) oolitic hematite or kidney-shaped. The morphology of the Oolitic or kidney-shaped hematite.
Hematite is widely distributed in nature one of the iron minerals can be formed in various geological, hydrothermal, sedimentation, and regional metamorphism-based. In the oxidation zone, the hematite may be limonite or lepidocrocite, goethite (Goethite) the formation of the dehydration. But can also be turned into goethite and water and hematite. Under reducing conditions, hematite into magnetite, known as the illusion of magnetite. Maghemite: γ-Fe2O3, its chemical composition often containing Mg, Ti and Mn mixed. Crystal axis, the Pentagon tetrahedral crystal class, mostly granular aggregates, dense block, often with magnetite illusion. Color and streak are brown, hardness, specific gravity 4.88, strong magnetic. Maghemite is formed by secondary changes in the role of magnetite under oxidizing conditions. Fe2 + in magnetite completely Fe3 + is replaced by (3Fe2 + → 2Fe3 +), so 1/3Fe2 + occupy the octahedral sites of vacancy. In addition, maghemite may be the lepidocrocite dehydration formed also by iron oxides formed by the organic role.
Limonite
Limonite (Limonite) of ore containing iron hydroxide, is generated by other mineral weathering, the most widely distributed in nature, but deposits buried a large amount of rare. It is collectively referred to as goethite (Goethite) HFeO2 and scales of iron ore (Lepidocrocite) FeO (OH) in two different structural ore, was also the main ingredients of the chemical formula written mFe2O3. nH2O, showing yellowish brown or brown, containing approximately 62% of Fe, O 27% H2O, 11%, the proportion of about 3.6 to 4.0, mostly attached to the existence of other iron ore. Actually not a mineral species, but goethite, lepidocrocite, water, goethite, water lepidocrocite, and moisture content of silica, shale and other mixtures. Most of the iron minerals limonite is 2Fe2O3 · H2O forms of existence. Chemical composition changes, the water content changes. The iron content of brown iron ore 37% to 55%, and sometimes phosphorus higher. Limonite of the absorbent, generally adsorbed with a lot of water to remove free water and crystal water in the roasting or into the blast furnace heat, thus increasing the porosity of ore, greatly improved the reduction of the ore. So the limonite more than the reduction of hematite and magnetite must be good. The same time, remove the moisture corresponding increase in the iron content of the ore.
(1) goethite α-FeO (OH), with Fe62.9%. Containing not quantitatively adsorbed water, said water goethite HFeO2 · NH2O. Orthorhombic form acicular, columnar, sheet-like or scaly. Usually showed a bean-shaped, kidney-shaped or bell emulsion. Cut mask parallel or radiation fibrous structure. Sometimes into a compact block, earthy, there was oolitic. Color reddish brown the Gampsocleis to dark brown. Weathering powder, ocher-like limonite was brown. The goethite streaks of reddish-brown, the hardness of 5 to 5.5, the proportion of 4 to 4.3. The limonite streak is usually pale brown or tan, hardness of 1 to 4, the proportion of 3.3 to 4.
(2) lepidocrocite γ-FeO (OH), containing Fe 62.9%. Containing not quantitatively adsorbed water, said water lepidocrocite FeO (OH) NH2O. Orthorhombic. Common scaly or fibrous aggregates. Color dark red to dark red. The streak of orange-red or brick red. Hardness of 4 to 5, the proportion of 4.01 to 4.1.
Siderite
Siderite (Siderite) containing carbonate of iron ore, the main ingredients of FeCO3, showing gray, 48.2% of the theoretical iron content, specific gravity of about 3.8. Of FeCO3, FeO 62.01%, 37.99% of CO2, often containing Mg and Mn. Trigonal system. Common rhombohedron, crystal faces are often curved. Aggregates into a coarse granular to fine granular. Also showed a nodular, botryoidal, earthy. Yellow, light brown (weathered dark brown), shiny glass. Hardness of 3.5 to 4.5, specific gravity 3.96, Mg and Mn content are subject to change. In nature, the industrial exploitation of the value of siderite is less than the other three ore. Siderite is easy to be decomposed oxidized to limonite. General iron content is not high, but after the thermal decomposition of CO2, not only the iron content significantly improve, but also to become porous, reducing good. This ore is mostly contain a considerable amount of calcium and magnesium salts. Carbonate will absorb a lot of heat at high temperature of about 800 ~ 960 ℃ and emit carbon dioxide, so most of the first blast furnace is then added to this type of ore to be calcined.
(5) other
Ilmenite (Ilmenite) its chemical formula is THERMODYNAMICS ON FeTiO3 and Fe 36.8%, Ti 36.6%, O 31.6%. Trigonal system. Rhombohedral class of the grain. Often has irregular granular, scaly or thick plate. Form a complete class of isomorphism in the ilmenite and hematite above 950 ℃. When the temperature decreases, the melting away, so ilmenite often contains small scaly hematite inclusions. The ilmenite color iron black or steel gray. Streak steel-gray or black. Showed brown or red streaks of brown with hematite inclusions. Metal - semi-metallic luster. Opaque, no cleavage. Hardness 5 to 6.5, the proportion of 4 to 5. Weakly magnetic. Ilmenite occurred mainly in the ultramafic rocks, mafic alkaline rock, acid rock, and metamorphic rocks. China's Panzhihua vanadium-titanium magnetite bed, ilmenite was directed granular or sheet distributed in the titanium magnetite and other mineral particles, or along the cracked surface of titanium magnetite into lamellae. Iron ore silicate (Silicate Iron) of such ores is a complex salt, the chemical formula, the ingredients vary widely, generally dark green, the proportion is about 3.8, very low iron content is a relatively poor iron ore. Pyrite (Sulphide iron) This ore contains FeS2, with Fe 46.6% while the S content of 53.4%. Showing greyish yellow, the specific gravity of about 4.95 ~ 5.10. Ore often contains many other more expensive metals such as copper (Copper), Ni (Nickel), Zn (Zinc), gold (Gold), Silver (Silver), etc., so often used as a metal smelting industry raw materials; and because it contains large amounts of sulfur, so often used to distill the sulfur, iron and have become the by-products, so the fact can not be called iron ore.