Iron ore refers to ore with useful value, containing iron elements or iron compounds, and is almost only used as raw materials for steel production. Steel is the pillar industry of the national economy, and iron ore is the most important raw material for steel production. It takes about 1.6 tons of iron ore to produce 1 ton of pig iron, and iron ore accounts for more than 60% of the cost of pig iron. It can be seen that iron ore stone is also an important raw material closely related to the national economy.

Iron ore

According to the composition of iron-bearing minerals, iron ores can be mainly divided into 4 categories: magnetite, hematite, limonite and siderite. Various iron ores have different external morphology and physical properties due to their different chemical compositions, crystalline structures, and the geological conditions in which they are formed.

4 Types of iron ore

Magnetite

The main iron-bearing mineral is magnetite, and its chemical formula is Fe3O4, of which FeO=31%, Fe2O3=69%, and the theoretical iron content is 72.4%. This ore sometimes contains a combination of TiO2 and V2O5 composite ore, called titanomagnetite or vitriolite respectively. Magnetite has strong magnetic properties, and the crystals are often octahedral, and a few are rhombic dodecahedrons. The aggregates often form dense blocks, the color streaks are iron black, semi-metallic luster, the relative density is 4.9-5.2, the hardness is 5.5-6, and there is no cleavage. The gangue is mainly quartz and silicate. It has poor reducibility and generally contains high levels of harmful impurities such as sulfur and phosphorus.

Magnetite

Structure:

Appearance is black gray with metallic luster, black streaks, commonly known as "green ore", magnetite is generally very hard.

Distribution range:

It is mainly distributed in Shandong, Hebei, Henan, Liaoning and other regions. The most prominent feature of this ore is its magnetic properties.

Uses:

Magnetite is not only the main mineral raw material for iron smelting, but also one of the traditional Chinese medicinal materials. Traditional Chinese medicine believes that it has the effect of calming the mind; many magnetite is also accompanied by elements such as titanium, vanadium, and chromium. It can be used comprehensively, and magnetism has important applications in modern medicine, such as nuclear magnetic resonance imaging technology.

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Hematite

Hematite is anhydrous iron oxide ore, its chemical formula is Fe2O3, and the theoretical iron content is 70%. This ore often forms huge deposits in nature, and it is the main ore for industrial production in terms of burial and mining volume. The iron content of hematite is generally 50% to 60%, and it contains less harmful impurities such as sulfur and phosphorus, and the reduction is better than that of magnetite. Therefore, hematite is an excellent iron-making raw material.

Hematite

Structure:

Hematite crystals vary, from very close to very dispersed and very soft powder, so the hardness is also different, the general hardness is 5~6.

Hematite ore is abundant in China, and it is one of the main sources of iron ore. There are only a few places where hematite has perfect metal flashing rhombohedral crystals. In more cases, the crystals are often flat.

Distribution range:

Hematite is widely distributed. Hematite can be generated in many cases, but the most important hematite is sedimentary, and hematite is often produced together with magnetite.

Uses:

In addition to iron making, powdered hematite is also used as a red pigment and abrasive.

Medicinal hematite can also calm the liver and subdue yang, repress the inversion, cool blood and stop bleeding.

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Limonite

Limonite is a hydrous iron oxide ore, which is formed after the weathering of other ores, and is the most widely distributed in nature, but it is rare to find a large amount of ore deposits. Its chemical formula is nFe2O3·mH2O (n=1~3, m=1~4). Limonite is actually a mixture of goethite (Fe2O3·H2O), hydrogoethite (2Fe2O3·H2O) and iron oxides with different crystal waters and argillaceous substances. Most of the iron-bearing minerals in limonite exist in the form of 2Fe2O3·H2O.

Generally, the iron content of limonite is 37% to 55%, and sometimes the phosphorus content is higher. Limonite has strong water absorption, and generally absorbs a large amount of water. After roasting or heating in a blast furnace, free water and crystal water are removed, and the porosity of the ore increases, which greatly improves the reducibility of the ore. Therefore, the reducibility of limonite is better than that of hematite and magnetite. At the same time, the iron content of the ore is correspondingly increased due to the removal of moisture.

Structure:

Because limonite is weathered from other iron ores, its structure is relatively soft, its specific gravity is small, and its water content is large. Limonite has different colors due to different crystalline content, from yellowish brown to dark brown or dark gray.

Distribution range:

Limonite is the most widely distributed in nature, but it is rare to find large deposits. The world famous mining areas are Lorraine in France, Bavaria in Germany, Sweden and other places. There is no large buried limonite in China.

Uses:

The crystal water of limonite is easy to remove when it is dry. Limonite has many pores and is easy to reduce. Although its iron content is lower than that of magnetite and hematite, it is relatively loose and easy to smelt. So it is also an important iron ore.

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Siderite

Siderite is carbonate iron ore with a chemical formula of FeCO3 and a theoretical iron content of 48.2%. In nature, siderite is less valuable for industrial mining than the other three ores. Siderite is easily decomposed and oxidized to limonite. Generally, the iron content is not high, but after the carbon dioxide is decomposed by heating, the iron content increases significantly and becomes porous, and the reducibility is better.

Siderite

Structure:

The exterior color is generally gray-white or yellow-white, and can become brown or brown-black after weathering.

Distribution range:

It is mainly distributed in the western region, and the reserves of siderite in five provinces including Xinjiang, Qinghai, Gansu, Shaanxi and Yunnan all exceed 100 million tons.

China's siderite resources are very rich. At present, the known reserves are nearly 2 billion tons, and the remaining reserves are nearly 2 billion tons.

Uses:

When there are few impurities in siderite, it can be used as iron ore to extract iron; natural pure siderite can also be used to develop magnetic daily-use ceramics, which is the first time at home and abroad.

ceramics

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