Type and property of iron minerals

There are many kinds of iron minerals, while more than 300 kinds of iron minerals are found so far. Among them, there are 170 kinds of iron mineral are common. However, the iron minerals with utilization value in industry mainly include magnetite, hematite, limonite, siderite, ilmenite and pyrite in the current technical conditions.

1. Magnetite: Magnetite is a mineral, one of the three common naturally occurring iron oxides (chemical formula Fe3O4) and a magma cause of formation,which is formed in function and metamorphism process. The chemical structure of magnetite, Fe3O4, the mass fraction of FeO in magnetite is 31.03% and Fe2O3 68.97%, while the theoretical chemistry composition is 72.4% for Fe and 27.6% for O. Aggregation is generally compact mass and granularity, with a ironish black color, a black strip, semi metallic luster and opaque. Moh’s hardness is 5.5-6.5, with a density of 4.9-5.2g/cm3 and strong magnetism. After oxidation, magnetite becomes hematite, but can still maintain the original crystal, which is known as the false hematite or semi false hematite.

2. Hematite: in nature, there are two kinds of homogeneous variants of Fe2O3, namely Fe₂O₃ and Fe₂O₃. The former is stable under natural conditions, known as hematite. The latter is less stable than the former, known as magnetic hematite.

3. Ordinary hematite: theoretical chemistry of ordinary hematite is composed of Fe 69.94%, O 30.06%. Crystalline hematite is just gray and  crystal, while earthy hematite is red, with a cherry red or fresh pork liver strip. Mohs hardness is 5-6, with metallic and semi metallic luster, density of 5-5.3g/cm³ and weak magnetic.

4. Maghemite: The chemical formula of the magnetic hematite is 2-Fe2O3, always with the granular aggregate, dense block, often with false appearance of magnetite. Color and streak are brown, Moh’s hardness is 5, with brown color and strip, density of 4.88g/cm³ and strong magnetic.

5. Limonite: limonite refers to hydrous ferric oxide ore, is generated by the other ore after weathering. Its chemical composition changes greatly, and the change of water content is also large.

6. Siderite: The chemical formula of siderite is the FeCO3, the chemical composition of the is FeO62.01%, CO237.99%, Mg and Mn. Yellow, light brown yellow (dark brown), glass luster. Moh’s hardness is 3.5－4.5, with density of 3.96g/cm³ , varying according to the contents of Mg and Mn.