Magnetic characteristics of several natural hematite and synthetic ones were investigated from the viewpoint of iron are processing by high gradient magnetic separation. Results obtained are as follows.
Ferrimagnetic minerals such as magnetite or maghemite, the discrimination of which was not necessarily easy, were usually contained in natural hematite ores. Though the greater part of ferrimagnetic minerals could be separated from hematite by the magnetic separation of finely ground are in low magnetic field, very small amount of ferrimagnetic minerals still remained in non magnetic products. As a result, -regional difference in magnetization of natural hematite was observed due to the difference of the amount of unseparated ferrimagnetic minerals in hematite. The characteristics of magnetization curves for used natural hematite samples show that of parasitic magnetism in appearence. But the values of spontaneous magnetization component differ by the place of sample production, which means that the ferrimagnetic minerals, are included in hematite of parasitic magnetism. After oxidizing the natural hematite samples by heating at 800°C in an air, the components of spontaneous magnetizations of natural hematites from different areas settled in the standard value of about 2×10
-5 emu/g. The temperature dependence of magnetization was also measured on the oxidized hematite in the range of -200 to 700°C which covers the Morin temperature and Curie temperature, refering that of pure synthetic hematite samples.
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