<Original Papers>Ore Dressing Investigations of Titaniferous Iron Placers. (V) : A Few Mineralogical Properties of Alluvial Iron Placers from the Tohoku District

A few mineralogical properties of the products from the low-intensity magnetic separation of the titaniferous iron placers from Misawa, Sabishiro, Shinchi, Takachiho, Odaka, and Fukura were examined by means of differential thermal analvsis, spectral reflectance measurement, X-ray diffraction analysis, and microscopic identification. At the same time, the above-mentioned properties of pure magnetite, specularite, ilmenite, and quartz were investigated, and compared with those of the former samples for reference. The thermal curves of the magnetic concentrates were similar to one another in shape, but somewhat different from the curve of pure magnetite. The exothermic peak of ilmenite in the magnetic tailings was found at a higher temperature than that of pure ilmenite. The relation between the luminosity and the Fe-content of the products separated magnetically was expressed in a curve which resembles an exponential curve connecting the points corresponding to magnetite and quartz. It was observed under the microscope that a part of TiO_2 in the magnetic concentrates was in the form of free particles of Fe_2O_3-ilmenite, the larger part of TiO_2 being in the form of solid solution with magnetite, and that the most part of TiO_2 in the magnetic tailings existed in the form of free particles of Fe_2O_3-ilmenite. The value of TiO_2/T.Fe of raw ore was an important criterion for the grade and recovery obtainable in the separation of titanium concentrates from magnetic tailings. In addition to the above experiments, the thermal analysis curve of specularite was precisely determined, and it was found that the thermal curve dropped stepwise at 360℃ and 550℃ in the endothermic direction and suddenly rose at 675℃, corresponding to the Curie point of specularite, in the exothermic direction with steady rise in temperature