Kaolin-clay deposit in Iriki-machi, Kagoshima prefecture, has been made clear to consist of kaolin, montmorillonite and weakly altered zones and so on. Clay in the kaolin zone is called “Iriki kaolin-clay” and has not yet been used as a blending material for “white porcelain” because of high iron and titanium content.
The kaolin zone is largely classified into “pyrites zone” and “oxidized zone” depending upon whether the kaolin-clay includes pyrite or not. The measurement of mineralogical properties and the purification by a high gradient magnetic separator (HGMS) of the kaolin-clay belonging to “pyrites zone” were carried out in order to utilize it as a blending material for “white porcelain”. In the latter, the influence of dispersive state of the clay in slurries and the operating variables of HGMS on the yield and quality of the concentrate was studied.
The results obtained are summarized as follows. It was found that Iriki kaolin-clay mainly consists of kaolinite and quartz and also contains a little amount of dickite, pyrite and anatase and so on. The particle size of the clay was comparatively small and the cumulative weight percent of less than 2 μm was about 55.
2. When the clay was treated with HGMS, the effect of addition of dispersants on the yield and quality of the concentrate was clearly recognized but the influence of kind of dispersants was hardly found.
3. The pyrite mainly existing in coarser particle size range seemed to be easily removed in HGMS treatment while the titanium oxide being mostly contained in finer particle size region was rather difficult to be removed. It was also recognized in HGMS experiments that the iron and titanium content were decreased with decreasing the matrix loading and with increasing the intensity of magnetic field.
4. The whiteness of the clay treated with HGMS under the dispersive condition was made clear to be superior to that of the clay treated under the non-dispersive condition irrespective of heating up to 1300°C.
