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Case histories |
Mineralogy and Petrology Group, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
Kaolin is principally used as a white pigment in the manufacture of paper and whiteware ceramics and in paints, rubbers and plastics. The desirable properties of kaolin in these end uses include chemical purity, high kaolinite content, fine particle size, euhedral kaolinite platelets, high brighteness values and appropriate rheology. This paper outlines the laboratory evaluation of a kaolin from Chilulwe, near Serenje, Central Province of Zambia. The kaolin occurs in a hydrothermally-altered feldspar pegmatite within a granite-gneiss basement. Initial laboratory characterization of the kaolin showed it to consist mainly of microcline feldspar (80%) with 17% kaolinite and trace quantities of muscovite, beryl and tourmaline. A kaolinite concentrate, produced by wet screening and hydrocloning, contained 79–87% kaolinite, with a clay (< 2 µm) content of 58%, a brightness of 70–76% (86–870n firing) and a viscosity concentration of 68%. Transmission electron microscopy showed the kaolinite to consist of rolled and hexagonal crystals. The results of this study showed that the Chilulwe kaolin, and by-product K-feldspar, have potential as a raw material for manufacture of ceramic products.
