FANG Yesen , FANG Jinman

(Department of Geology, Nanjing Univer sity)

Abstract:Porcelain-grade Kaolin is widely distributed in China, and has a long history of exploitation and utilization. It occurs mainly in Suzhou, Jiepai, Daton, Chaozhou, and J ingdezhen. Resear ch on the porcelain Kaolin of China in the past years shows that most of the Kaolins in the North China are of sedimentary type, and that the ore deposits of Kaolin occur in the coal-bearing strata of Paleozoic and Mesozo ic age. The origin of Kaolins in the South China is related to acid igneous rocks, such as granite etc, and most of them belong to weathering (residual) types, or to hydrothermal alteration types. The different geological conditions of or formation have resu­lted in a variation in mineral and chemical composition of the Kaolin, as woll as to difference in technological properties. The Chemical composition of Kaolin in Suzhou is close to the stoic­hiometrlc formula for standard Kaolinite. Its main mineral co mponents are Kaolinite, 7A halloysite and l0A halloysite. It has high plarticity and bonding proporties, and has high whiteness and refractoriness after burning. So it becomes an important raw material in the porcelain industry. The chemical composition of Kaolin in J iopai is characterized by high SiO₂ , low Al₂O₃ and Fe₂O₃, and little Na₂O and K₂O.It is mainly composed of poorly crystallized Kaolinite, 7A halloysite, muscovite, quartz and albite etc. It has a fine grain size and shows high whiteness and refractoriness after burning, and shrinkage is low. So it is a high-guality raw mateial preferred for the manufacture of fine porcelain table­-wares. The chemical composition of Kaolin in Datong is similar to the composition of Suzhou kaolin. Its main mineral component is Kaolinite. Owing to the presence of an organic matter impurity. The Datang Kaolin has high plasticity and better shaping propertie, after ball-milling. The Kaolin in Feitienyan (Chaozhou) -has high SiO₂ , low Al₂O₃ and the K₂O is higher than in other Kaolin.Its principal minerals are illite and Kaolinite. It has moderate plasti­city, and whiteness can rise to 70一80% reflectivity after birning. So it can be used directly in manufacturing porcelain. The chemical composition of Kaolin in Jingdezhen is characterized by high SiO₂ and Fe₂O₃, low Al₂O₃. After washing Al₂O₃ can increase to 34一36%. Its main minerals are Kaolinite and 7A halloysite.

Keywords:  Porcelain-grade Kaolin, muscovite