In Japan, kaolin is commonly referred to as porcelain clay or white pottery clay, while in England it is called china clay. In “Tian Kou Kaibutsu,” it is written, “This town (Jingdezhen) has been a place of pottery making from time immemorial to the present day. But it is not made of white clay. The clay comes from Wuyuan and Qimen Mountains. One is named Gaoliang Mountain. It is a hard clay. Its nature is hard. The first is called Kaixia Mountain. It produces glutinous rice soil. It is soft and soft. The clay is soft and glutinous, and the two are combined to form porcelain ware. The word kaolin seems to have come from Gaoliang (written as Gaoling in the Wuche Yinpu), where this white clay was produced, and was first seen in LeKaolin in an 18th-century letter by Dantrekor. Pure kaolin is composed of kaolinite with the formula Al2O3-2SiO2-2H2O.
The theoretical chemical composition is 46.51% silicate, 39.54% alumina, and 13.99% water, but in reality it contains not a few impurities such as mica, feldspar, and quartz. The refractoriness of pure kaolin is between 35 and 36 Zegel cones (1770-1790 degrees Celsius), but the presence of impurities significantly reduces this temperature. Kaolin is found in Devon and Cornwall, England; Saint-Irieu in Limoges, France; Meissen and Halle, Germany; Zetlitz near Karlovy Vary, Czech Republic; Illinois, North and South Carolina, Missouri, Utah, Texas, and California, USA; Jiangxi, Shandong Province, China and Hadong County, Gyeongsangnam-do, Korea are prominent.
Kaolinisation
The process by which a mineral is transformed into kaolin. There are five causes of kaolinisation
(i) Surface weathering.
(2) Lake water.
(iii) Groundwater containing carbon dioxide gas.
(4) Rising gases such as hydrofluoric acid, boric acid, and sulfuric acid from volcanic origin.
(V) Sulfuric acid and hydrogen sulfide solutions from oxidation of pyrite.
