Clay (also known as "Kaolin") - Clay (H4Al2Si2O9) is the main raw material of ceramics. It is produced in the world near the kilns of Jingdezhen in China named after the kaolinite. Evolved from "kaolinite" the Chinese word for "Kaolin", and became an international term. Pure clay is a white or gray, with silk-like luster of soft mineral. Clay metamorphic mica and feldspar, which are sodium, potassium, calcium, iron and other loss, coupled with the change from the water, this effect is called "china clay" or "kaolin-based." As for the clay of what is causing, in academia, although not yet conclusive, but can be considered roughly feldspar due to the gas or water and marsh plants spa corruption when containing carbonated act born of metamorphism. Usually clay prolific in the vicinity around the spa or lime layer, may be the reason. Clay melting point is about 1780 ℃, in fact, because how many contain impurities, so it's slightly lower melting point