Flint Clay is a representative of high-quality hard clay in my country. It generally refers to cooked flint Clay, which is formed by calcining kaolin ore at high temperature. The Al₂O₃ content of the calcined flint Clay is more than 45%, Fe₂O₃ is less than 0.6%, the body density is about 2.55g/cm², the porosity is about 3.5, and the mullite phase content is about 60%. The refractoriness is greater than 1750℃. It has stable composition, uniform texture, dense structure, and white shell-like cross section.