Mullite also called Cyanite, Disthene, Kaopolite, Kyanite is a high-quality refractory raw material, and this type of mineral is relatively rare. Mullite is a mineral produced by aluminosilicates at high temperatures. Mullite is formed when aluminosilicates are artificially heated. Natural mullite crystals are slender, needle-like and radially clustered. Mullite is used to produce high temperature refractories. Mostly used as thermal barrier coatings in C / C composites, it is widely used. The mullite AI2O3-SiO2 elementary system is a stable binary solid solution under normal pressure. The natural mullite with the chemical formula of AI2O3-SiO2 is very few. It is usually artificially synthesized by sintering or electrofusion.