Pure silicon carbide is a colorless and transparent crystal. Industrial silicon carbide is light yellow, green, blue and even black due to different types and contents of impurities, and its transparency varies with its purity. SiC crystal structure is divided into hexagonal or rhombohedral α- SiC and cube β- SiC (cubic silicon carbide). α- Because of the different stacking sequences of carbon and silicon atoms in its crystal structure, SiC has formed many different variants, and more than 70 kinds have been found. β- SiC transforms into α- SiC。 The industrial process of silicon carbide is to use high-quality quartz sand and petroleum coke to refine in a resistance furnace. The refined silicon carbide block is made into products of various sizes through crushing, acid and alkali washing, magnetic separation, screening or water separation.