The basic principle of vacuum coating of crystal is: in the vacuum chamber, the plating material (titanium and other metals or alloys) is melted and evaporated to generate plasma by using the large energy of arc discharge, and then accelerated by electric field and reacted with reaction gas to form metal compounds (such as tin), and finally deposited on the surface of crystal workpiece. The crystal surface can have different colors after coating. The surface is wear-resistant and scratch resistant. The crystal pendant on the lamp and the small diamond all adopt vacuum coating technology