How to identify K9 material crystal lamp K9 crystal is also called K9 glass, can also refer to glass products made of K9 material, used for optical coating and other fields, the price of 10-15 yuan per kilogram (only for reference, the actual according to different levels have a certain big difference). The transmittance, refractive effect, hardness and texture are far higher than resin material. The main molding is cutting polishing and polishing and pressure casting (need furnace). K9 material belongs to optical glass, crystal clear, so derived a lot of K9 material as the processing object of the factory, they process the products, known as crystal glass products in the market.