Copper-silver alloy. According to relevant public information, it is made up of two inorganic copper preparations. It is not simply copper hydroxide and king copper, but a special preparation method in which king copper wraps copper hydroxide. Divalent copper salt is the most common copper compound. Its hydrated ions often appear blue, while chlorine as a ligand appears green. It is the source of the color of minerals such as azurite and turquoise. It has been widely used as a pigment in history. Copper Patina (basic copper carbonate) will be produced when the material building structure is corroded. Decorative art mainly uses metallic copper and copper-containing pigments.