This lecture covers the metallurgy of precious metals, focusing on silver and gold alloys. It discusses the effects of oxygen on silver, methods to prevent tarnishing, and the oligodynamic effect of silver. The lecture also explores the color properties of gold alloys, the ternary system of Au-Cu-Ag, and the requirements for precious metals in jewelry. Additionally, it delves into the hardening mechanisms in Au-Cu alloys, the color tuning of gold alloys, and the metallurgy of platinum alloys, highlighting their hallmarking standards and alloying elements.