Gold jewelry refers to jewelry made of gold as the main raw material. The chemical symbol of gold is Au, with a specific gravity of 17.4 and a Mohs hardness of 2.5. Gold ornaments can be divided into pure gold and k gold according to their gold content. The gold content of pure gold jewelry is above 99%, and the highest can reach 99.99%, so it is also called "99 gold", "all gold" and "red gold".