However, this is not the case. There are several reasons for discoloration of gold jewelry, such as metallic abrasion and corrosion , and they can sometimes be prevented with some general care .
Cosmetics often contain compounds harder than the jewelry itself.
These compounds wear or rub off very tiny particles of the precious metals. Very finely divided metal always appears black, rather than metallic, so it looks like a jet-black dust. When this dust comes into contact with absorbent surfaces such as skin or clothing, it sticks, forming a black smudge. To prevent this, you should try switching cosmetics. If this is not possible, we recommend that you remove your rings and other jewelry while applying your makeup, and then clean the skin areas which will be in contact with the jewelry with soap and water before putting the jewelry on.