Gold and platinum are among the word’s most tarnish-resistant metals.
Then why is it that sometimes the gold jewelry leaves a black smudge on the skin? What is going on? Actually, it is not the gold that leaves that black smudge. It is the skin’s oil and cosmetics reacting with the gold alloys. What is the solution? Simple: clean your jewelry often and switch the brand of your lotion and cosmetics.
Silver does tarnish because it reacts to particles in the air (sulphur, in particular). This tarnish is a micro-thin coating and not deterioration of silver, and can be easily wiped away. Higher end silver jewelry is coated with a tarnish-resistant thin layer of rhodium which prevents silver from tarnishing.