Hydrogen sulfide gas in the air causes silver jewelry to tarnish. This process happens quickly when silver jewelry is left out in the open, unprotected by a jewelry box. Tarnished silver jewelry turns a person's skin black or green when it is worn.
Frequently wearing silver jewelry prevents it from tarnishing. When silver jewelry is worn, it is protected by the oils in human skin. Prevent tarnishing by polishing silver jewelry on a regular basis, and keeping it out of the open air. Silver jewelry should be stored in a box to prevent tarnishing. Silver jewelry should be removed when working with chemicals or cleaning solutions.