Jaded is an adjective indicating that one is tired, bored, or lacking enthusiasm, usually because one has experienced an event or situation so many times that it no longer holds any interest.
This sense of 'jade' was originally used to refer to tired, overworked, and old horses, and was eventually generalized to humans. It is uncertain why horses were referred to as jaded, but it does not seem to have any relation to the semi-precious stone.