What is the difference between materialism and naturalism?

Naturalism says that all things that exist are natural, and the supernatural does not exist. Materialism agrees with that, but goes further by adding that all things that exist are matter, or a manifestation of matter (such as energy), or are reducible to matter.

Naturalism does not deny that certain things, such as the Mind, may not be reducible to matter. It merely denies that they are supernaturalistic. Materialism denies the possibility of all non-materialistic things altogether.