Given there are many variations of mint (like peppermint and spearmint), many of these have specific magical properties on their own.
The medicinal qualities have already been covered, so I'll just cover the magical associations and uses.
The mint family as a whole is good for healing spells, prosperity spells, exorcisms and bringing good spirits in. I've personally heard that the spirit of mint is a small helpful personality with a coolness to it.
It was also considered to be special or sacred by the Druids supposedly.