Mint is an aromatic herb of which there are over 30 species, thetwo most popular and widely available being peppermint and spearmint.
Peppermint is the more pungent of the two. It has bright green leaves,purple-tinged stems and a peppery flavor.
Spearmint leaves are gray-green or true green and have a milderflavor and fragrance.
Source: The food lover's companion by S.T.Herbst.