Yes, PEPPERMINT is a Scrabble word!

Letter values in Scrabble US: P 3, E 1, P 3, P 3, E 1, R 1, M 3, I 1, N 1, T 1.

Is it a valid word?

PEPPERMINT is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

herb with downy leaves and small purple or white flowers that yields a pungent oil used as a flavoring
red gum tree of Tasmania
a candy flavored with peppermint oil

Also: mentha piperita, red gum, peppermint gum, eucalyptus amygdalina, peppermint candy.