Yes, MOHAWK is a Scrabble word!

Letter values in Scrabble US: M 3, O 1, H 4, A 1, W 4, K 5.

Is it a valid word?

MOHAWK is a valid word in the official Scrabble dictionary (US) and the UK Scrabble Dictionary, but not in Words with Friends (ENABLE).

a member of the Iroquoian people formerly living along the Mohawk River in New York State
the Iroquoian language spoken by the Mohawk
haircut in which the head is shaved except for a band of hair down the middle of the scalp

Also: mohawk haircut.