Yes, PATRIARCH is a Scrabble word!

Letter values in Scrabble US: P 3, A 1, T 1, R 1, I 1, A 1, R 1, C 3, H 4.

Is it a valid word?

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

title for the heads of the Eastern Orthodox Churches (in Istanbul and Alexandria and Moscow and Jerusalem)
the male head of family or tribe
any of the early biblical characters regarded as fathers of the human race
a man who is older and higher in rank than yourself