Yes, LITHOGRAPH is a Scrabble word!

Letter values in Scrabble US: L 1, I 1, T 1, H 4, O 1, G 2, R 1, A 1, P 3, H 4.

Is it a valid word?

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

a print produced by lithography
duplicator that prints by lithography; a flat surface (of stone or metal) is treated to absorb or repel ink in the desired pattern

Also: lithograph machine.