Yes, CRYSTALLIZATION is a Scrabble word!

Letter values in Scrabble US: C 3, R 1, Y 4, S 1, T 1, A 1, L 1, L 1, I 1, Z 10, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

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

the formation of crystals
a rock formed by the solidification of a substance; has regularly repeating internal structure; external plane faces
a mental synthesis that becomes fixed or concrete by a process resembling crystal formation

Not playable in Scrabble US: CRYSTALLISATION.