Yes, STELLITES is a Scrabble word!

Letter values in Scrabble US: S 1, T 1, E 1, L 1, L 1, I 1, T 1, E 1, S 1.

Is it a valid word?

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

a very hard alloy of cobalt and chromium with cobalt as the principal ingredient; used to make cutting tools and for surfaces subject to heavy wear