Yes, SILICAS is a Scrabble word!

Letter values in Scrabble US: S 1, I 1, L 1, I 1, C 3, A 1, S 1.

Is it a valid word?

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

a white or colorless vitreous insoluble solid (SiO2); various forms occur widely in the earth's crust as quartz or cristobalite or tridymite or lechatelierite

Also: silicon oxide, silicon dioxide.