Yes, ISINGLASSES is a Scrabble word!

Letter values in Scrabble US: I 1, S 1, I 1, N 1, G 2, L 1, A 1, S 1, S 1, E 1, S 1.

Is it a valid word?

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

any of various minerals consisting of hydrous silicates of aluminum or potassium etc. that crystallize in forms that allow perfect cleavage into very thin leaves; used as dielectrics because of their resistance to electricity