Yes, GLASSWORT is a Scrabble word!

Letter values in Scrabble US: G 2, L 1, A 1, S 1, S 1, W 4, O 1, R 1, T 1.

Is it a valid word?

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

bushy plant of Old World salt marshes and sea beaches having prickly leaves; burned to produce a crude soda ash
fleshy maritime plant having fleshy stems with rudimentary scalelike leaves and small spikes of minute flowers; formerly used in making glass

Also: salsola kali, salsola soda, salicornia europaea.

Not playable in Scrabble US: KALI, KELPWORT.