Yes, MADEIRAS is a Scrabble word!

Letter values in Scrabble US: M 3, A 1, D 2, E 1, I 1, R 1, A 1, S 1.

Is it a valid word?

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

a group of volcanic islands in the Atlantic Ocean to the west of Morocco; the group forms an autonomous region of Portugal
a Brazilian river; tributary of the Amazon River
an island in the Atlantic Ocean off the coast of Africa; the largest of the Madeira Islands
an amber dessert wine from the Madeira Islands

Also: madeira islands, madeira river.