Yes, ZIRCONIUM is a Scrabble word!

Letter values in Scrabble US: Z 10, I 1, R 1, C 3, O 1, N 1, I 1, U 1, M 3.

Is it a valid word?

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

a lustrous grey strong metallic element resembling titanium; it is used in nuclear reactors as a neutron absorber; it occurs in baddeleyite but is obtained chiefly from zircon

Also: atomic number 40.

Not playable in Scrabble US: ZR.