zirconium dioxide, ZrO, a white, infusible powder used in making crucibles, furnace linings, pigments, etc. and, because of its luminosity, in incandescent burners
See zirconium oxide in American Heritage Dictionary 4
noun
A hard white amorphous powder, ZrO2, derived from zirconium and also found naturally, used chiefly in pigments, refractories, and ceramics and as an abrasive.