Explanatory notes
… oxide may contain small proportions of other oxides (e.g., titanium oxide, chromium oxide) either deriving from … the action of air and acids, and is very hard. It is used, e.g., as an abrasive, in the manufacture of refractory … in water, specific gravity about 3.7. Uses include, e.g., in aluminium metallurgy, as a filler for paints, in …