Haematite. This mineral ore (iron oxide, formula: Fe2O3) is mined as the principal source of the metallic element iron. This sample has been partially polished, removing most of the red oxide coating (rust) that forms upon exposure to air. Other forms of haematite can be red or brown in colour. It is a common and widely-distributed mineral with industrial uses in paint manufacture (as a red pigment) and in polishing compounds.