Haematite. This mineral ore (iron oxide, formula: Fe2O3) is mined as the principal source of the metallic element iron. Kidney ore, the botryoidal (grape-like) form of haematite, is seen at centre right. Here it is a dull red, though haematite's colour can vary from black to steel grey. It is a common and widely-distributed mineral with industrial uses in paint manufacture (as a red pigment) and in polishing compounds.