In a sample of Red Mud, a by-product of the Bayer process, the reduction of ferric oxides to elemental iron and magnetite, performed prior to subjecting the sample to magnetic separation, was followed by thermogravimetric and differential thermal analysis (TGA/DTA) in an oxidizing atmosphere. The relative quantities of metallic iron and magnetite in the reduced sample can be estimated from the oxidation thermogram; in the case of the magnetic fraction, obtained via magnetic separation of the reduced sample, the absolute quantity of metallic iron and magnetite can be estimated from the relative thermogram.