Minerals and Metals in Ancient India v1.c27.s2.t2.18

v1.c27.s2.t2.18

The apparent rustlessness of the Delhi pillar has been investigated by several scholars. (Hadfield, 1912, 1922, 1925; Ghosh, 1963; Lahiri et al., 1963; Bardgett and Stanners, 1963; Wranglén, 1970) The part of the pillar which is below ground is covered by a rust layer, about 1 cm thick, and shows deep pitting. Above ground, the pillar is coated by a protective film, 50-500 µm thick, analysed by Ghosh (1963) as: 67.0 per cent Fe₃O₄, 13.1 per cent FeO, 14.8 per cent H₂O, 1.7 per cent FePO₄, 3.1 per cent SiO₂, 0.2 per cent MgO and 0.1 per cent CaO.