Minerals and Metals in Ancient India v1.c27.s2.t2.6

v1.c27.s2.t2.6

The pillar was forge-welded from a great many sponge iron lumps of different composition, so that the elemental composition and the microstructure are variable from layer to layer. Micro-examination of unetched section of the pillar iron reveals slag particles distributed irregularly. In etched condition, polyhedral grains of ferrite with some slip bands in some grains near the surface are seen. Some ferrite grains have a small amount of pearlite at the grain boundaries. The slag content is high and this contains magnetite and FePO₄, seen as yellow specks on the surface.