Minerals and Metals in Ancient India v1.c20.s3.t3.7

v1.c20.s3.t3.7

The slag found in the chalcolithic level (1250-1050 BC) of the above-mentioned site contained 34 per cent magnetite, 6 per cent wüstite, 48 per cent fayalite, 7 per cent anorthite (calcium aluminium silicate) and 5 per cent glass phase. The microstructure reveals that dendritic wüstite (lighter) phase occurs in a fayalite matrix. This kind of slag is similar to ‘Type A’ as described by Tylecote and Wynne. The substantial amounts of slag inclusion in the metal, and high proportions of unreduced oxides in the slag (a few slag samples were strongly magnetic and had 50 per cent magnetite) suggest that smelting could have been conducted below 1100°C. Traces of alpha-iron and hematite (altered from magnetite) were also noticed. Chattopadhyaya and De (1989) suggested that the original charge could have been magnetite ore; however, this need not have been the case. The sequence Fe₂O₃ (hematite) → Fe₃O₄ (magnetite) → FeO (wüstite)