Ancient iron making process at Naikund, Vidarbha region of India: a thermochemical analysis of megalithic iron smelting

This study systematically demonstrates the ancient iron-making process in one of the earliest iron-smelting sites in India, and Naikund, Vidarbha region, dating as far back as 900 bc. During the process, the maximum temperature attained in the Naikund furnace was estimated to be ~1150–1250°C in the reaction zones where solid-state reduction of iron followed by separation of the low-melting slag phase and metallic iron were predominant. The low melting point of the slag phase is possibly due to the addition of sand or silica and limestone in the furnace during the iron-making process. Furthermore, mass balance studies performed using the Rist diagram superimposed with the Fe–C–O stability diagram revealed that the minimum charcoal rate was about 1900 kg/tonnes of iron produced. It can be anticipated that the porous, semi-solid metallic iron is hammered to produce various objects used for hunting and agriculture. The thermochemical analysis of one of the earliest iron-smelting sites in India provides evidence of the ancient iron-making processes in the country. This study further opens up multitudes of possibilities to analyse ancient metallurgical structures in India