The copper workings in India have an antiquity dating back to the second millennium BC. They are reported from Barudih in Singhbhum. We also have a small finger ring discovered at Babri, Birbhum, and West Bengal which has been formed from the chalcolithic levels and is dateable to about 1000 BC. It seems the copper mines at Chotanagpur plateau were in use at that point of time and tin as an alloy was being used to obtain bronze. In the Harappan culture copper tools were used to help cut stone tools in a finer manner.
The Harappans practiced alloying of copper and tin so that a more strong metal, bronze would be available. “Whereas 70 per cent of analysed copper artefacts from Mohenjodaro and Harappa have been found to contain one per cent tin (probably the same as found in the natural ore), the remaining 30 per cent had tin ranging from 8 to 12 per cent, which indicates that tin was here deliberately mixed with copper. The proportion of bronze within copper artefacts increases significantly with time at Mohenjodaro, and this was probably the case in the Indus Civilisation generally. Nickel, arsenic and lead were also used as copper alloys.
The ore for smelting copper in the Harappan culture was most likely obtained from Rajasthan and Baluchistan, though Afghanistan and Persian sources too would have made the supply “Copper was smelted in brick-lined pits, and wax-and-clay moulds were probably used to cast whole or parts of copper and bronze artefacts. These included tools such as razors, knives, chisels, hooks, sickles, saws and axes. Smaller copper tools include awls, nails, needles and tubular drills.
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A considerable number of copper and bronze utensils (pots and pans) suggest that at least richer households could now use metalware in addition to the breakable pottery”.
The Chalcolithic cultures, other than the Harappans, also used copper for making different artefacts. A content analysis of these artefacts reveals that the chalcolithic metallurgical traditions and the Harappan tradition had distinct identities and the probability of any direct transmission is precluded.
Iron:
The studies focusing on the history of introduction of iron in India had earlier believed that iron was introduced between 600 and 700 BC. But the discoveries made at Painted Greyware (PGW) sites have now settled this date around 1000 BC. D.K. Chakrabarti has written a comprehensive work dealing with the discovery and use of iron in India. Some of his main findings may be given here to understand the use pattern of iron:
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i. The probable date of production of iron in India is 800 BC;
ii. The use of iron in India is earliest reported from Central India and South India;
iii. These production centres were located close to the areas from where ore was found;
iv. There was a continuity in tradition of iron metallurgy upto the preindustrial period; and
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v. Any correspondence between the Indian iron tools of the earliest period and the West Asian tools was lacking.
Zinc:
India provides the earliest evidence of metallic zine. “There are references to burning a metal, rasa, to produce an eye salve, which should refer to zinc, placing it use in the last centuries of the first millennium BC. The Rasaratnakara, ascribed to Nagarjuna, the great Indian scientist who lived in the fourth century AD, describes both the production of brass by the familiar cementation process, and of metallic zinc. Furnaces (Koshthi) have been found at the ancient mines of Zawar in Rajasthan. The Zawar mines from where zinc was extracted are located at about 35 kms. To the south of Udaipur in Rajasthan. The ore is mainly a mixture of zinc and lead and is obtained in dolomite formations. Agarwal suggests that “zinc and some lead were being mined between the sixth and first centuries BC”.
This trend then continued further and as we come to medieval India we find evidence of zinc distillation process on a fairly elabourate scale. P.T. Craddock specialises in the study.
We give an extract from him explaining the process (as quoted in Aggarwal): “at first glance the Zawar industry is the most unusual phenomena, a fully fledged technology with neither antecedents nor successors and apparently no contemporaries either, for even within India it seems unique. Zinc required a much higher temperature and the total exclusion of air.
The form of the Kosthi furnace for holding the retorts seems to have been inspired by the common spottery kiln. The arrangement is of course totally different, instead of a fire beneath to heat the pots stacked above through the perforated floor, in the Kosthi, the fire and retorts were in the upper chamber and the zinc was collected beneath the Zawar process was certainly one of the most sophisticated and technically exacting process developed in the mediaeval world, one hesitates to use the term ‘pre-industrial’, for surely this process, with its appreciation of scientific techniques and learning towards mass production, should properly be considered as an early example of an industrial process in the modern sense”.