Minerals and Metals in Ancient India v1.c20.s3.t3: C. B&RW Culture Iron in the Eastern India
Minerals and Metals in Ancient India v1.c20.s3.t3
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C. B&RW Culture Iron in the Eastern India
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The chalcolithic traditions in (a) the Pre-, Mature-, and Post-Harappan (chapters 2-7), (b) Peninsular India (chapter 8) and (c) Eastern India (chapter 9) gradually gave rise to the Iron Age cultures in the respective areas. In chapter 9, we mentioned about the chalcolithic culture of Pāṇḍu Rājār Dhibi and the neighbouring areas of West Bengal and Bihar. This culture C-14 dated 1380 to 855 BC (Allchins, 1982: 261) spanned the period from the early chalcolithic to the advent of iron. The people there were in touch with the Copper Hoard tradition in the Doab and the Peninsular Chalcolithic tradition. In West Bengal and Bihar, endowed with high grade copper as well as iron ores, the Iron Age emerged from the chalcolithic period without any interruption; the well-dated period 1050-950 BC has been termed as ‘Ferro-chalcolithic’ by Chattopadhyaya and De (1989).
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The Black and Red Ware (B&RW) has very distinct local characteristics in the areas of Uttar Pradesh, Rajasthan and Central India. We are concerned with the B&RW culture of West Bengal and Bihar which clearly shows the advent of Iron Age during the period 1200-800 BC. (Chakrabarti, 1976, 1985)
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At the West Bengal site of Bahiri (Chakrabarti and Hasan, 1982) there is iron slag right on the natural soil C-14 dated 950 ± 150 BC. Hatikira village in Birbhum district has shown 1000 BC Iron Age culture. At Mahisadal in West Bengal, Iron Age starts right in the chalcolithic column dated around 800 BC. Iron slags, ingots and tools like arrowhead, point, spearhead have been obtained from the lowest chalcolithic strata Period I (1100 BC) of Mangalkot (in the Katwa sub-division of Burdwan district), 30 km south-east of Pāṇḍu Rājār Dhibi. (Ray, 1990) This shows that West Bengal acquired the knowledge of iron technology independently, and almost simultaneously as the PGW people of Atrañjikhera.
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At Barudih in Singhbhum, iron object has been found which occurs in an otherwise neolithic assemblage, characterised by a profusion of celts. Four radio-carbon dates have been obtained, the earliest being 1200 ± 210 BC (TF 1100). Chattopadhyaya and Ghosh (1982) have analysed a sample of carburized iron clearly showing the presence of pearlite, from coarse granular to lamellar, at places in equiaxed ferrite matrix. The normalized structure clearly shows that the implement was thoroughly forged and cooled slowly in air. We may recall that the iron samples from Atrañjikhera (chapter 11) of the same age also show carburization and pearlite structure.
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In chapter 9 we discussed the ferro-chalcolithic culture of Pāṇḍu Rājār Dhibi (1000-950 BC), a key site in the Ajoy Valley, district Burdwan, West Bengal. The site was excavated in 1964 and again in 1984-85. Specific C-14 dates have been obtained for the ferro-chalcolithic phase: 1012 ± 120 BC and 1045 ± 55 BC.
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Chattopadhyaya and De (1989) examined a dish-shaped iron object (length 62 mm, width 18 mm and thickness 2 mm) obtained from the ferro-chalcolithic phase of Pāṇḍu Rājār Dhibi. Observation of the specimen in computer automated electron probe micro-analyser (EPMA) revealed that the dish-shaped object was made of iron with a high amount of fayalite (iron silicate) inclusion which made it brittle. No carbide or pearlitic structure was detected. Although carburization did not take place, the presence of substantial amount of potassium in the inclusion indicated that the firing may have been done with charcoal.
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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)
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→ α Fe (iron) represents the successive stages of reduction, and the slag under consideration shows the results of the earliest efforts, only partly successful, to obtain iron from hematite, commonly available in the West Bengal-Bihar area.
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Matured Iron Age had existed around eighth century BC in Pāṇḍu Rājār Dhibi; the hardening and quenching methods were observed (Chattopadhyaya and De, 1989) in a third century BC sickle, which is so far one of the earliest Indian specimens exhibiting the steeling process. The length of the sickle is 255 mm and the maxium width 22 mm. The internal curved region of the agricultural tool has a sharp cutting edge. Chemical analysis revealed that it is a low carbon steel: carbon 0.22 per cent, copper 0.15, nickel 0.13, cobalt 0.11, rest iron. The metallographic structure shows that of tempered martensite. The structure also exhibits retained acicularity at certain places.
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Electron micrograph obtained at a magnification of 100 X clearly represents the tempered martensitic structure of the sample. Microhardness measurement showed a value of VHN 391 in the ferritic region, and 549 in the martensitic region. It is evident that the smiths of Pāṇḍu Rājār Dhibi, during third century BC, knew how to forge an iron sample at high temperature to exclude slag particles, how to carburize at red heat, then quench (quickly cool possibly in water), and then finally temper or reheat it to an intermediate temperature.
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Earlier, Chattopadhyaya (1984a) had studied a second century BC sample of iron razor from Ror, district Kangra, Himachal Pradesh which showed, apart from massive ferrite, martensite plates indicating the technique of rapid quenching. The Pāṇḍu Rājār Dhibi evidence of low carbon steel has pushed the Indian antiquity of quenched steel further back to third century BC. The Period III in Pāṇḍu Rājār Dhibi, which yielded the sickle, also exhibited a furnace probably for smelting iron and also one iron-smelting crucible.
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The Eastern tradition of smelting copper and iron continued well up to the Early Historic Period 450 BC-AD 400 (Chattopadhyaya and De, 1989: 33), and even beyond. The chronology of the traditions is yet to be fully discovered. At several stages, the industrial operations might have been conducted by special tribes.
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S.C. Ray discovered at Saradkel, 50 km from Ranchi and 9 km from Kunti, an Asura site of Iron Age settlement tentatively dated first-second century AD (Banerjee, 1965: 220-22 and Ghosh, 1989 Vol. 2: 393) A large number of iron objects such as arrowheads, axes with single or double cutting edges, chisels, nails, caltrops, knives and longitudinal ploughshares bespeak the prevalence of a full-fledged iron industry. Also found were hematitic ores, slags and sections of several vertical pits laid into the earth, one metre uniform width, 2-3 metre in depth, described as smelting furnaces. These present a contrast to the cylindrical or cubical clay-built shafts of the Agarias. The presence of punch-marked coin, beads of chalcedony, agate and carnelian, copper objects etc. suggest a complex of the Kuṣāṇa era. It is not clear how and when this Asura culture was replaced by the Muṇḍa tribes. The Muṇḍas continued making wrought iron which the Sanskritists called muṇḍaloha (the variety made by the Muṇḍas). The topic of tribal metallurgical practices, continued right up to the pre-British period, is beyond the purview of our discussion.
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West Bengal and Bihar definitely constituted one of the nuclear zones for the ancient metallurgical traditions in India. This zone contributed towards the emergence of the second urbanized culture (after the Harappan) and the political power in northern India during the Maurya-Gupta eras. Just as the north-western post-Harappan chalcolithic tradition was followed by the Iron Age in Rajasthan/Western Uttar Pradesh area, and the Copper Hoard and Eastern Chalcolithic traditions gave rise to Iron Age in East India, we witness the third nuclear zone in the Peninsular India where the iron-making tradition was rooted more in the neolithic rather than the chalcolithic era.