Minerals and Metals in Ancient India v1.c20.s3.t5: Early Iron Age in the Hallur Area
Minerals and Metals in Ancient India v1.c20.s3.t5
- Language
- English
Early Iron Age in the Hallur Area
v1.c20.s3.t5.1
Hallur is in the district of Dharwar on the left bank of Tungabhadra, anciently known as Hallavaru. In this area, the Neolithic Period I (1710-1030-100 BC) overlapped with Iron Age starting around 1200-1100 BC with a very short iron-free chalcolithic period. The megalithic iron age was characterised by typical B&RW, varieties of iron tools, megalithic cairns and cists, bone, carnelian, terracotta, gold, green stone and antler beads. (Nagaraja Rao, 1971 and 1981)
v1.c20.s3.t5.2
The Hallur area provides one of the three earliest dates for Iron Age Culture in India (Atrañjikhera and Pāṇḍu Rājār Dhibi in North India providing the other two). In chapter 10, we referred to some of the ancient mines of copper in the Karnataka area which must have witnessed very early open cast iron ore mining also. We would like to record the technical details of a few iron objects found from Komaranhalli and Tadakanhalli. Komaranhalli is one of the important megalithic burial sites 12 km east of Hallur dated 1200-1100 BC by thermoluminescence determination. (Indian Archaeology — A Review 1980-81, Archaeological Survey of India, New Delhi, 1983, p. 29) Tadakanhalli is the megalithic site dated 1000 BC, near (and contemporary to) Hallur site. (Nagaraja Rao, 1981: 25) The National Research Laboratory for Conservation of Cultural Property (NRLCCP), Lucknow, India received 31 objects from Komaranhalli (arrowheads, axes, knives, daggers, swords, spearheads, bars and rods etc.) and 20 from Tadakanhalli (above types and also chisels) for metallographic examination. Several samples were found to be heavily corroded; investigations were carried out on the rest which had some residual metal. (Agrawal, O.P., 1980-81 and 1990) A Komaranhalli spear and an axe from Tadakanhalli were examined with great detail, the results of which are presented below.
v1.c20.s3.t5.3
Both the specimens revealed laminated structure. Two sections were drawn from the blade and stem portion of the Komaranhalli spear measuring 178 cm in length and 3 cm in breadth. The blade showed a small metal core (the rest corroded) in three layers, two carburized and one uncarburized iron. While the light-coloured layer was ferritic and had low carbon (0.05%) and low hardness (HV 105), the darker carburized layer was of hypoeutectoid steel with dispersed pearlitic structure and had higher carbon content (0.2 to 0.24%) and higher microhardness. (HV 125-35) The section from the stem also revealed an air cooled dispersed pearlitic structure. Agrawal *et al.* (1990) concluded that the spear must have been prepared by hammering and welding together the sheets of carburized iron. The blade of the spear after receiving the final shaping at high temperature was also worked below the critical temperature 730°C and cooled in air. There is no evidence of hardening. The examination of other artefacts from Komaranhalli (1200-1100 BC) such as spearheads, daggers and swords also showed the evidence of lamination technique.
v1.c20.s3.t5.4
Similarly the cutting edge of the Tadakanhalli axe revealed a banded structure caused by three carburized and pearlitic layers (hardness HV 120-130 and carbon 0.2-0.3 per cent) and four uncarburized and ferritic layers (HV 98-109 and carbon 0.04-0.05 per cent). A close examination of the ferritic microstructure in the uncarburized layer indicated that the diffusion of carbon was only along the grain boundaries. This probably took place around 700-800°C. The deformed state of the lamellar pearlitic structure suggests that the axe was forged below the critical temperature (around 650°C) and cooled in air. In their first communication, Agrawal *et al.* (1980-81: 99) claimed the presence of bainite and martensite in the Tadakanhalli axe which was suggestive of quench-hardening. But Chattopadhyaya (1984b: 364) pointed out that “from the published photomicrograph nothing can be ascertained about the presence of martensite or bainite”. Subsequently, Agrawal *et al.* also agreed (1990: 15) that ‘there is no indication of the Tadakanhalli axe having been hardened and tempered’.
v1.c20.s3.t5.5
Nevertheless, Agrawal *et al.* have proven beyond doubt that the metalsmiths of the megalithic period (1200-1000 BC) introduced in India the lamination (layering or faggoting) technique in which two sheets of iron were welded and forged together. One sheet was carburized and the other was not. In this way several sheets of iron and carburized iron could be piled alternately and forged into a flat slab having requisite ductility (of wrought iron) as well as hardness (of carburized iron). Later on these piles could be heated, hammered and folded during the fabrication of the artefacts. Agrawal *et al.* showed that the laminated samples examined had (a) clearly visible welding joints, (b) continuous chain of slag inclusions, (c) sudden changes in concentration of carbon, and (d) sudden changes in the orientation of elongated slag inclusions. These evidences confirm that lamination had indeed been done.
v1.c20.s3.t5.6
Earlier in this chapter, we have quoted Maddin *et al.* (1977) reporting ‘the earliest known laminated iron object’ which is an Egyptian knife dated 900-800
v1.c20.s3.t5.7
BC. This date is much later than that of the Hallur site laminated weapons and we believe that it is quite possible that the technology diffused westward from India.
v1.c20.s3.t5.8
Agrawal et al. (1990) further showed that the lamination techniques was in vogue in India 1200 BC-AD 600. This is evident from the diversity of samples from Jājamau (600 BC-AD 600), Hulaskhera (700 BC-AD 700), Sringverpura (250 BC-AD 200), Kauśāmbī, PGW AD 500 etc. which were examined by them.
v1.c20.s3.t5.9
Jājamau (near Kanpur city) yielded 210 iron artefacts. Many of them were laminated structures. The cutting edge of an iron axe had a low carbon layer (0.2-0.24% carbon) sandwiched by two high carbon layers having carbon content as high as 0.6-0.65 per cent in some places. The low carbon layer had hardness HV 125 and the high carbon layer HV 267. The latter had a ‘tempered structure’ near the cutting edge having hardness HV 280. This suggests that the axe in the final stages was quenched, tempered and allowed to cool in air. It is not clear whether the axe had martensite in the cutting edges and whether the date of the axe could be 600 BC or later, since the site is dated 600 BC to AD 600.