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Minerals and Metals in Ancient India v1.c14.s2: Different Metals

Minerals and Metals in Ancient India v1.c14.s2

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Contents

Different Metals

Copper and Bronze

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The copper and bronze objects from Lothal can be divided broadly into five categories, i.e., tools, weapons, personal ornaments, objects of domestic use and figurines. The line of distinction between tools and weapons was very thin because certain tools such as axes could be used as weapons for offensive or defensive purpose. The personal ornaments formed the bulk of the copper objects which were nearly 1500 in number; it has not been possible to determine the shape and the use of more than one thousand objects because of corrosion. (Rao, 520)

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Most of the copper and bronze objects were obviously made by casting, but a few shaped and finished by hammering. Axes and chisels were heated and hammered after casting until they reached the atmospheric temperature. Thus it is evident that forging was well-known to the Lothal smiths. Chanelled crucibles with thick walls of clay mixed with sand were used for casting long bars which were subsequently hammered into chisels, rods etc. The thicker bars appear to have been cut into thinner ones as indicated by the grooves on some of them. The reason for not casting socketted daggers, arrowheads and shaft-hole axes is often attributed to the nonuse of closed moulds of more than one piece. But it may be noted here that the use of close moulds of more than one piece was made in casting figures in cire perdue technique.

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As an industrial and trading community, the Harappans devoted more attention to the improvement of the tools needed by the carpenters. This can be inferred from production of the advanced tools such as the curved saw with teeth, the auger-bit with twisted grooves, the plainer-bit with concave margins, the needles with eyelet at the piercing or flat-end. The personal ornaments consisting of the corrugated bangle, the amulet with a crouchant bull-figure, the bird-headed pin and the pendants and rings received the special attention of the coppersmiths of Lothal. But this does not mean that they were totally ignorant of the advanced tool-types. The spearhead with a folded socket and rivet-hold found at Lothal, indicates professional sophistication. Anyhow, the technicians concentrated on the production of ornaments, figurines and tools for the craftsmen. This fact is also borne by the use of bronze for making mirrors, bangles and rings, rather than axes, chisels, daggers and spearheads. Here the production of an alloy of more pleasing colour and lustre appears to have been one of the chief considerations in using tin with copper in making ornaments. (Rao, 520-22)

Bronze

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Not only copper, low-tin bronze was also used for making pins, mirrors, rods, chisels, flat axes, daggers and arrowheads; high-tin bronze was used for bangles and pins. The hardening property of lead was also known to the Lothal folk. They made use of this knowledge in hardening tools having sharp edges. Tin became a rare commodity in Sumer by 2700 BC until it could be had once again by 1500 BC. Sayce says that tablets from Kara Huyuk refer to tin which was a rare and precious metal in Babylon in c. 2500-2200 BC. It is perhaps during this period that bronze was being introduced in the Indus Valley and Kathiawar by the Harappan traders. Hence it had to be very sparingly used. Out of 71 copper objects from Lothal examined in four lots by Lal, the tin contents in two bangles were 11.20 per cent to 11.82 per cent. One grooved rod contained 9.02 per cent, a mirror 5.47 per cent, a pin 13.80 per cent, two chisels 9.02 to 9.62 per cent, an engraver 3.96 per cent, a spear 2.27 per cent. Thus only eight out of 71 objects may be said to have contained some appreciable quantity of tin. (Rao, 523)

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Another important point which emerges from the analytical data is that although bronze, both low tin and high tin, was in use at Lothal, it is difficult to say whether the use of tin was intended to produce a metal harder than copper, which was to be used for the production of tools with keen cutting edges, or tin was used just to produce an alloy of a more pleasing colour and lustre. The examination of the two chisels show that whereas one contains a high proportion of tin viz. 9.62 per cent, the other is completely free from it. If the use of bronze for producing tools with a keen cutting edge was well understood, it is difficult to explain the presence of tin in one chisel and its total absence in the other. The same statement is true of the two bangles, one of which is made of copper and the other of tin (11.20 per cent) bronze. It seems that although the use of bronze was understood, it was not used in a systematic manner for the production of special types of artefacts requiring suitable hardness, durability and a sharp cutting edge; however, there is no doubt that both copper and bronze were in use. (Rao, 652)

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From the above analytical work, it is concluded that artisans of Lothal were well conversant with the use of copper and bronze. It seems that for the objects of decorative and ornamental value, the use of bronze was considered essential. Its use was also considered essential for the strength and durability of the tools, and cutting edge in axes and chisels etc. (Rao, 652)

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Most of the copper and bronze objects examined were evidently made of casting; shaping and finishing by hammering would also appear to have been practised. The mirror which is made of a low-tin bronze was probably heated and hammered after casting until it reached the atmospheric temperature; the same can be said of the celts, axes and chisels. The technique of forging was thus practised by the metal workers of Lothal.

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The presence of such a high proportion of tin cannot be treated as accidental; it was used for producing a metal harder than copper; bronze-making and working reached a fairly high degree of technical excellence in those remote times. (Rao, 653)

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It has been proved that the inhabitants of Lothal were acquainted with lead. A sleeved axe used for fashioning copper objects contained 2.51 per cent lead. An unidentified object contained 1.64 per cent lead. (Rao, 523)

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Two specimens have been found to be made of lead; both of them are free from copper, iron, tin, zinc and silver. Nickel has been detected in traces in one lead specimen, whereas the other specimen shows 99.54 per cent of lead. It seems that lead of a high degree of purity was manufactured by the metal-workers of Lothal. (Rao, 655)

Manufacturing Objects

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The main objects were axes, sometimes with long narrow blade or broad blade; spearhead, arrowhead, razor, chisels, dagger head, mirror awls and needles, nails and rods, fish-hooks and saw. Among the personal ornaments that were made of copper and bronze were bangle, ring, ear-ornament, beads. There were few animal figures also, such as bull, hare, dog, bird, fowl etc. Other things fabricated were chair, spoon, jar, mirror etc. (Rao, 529-36)

Copper Ingot

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Copper ingots were found at Lothal. The bun-shaped ingot contains 99.81 per cent copper and no tin or any other alloy. The ingot of Mohenjo-Daro and that of Lothal closely resembled. These were plano-convex in shape. All these were found in a house which is considered to be the quarter or workshop of a metal-worker. The concave under-surface of the ingots suggests that the pit in which they were run had a convex floor. The ingots from Susa also have a concave under-surface and short projections. Some scholars think that Lothal and Mohenjo-Daro imported copper ingots. This crude metal was normally remelted for refining in clay crucibles, which were then broken up for the recovery of the purified metal. (Rao, 520-21)

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The analysis of the ingot shows that it is made of copper of a high degree of purity, i.e., 99.81 per cent and is free from tin, lead, zinc and arsenic but contains only traces of iron and nickel as impurities. (Rao, 653)

Manufacture of Copper

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The evidence of copper-smith’s workshop has been revealed from the Phase IV. There the mud brick structure consists of two rooms measuring 10 x 12 ft and 12 x 8 ft, internally, the overall measurement being 17 x 24 ft. A furnace rectangular on plan, measuring 2 ft 6 in x 2 ft is skirted by burnt bricks placed vertically on end. Other finds from the workshop include a copper chisel and two terracotta crucibles. A unique feature of the construction of the shop is that the cross-walls, providing entrance to the furnace-room, are not built in one straight line. Another feature of the workshop is the provision of a niche in the outer face of the western wall on the road side. (Rao, 95) Two types of furnaces used by copper-smiths are laid bare in Block A. One of them assignable to Phase III is more or less a circle on plan with a rectangular projection for supply of fuel. A thick bowl of coarse grey fabric with traces of copper and fragments of a copper chisel and a rod were found here. The second furnace laid bare in house No. 154, a muffle and a copper pin found near the structure go to prove that the structure was used as furnace by a copper-smith. In both the cases the crucibles were placed on burning coal in the enclosures as is done even today. (Rao, 83)

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One circular kiln of mud-bricks, 6 ft in diameter and 2 ft 3 inch deep, uncovered at Lothal near the copper-smith’s workshop appears to have been used for remelting ingots as suggested by an earthen bowl found here. Large sheets of metallic copper, reduced to copper carbonate due to prolonged mineralisation on account of the saline soil, have been recovered in the form of flattish chunks from the vicinity of the smithy. The smithy was situated near the nullah on the northern fringe of the town. The anchor stone found on the brick-embankment of the nullah indicates that boats were anchored here possibly for unloading the heavy metals.

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In spite of the destruction of the town in Phases III and IV, the copper-smiths re-established their workshop near the nullah in Phase V. Five small rectangular sink-like brick pavements skirted by bricks on edge and inter-connected with tunnels are laid bare in the workshop wherein several copper-smiths must have been working under a single roof. Near each sink, a pot-furnace containing ash and bits of muffles were noticed. Among the important finds mention may be made of two terracotta crucibles, small lumps of copper and a crescentic sleeved axe used for shaping copper and bronze objects.

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From one of the rooms of lower town a rectangular furnace of burnt bricks had been laid bare. The contents of the kiln were ash and fragments of terracotta crucibles. A stone mould used for casting pins and awls, a copper pin, a broken copper chisel and a hammer stone with a socket for hafting are among the other finds from the workshop and its vicinity. At both the sites the kilns do not have any vent. They appear to have been used for melting the ingots in open bowls.

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Two other types of kilns have been noticed at Lothal. One of them built near the workshop of lapidaries in Block F is circular on plan. The occurrence of several baked beads and pebbles of agate and carnelian in and near the kiln indicates that the structure was used by the lapidaries for baking raw materials as well as the finished product. But the possibility of the kiln having been used by copper-smiths for remelting copper need not be ruled out. (Rao, 522-23)

Source of Copper at Lothal

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S.R. Rao has observed that Mohenjo-Daro copper contained substantial amount of arsenic, and Lothal copper did not show any trace of arsenic. From this observation he suggested that Rajasthan copper ore which contains arsenic was the source for Mohenjo-Daro objects only, and Lothal copper came from Oman. There may be alternative explanations for the observed facts.

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It is proven that there was deliberate arsenic-alloying for Mohenjo-Daro copper. Not all copper ore from Rajasthan is arsenic-rich. Rao has himself recorded that Madhan-Kudhan section copper ore contains arsenic in trace amgunt, the per cent figure being in the fourth place of decimal.

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Analysis of thousands of copper artefacts shows a wide spectrum of impurity levels which could not be due to deliberate alloying. Thus diverse kinds of ores (some from Rajasthan) might have been used. The impurity level variation noted were: 0-4.02 per cent Fe, 0-13.8 per cent Sn (deliberate alloying), 0-3.6 per cent Pb, 0-2.48 per cent Ni etc.

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One highly oxidised antiquity (no. 4189) was a copper object and analysed 70.7 per cent Cu, 0.9 per cent Fe and 6.04 per cent Zn, 6.04 per cent acid-soluble component (probably carbonate) and rest oxygen. The high zinc content suggests that the ore might have come from South Rajasthan (Ahar-Zawar area). Rao has reported another sample of cementation brass from 1500 BC submerged Dwārākā.

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The high purity ingots of copper (99.81 per cent) and lead (99.54 per cent) suggest that the Lothal technicians had learnt the art of purification of impure metals, and de-arsenification in the first case.

Gold

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Apart from a large number of micro-beads of gold used in the necklaces, Lothal has yielded 110 gold objects of various sizes. The variety of objects used and the artistic skill of the jewellers are evident from the personal ornaments found at Lothal. (Rao, 632)

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Thin foils and beads of gold found at Lothal suggest that sheet-metal was beaten into foils. Casting was also widely practised. The goldsmiths must have possessed adequate skill and knowledge of metallurgy. Joining was done either by sweating or soldering. In the case of beads the midrib concealed the joints. Controlled heating was also applied for joining. The use of copper as an alloy for soldering between the spirals of coiled gold rings clearly suggest the use of an alloy. Conical objects and rings of gold were joined by sweating.

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Thus the high degree of precision, uniformity and control noticed in fashioning gold jewellery reveal a mastery over the technique comparable only with that of Sumer. The minute barrel-shaped and circular beads reveal the unerring control, the jewellers had in fashioning minute objects. An example of expertise in applied decoration is seen in jasper beads bordered with a gold cap at both the ends. The great economy excercised in using the precious metal is attested by the process of laying thin foils of gold over lac, as is even now the practice in India. Hollow-cones or conical caps of varying sizes in gold were found at Lothal. Another important find from Lothal is a gold-ring with a corrugated surface produced from a gold-sheet. (Rao, 633-34)

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The analysis of the gold from Lothal has revealed that a natural alloy, electrum, with a high percentage of silver and free from lead, was used by the goldsmiths in making pendants and other ornaments. After the analysis it has been proved that alluvial gold was not used by the Lothal folk.

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About the source of gold it is believed that the Neolithic folk of South India had worked on the gold-bearing deposits and their contact with the Harappans might have resulted in the trade in gold, steatite and other products of the mineral-rich areas. An important evidence in favour of the theory of the Neolithic folk working near the gold mines in Kolar area is the occurrence of the burnished grey ware and the black- and red-ware in North Arcot district of Tamil Nadu situated 40 miles away from Kolar Gold-mining area and about 50 miles from the ancient workings near Hosur in Tamil Nadu. Tekkalakotta and Piklihal have also yielded burnished grey ware along with gold objects. Mention has already been made of other evidences of contact such as steatite disc beads and carnelian beads characteristic of Harappan settlements occurring in the Neolithic sites. (Rao, 632-33)

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The earliest datable evidence from the Hutti mines is Carbon-14 date for the wood specimen, bp. 1890 ± 70 years. Allchin confirmed that the shaft was worked as deep as 250 ft in the opening years of the Christian era. There were evidences of fire-setting, crushing and rubbing of the rock prior to extraction of gold.

Silver

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Although no silver specimen has been found from Lothal, a good percentage of its use has been revealed from the gold objects and some with copper.

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The specimen of gold from Lothal has invariably shown the presence of silver and more or less complete absence of copper. There is no doubt that an alloy of gold and silver, not containing copper, was used by the goldsmiths of Lothal. There were similar findings from Harappa and Mohenjo-Daro. One pendant from Lothal has given the following result: 66.55 per cent gold and the rest silver. The other pendant which is light yellow has given the following composition: 58.52 per cent gold and the rest silver. From the above data it is clear an alloy of gold and silver containing about 30 per cent and 40 per cent of the silver was used for making pendants. Since the proportion of silver in the pendants compares favourably with that in the native alloy electrum, it would be natural to attribute the source of the material of the pendants to this natural alloy. This view is further supported by the fact that the pendants are completely free from lead as well as copper. Therefore, it seems probale that the alloy was not prepared artificially by mixing metallic gold with metallic silver, but most probably native alloy, electrum was used for making the pendants. As gold has been found associated with silver in these objects, so it would therefore not be unreasonable to assume that alluvial gold was not used by the goldsmiths of Lothal. (Rao, 664-65)

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In two specimens of Lothal, silver was found considerably contaminated with copper: 54.65 per cent of silver and 2.67 per cent of copper and 86.57 per cent of silver and 7.87 per cent of copper respectively, the former specimen containing 3.29 per cent of iron in addition. Apart from contamination with iron and admixture with copper, these two silver objects have been found to be free from lead and only one of them contains traces of nickel. (Rao, 655)

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One specimen made of silver (scraper) has been found to contain 71.2 per cent of silver. This object was found to consist of sound metallic core made of silver and the outer layer represented oxidised copper as cuprite. (Rao, 657)

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