History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c11.s1.t1: Metal Technology of the Harappans
History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c11.s1.t1
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Metal Technology of the Harappans
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Before we discuss copper artifacts and their technology, it will be useful to mention the types of ores and their main locations in India. The main Indian copper minerals are (a) chalcopyrite (CuS.Fe₂S₃), (b) chalcocite (Cu₂S), (c) malachite (CuCO₃). Cu(OH)₂, and (d) azurite (2 CuCO₃.Cu(OH)₂). The major copper mines are located in the 80 km long Khetri belt in Rajasthan and the Singhbhum copper belt in Bihar, which is 130km in length. Other important deposits occur in the districts of Guntur, Arcot, and Kumaon (Brown and Dey 1955; Agrawal 1971). Sources in Baluchistan, such as Shah Maksud and Kalih Zeri, have also been mentioned as probable mines for Harappan copper (Sana Ullah 1931).
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Pre-Harappan (or Early Harappan) contexts are generally poor in copper; from the pre-Harappan levels of Kalibangan, for example, we have three artifacts, including a *parasu* (hatchet). Only from Nal, in Quetta, is there a richer repertoire composed of knives, bangles, and axes.
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The Harappans were far richer in copper and also in copper tool types, although they continued to use chert blades. They had flat celts, knives, arrowheads, spearheads, chisels, razors, fishhooks, saws, drills, etc. (*Fig. 2*), in addition to vessels and metal figurines. It may be noted here that tubular drills, true saws, and needles with eyes at the pointed ends are contributions of the Harappans to the world of instruments. The Harappans were the only people in India who used metal lavishly for vessels, including a variety of vases.
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Most of them seem to have been made in two parts, the bottom and the top, and then joined together. For vessel fabrication they used sinking, raising and lapping, and for joining metal they used *running* on and riveting techniques (soldering was used only for noble metals). Metallographic examination shows that they resorted to open and closed casting, slow cooling of casting, annealing and cold work (Agrawal 1971; Agrawal et al. 1978b).
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Small animal and female figurines (for example, see *Fig.3*) were cast by the *cire perdue* (lost wax) process (*Fig. 4*), although none of the Harappan moulds is as ornate as the Chinese, nor as intricate as the Mesopotamian examples. A number of axes from Chanhudaro and Mohenjodaro show puckered surfaces, indicating that they did not always use *green poling* in open moulds; the use of green branches for poling in molten copper releases hydrocarbons which reduce the oxides, thus avoiding blowholes.
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Pure copper is not a hard metal, but it can be made harder through beating (cold work). Too much cold work, however, makes the edge brittle and it then requires heating (annealing) to make it ductile again. Alloying copper with arsenic or tin increases its hardness considerably, and today we know that copper should be alloyed with up to 4-5% arsenic and 8-12% tin for maximal ductility and hardness. We have now more than 200 analyses of Harappan artifacts (Agrawal et al., 1978b), which indicates that only 23% were alloyed with tin, 12% with arsenic, 8% with lead, besides a smaller percentage with an admixture of these elements. It should be noted that the Harappans used both Sn and As alloying and the Chalcolithic cultures exclusively tin alloying (*Fig.5*). In an effort to locate copper artifacts, we find a hatchet at Khurdi (*Fig.6*) similar to one found at Kalibangan. As regards Fig. 2 Main Harappan metal artifact repertoire
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Fig. 3 Bronze image of a dancing girl from Mohenjodaro indicates the use of cire perdue technique