Minerals and Metals in Ancient India v1.c25.s5: The Raw Materials for the Kṣatrapa Coins
Minerals and Metals in Ancient India v1.c25.s5
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The Raw Materials for the Kṣatrapa Coins
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Agrawal et al. (1976: 135) and Shekar (1983: 178) have reported the C-14 date of 140 BC for the working of the copper-lead-zinc ore deposit at Ambamata, Banaskantha, Gujarat (vide fig. 17.3a and Table 17.1). There are extensive old workings in the areas of Ambaji (24º20 'N, 72º51 'E), Gujarat, Basantgarh and Deri (24º23 'N, 72º50 'E) in the neighbouring Sirohi district of Rajasthan. Large dumps of ancient slag, metallurgical tools, smelted metal and potteries have been found at Ambaji and behind the group of Jain temples in the adjacent Kumbaria (24º 19 'N, 72º 51 'E).
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The Ambaji deposit must have been exploited for copper, lead and possibly silver, during the pre-Christian era Śuṅga Period and the post-Christian era Kṣatrapa Period. This is strongly indicated from the analysis of the Ambāji metallic samples, Kṣatrapa era lead coins from Nagara (20º 41 '15" N, 70º 38 '33" E) and silver coins from the Buddhist site at Devnimori (23º 41 'N, 73º26 'E) (vide fig. 17.3 a and Table 17.6). The trace element analysis data (Table 17.7) clearly relate the Nagara lead coin with the Zawar ore and the Devnimori silver coin with the Ambaji ore.
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The data presented in Table 17.6 shows widely fluctuating ratios of Pb : Zn and Pb : Cu. Shekar (1983: 181) has attributed this trend to ‘deficiencies in extractive metallurgy, in obtaining pure fractions of individual metals from a multimetal ore as of Ambamata, rather than due to any deliberate attempt at debasing’. We do not agree with Shekar for the simple reason that India had already well-established traditions for selective mining and preparation of reasonably pure metals of copper, lead and silver. It is difficult to imagine the ancient smelter making silver ‘naturally’ containing 18 per cent copper (Table 17.6, sample No. 3) and smelting copper naturally containing 11-46 per cent lead (Nos. 4 and 5). Thus, the fluctuating ratios in Table 17.6 reflect, in our opinion, deliberate attempts for alloying.
v1.c25.s5.4
Forty-five lead coins were recovered from Nagara by Mehta (1968); similar coins from the identical Kṣatrapa era (2nd-4th century AD) stratigraphy had been recovered by Mehta from Vadnagar (1955) Shamalaji and Devnimori (1966). The last site yielded silver coins also.
v1.c25.s5.5
The lead coins from Nagara were circular, rectangular and square-shaped; these had variable thickness and weights ranging from 1.263 to 6.136 gm. Several of them showed the Kṣatrapa motif of bull on the obverse, mountain and moon motifs on the reverse. One coin was dated 285 in Śaka era or 363 AD. The comparative study of impurity patterns (some 25 elements) enabled Hegde (1968: 519) to correlate the Nagara lead coin with the Zawar galena ore except in terms of calcium which was found by him to be strangely absent (?) in the Zawar galena concentrate.
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Table 17.6
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Some Multi-metallic Samples of the Kṣatrapa Period (2nd to 4th century AD)
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| | | Elemental Percentages | | | | | Ratios | |
| | *Pb* | *Ag* | *Zn* | *Mg* | *Al* | *Cu* | *Pb/Zn* | *Pb/Cu* |
| 1. Nagara Lead Coin I | 97.40 | + | 1.26 | 0.26 | 0.38 | + | ~80 | large |
| 2. — do — II | 97.21 | + | 1.18 | 0.42 | 0.29 | + | ~85 | large |
| 3. Devnimori Silver Coins | 0.86 -1.21 | Bal- ance | 0.17 - 0.21 | N.D. | N.D. | 18.00 Balance | ~5 | ~ 0.05 |
| 4. Ambaji Copper Sample | 11.00 | N.D. | 0.85 | N.D. | N.D. | 13 | 0.13 |
| 5. Ambaji Smelted Sample | 45.97 | N.D. | 0.15 | N.D. | N.D. | 47.72 | 300 | 1.00 |
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+ means present. N.D. not determined. Balance: the rest out of a total 100.
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Table 17.7
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Trace Element Impurity Patterns and Kṣatrapa Coin-Ore Correlation
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| | Pb | Ag | Zn | Cd | Au | Cu | Ca | Cr | Co | Ni | Hg | Bi | Sn | Be | Ru | Pt | Mo | Ir | U |
| 1. Nagara Lead Coin | H | + | + | + | + | + | + | - | - | - | - | - | + | + | + | + | - | - | - |
| 2. Zawar Galena | H | 40 | + | 200 | + | + | - | - | - | - | - | - | + | + | + | - | - | - | + |
| 3. Devnimori Silver Coin | + | H | + | + | - | + | ND | + | + | + | - | + | - | - | - | - | + | + | + |
| 4. Ambaji Ore | H | 20 | H | 400 | - | H | ND | 2 | 15 | 15 | - | 5 | 5 | ND | ND | ND | 5 | ND | ND |
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Legend: H means High; + present; - Absent; ND Not Determined Figures in ppm. Fe, Al, Mn, As, Sb, V present in all samples.
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The above correlation is indeed good (*vide* Table 17.7). But then Hegde ran into difficulty when he tried to correlate the Devnimori silver coin with the Zawar galena ore. Since the correlation was negative, he hastily concluded (Hegde, 1967 and 1968: 518) that ‘the silver metal was not extracted from the indigenous source but was probably imported’. Later, Shekar (1983: 179-80) showed that the trace element pattern of the Devnimori silver coin clearly matches with that of the Ambāmātā deposit only a hundred kilometre away (*vide* fig. 17.3a and Table 17.7). Specifically, the elements found missing in the Zawar galena sample viz., Cr, Co, Ni, Bi and Mo were detected in the Devnimori coin and the Ambaji ore; gold present in the Zawar sample was not present either in the Devnimori or Ambaji samples. This is a classic example of the hazard in ore-artefact correlation; possibly the silver metal was not ‘imported’! Shekar explained the absence of tin in the silver coin (tin is present in the Ambaji ore) by suggesting that the volatile metal might have escaped during smelting.
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We have mentioned earlier that the C-14 dates (*vide* Table 17.1) indicate that not only copper but also zinc, lead (and possibly silver) were extracted during the medieval periods of AD 1070-1440 from the Ambāmātā deposit in Gujarat and Bandlomattu-Agnigundala area in the Andhra Pradesh. At Agnigundala, mining was done in the nature of long, open trenches as well as along the dip of the lodes reaching a depth of 30 m. (Ziauddin, 1961) The ancient Gavulabhavi lead deposit in the Cuddapah district, Andhra Pradesh, was developed similarly through 280 m long surface diggings and underground shafts reaching 50 m below the surface. (Rao and Rao, 1977)
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At Agnigundala, extensive mining, mineral processing (crushing, grinding and benefication) and smelting (of copper and lead) took place, which is evident from the rock dumps, slag heaps and appliances such as cupolas, crucibles and tube-like bodies, tapering somewhat and closed at one end. A few pieces of lead were found in the heaps assaying 99.5 per cent lead and 220 ppm silver. (Ziauddin, 1961: 120)
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It may be noted that many Harappan and Post-Harappan artefacts contained arsenic, antimony, nickel, etc. the sources of which are not known. Specimens of löllingite (iron arsenide) were found; these were evidently used for arsenic alloying of the Harappan copper artefacts. Antimony- and nickel-bearing copper ores or ingot might have been brought from cutside the sub-continent, although the possibility of indigenous resources cannot be altogether ruled out.