Minerals and Metals in Ancient India v1.c25.s3: Argentiferous Lead Ores in Ancient India
Minerals and Metals in Ancient India v1.c25.s3
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Argentiferous Lead Ores in Ancient India
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In the earlier chapters we have reported the lead-and silver-bearing artefacts in ancient India. These metals were known even in the Pre-Harappan sites of Southern Baluchistan (*vide* chapter 2). The Harappans were acquainted with lead ores such as galena (sulphide) and cerussite (carbonate), and their smelting process which is simple on account of easy reducibility and low melting point of the metal. At Mohenjo-Daro, six per cent of the tools contained lead (assaying 1-32 per cent).
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Though Harappan gold contained some silver (electrum), the silver samples, more prolific than gold (D.P. Agrawal, 1984: 163), contained no gold but some lead and copper (*vide* Table 17.3). This means that silver was probably obtained from argentiferous galena rather than electrum. (Bhardwaj, 1979: 138) Forbes (1964: 175-232) concluded that the Pattinson Process (crystallization of lead from melt, leaving silver-rich residue)-cum-cupellation (oxidation of impurities in silver by hot air) route had been invented in the third millennium BC. This must have been followed to make Harappan silver, the starting raw material being argentiferous lead ore from Fāranjāl mine, Afghanistan or the Ajmer mine in Rajasthan.
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Table 17.3
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Per cent Composition of Some Ancient Objects Containing Silver
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| No. | Item | Ag | Pb | Cu | Au | Fe | Ni | S |
| 1. | Silver, Mohenjo-Daro | 94.52 | 0.42 | 3.68 | — | — | — | — |
| 2. | — do — | 95.52 | 1.40 | 3.08 | — | — | — | — |
| 3. | Lead, Mohenjo-Daro | trace | 99.70 | 0.15 | — | — | — | — |
| 4. | Silver, Gungeria | 96.30 | — | — | 3.70 | — | — | — |
| 5. | Punch-marked coin, Taxila | 84.14 | 0.15 | 13.01 | — | 0.15 | trace | 0.20 |
| 6. | — do — | 74.87 | 0.10 | 22.40 | — | 0.08 | trace | 0.10 |
| 7. | — do — | 72.08 | 0.23 | 25.16 | — | 0.20 | 0.15 | trace |
| 8. | — do — | 78.40 | 0.40 | 20.12 | — | 0.06 | 0.20 | trace |
v1.c25.s3.6
After the collapse of the Harappan civilization, the Post-Harappan sites continued to show lead but no silver in the artefacts. The 102 pieces of silver plates discovered with 424 copper implements at Gungeria, in district Balaghat (1100 BC-800 BC Pre-PGW level), assayed 3.7 per cent gold but did not contain any lead (Table 17.3). This suggests that silver might have been prepared from the South Indian electrum by chlorination with common salt or sulphidisation, and then cupellation of the silver chloride or sulphide.
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The punch-marked silver coins of Taxila again report lead, and also very significantly sulphur (Table 17.3), conclusively proving argentiferous galena to be the source of silver metal in the coins. Copper must have been added (13-25%) to debase the coins. The items 5 and 6 in Table 17.3 clearly show positive correlations between Ag, Pb and S and negative correlation between the three elements on the one hand and Cu on the other, indicating the extraneous nature of copper separately added to the silver matrix.