Minerals and Metals in Ancient India v1.c14.s2.t6: Source of Copper at Lothal
Minerals and Metals in Ancient India v1.c14.s2.t6
- Language
- English
Source of Copper at Lothal
v1.c14.s2.t6.1
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.
v1.c14.s2.t6.2
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.
v1.c14.s2.t6.3
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.
v1.c14.s2.t6.4
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.
v1.c14.s2.t6.5
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.