History in Mines

[Photo: Twitter]

On a map of India, the dots have been simply marked as Z D A. Those three letters stand for Zawar, Dariba and Agucha and the map figures in a report titled ‘Early Indian Metallurgy’ ~ The production of lead, silver and zinc through three millennia in north-west India’. Dr PT Craddock, with KTM Hedge, LK Gurjar and L Willies finalised the report, first published in 2017. It describes the survey, excavation, and scientific study of three major mines and metal production sites in the Aravalli Hills of Rajasthan, formerly the Mewar region of Rajputana.

All three sites have very extensive remains of mining and smelting activity that occurred through three millennia, that is 3000 years of history that lies in mines. The major minerals exploited at these mines were mixed lead/zinc sulphides. Zinc is currently the principal metal extracted together with minor amounts of lead and zinc.

Till date, the three mines ~ Zawar, Dariba and Agucha ~ are categorised as ‘heritage mines’ by Hindustan Zinc Ltd, now part of the Vedanta Group, and continue to be mined. Dr Paul T Craddock, the Emeritus Researcher, Conservation and Scientific Research at The British Museum, London explained in a media interview in 2019, “In antiquity the driving force behind the establishment by the Mauryans of the major mines at Agucha and Dariba, was the production of silver but at Zawar it is more likely to have been zinc oxide. In the medieval and postmedieval periods some lead and copper were produced at Dariba, mining had ceased altogether at Agucha.

But at Zawar zinc metal was produced by advanced processes at high temperature distillation, almost certainly the first production of zinc on an industrial scale anywhere in the world.” It certainly marks a first for the sub-continent and challenges the Eurocentric view of technological superiority with new scientific facts. The birth of the project to study mines of Mewar is fascinating. The report states, “In 1980 Mr Kenneth Bush of Zinc International, RP Kapur of HZL and PT Craddock of British Museum met in London to discuss the feasibility of the project to research into the history of zinc production at Zawar.

The British Museum Research Laboratory (later the Department of Conservation and Science) was already engaged in research into development of copper alloys, especially brass. The Department of Archaeology at the MS University Baroda had a longterm interest in all aspects of scientific archaeology and KTM Hegde had already carried out surveys of early mining activity in the Aravallis. None of the organisations had the expertise in underground explorations and recording of early mine workings.” Said Dr Craddock, “That is why the team of mining archaeologists at the Peak District Mining Museum was invited to join.

They had worked on ancient copper mines in Israel and copper, silver mines in Spain. L Willies brought his European experience to the Aravallis. In 1982 the joint project was set up and it was the potential of Zawar which aroused our interest.” The project was completed in seven years, in 1989, with four short seasons in the field and much longer sessions in laboratories and libraries both in UK and India.

The production of zinc by distillation is described in several iatrochemical texts from the first millennium CE, and the translation of these laboratory methods into a viable commercial chemical process in the medieval period was a remarkable achievement. Iatrochemical refers to use of chemicals for medicinal purposes; zinc quite clearly had pharmaceutical uses, known to Greeks, Romans and the different socio-religious groups across the sub-continent who were developing their own medical systems. What the report highlighted was that these Aravalli mines, in the region of Mewar, were major and complex industrial enterprises taking place well outside the Eurocentric Middle Eastern areas that were the source of most studies of early technology.

The scale and technical sophistication of the processes represented were quite unexpected. In the post-medieval period, these mines had been abandoned or were in serious decline; this was the dawn of the colonial age which witnessed economic and commercial subjugation, leading to decline and ultimate extinction of indigenous technologies. In the 18th and 19th centuries CE, this was a common occurrence through the world. Archaeo-metallurgy and archaeology pose innumerable challenges for its practitioners. Dr Craddock, in the report, explained that simple tasks like ore sampling can throw up questions. “As exemplified by Zawar in antiquity, the potential ores of zinc, silver and leader were all mined.

But which were the ores actually sought at particular phases in the mine’s history is still not known for certain,” he said. He added that the ores found in the mines today are the ones which the previous miners did not want! He gave the example of Agucha where the argentiferous minerals were removed but the zinc rich deposits were left. “In Zawar, for example, the silver content of the minerals left in the huge ancient galleries is low, but it might have been much higher in the ore that was removed, which once occupied space now several metres from the present walls,” the report revealed.

Dr Craddock explained the significance of ascertaining the smelting process in these ancient mines. What the visitors today can see are featureless heaps of production debris spread over kilometres, often quite deep too, as in Dariba. “At Zawar, the zinc smelting furnaces have survived in situ, in their original place. This is a rare occurrence and a boon for the archaeologists,” he said. In the past, archaeologists charged with investigation of sites of early metal production tended to avoid slag heaps ~ which was unfortunate as this is where the process information can be found.

They were concentrating on ancillary buildings, fortifications, road systems and burials. Information on the smelting process lies in the debris itself. The slags and associated refractory fragments contain a direct and permanent record of the smelting process from the study of which principal operating parameters can be established. “It is difficult to date slag heaps; we relied primarily on radiocarbon dating, fortunately there were usually abundant quantities of charcoal found.

Slag itself is the principal component of most heaps and a selection of three typical pieces from every layer, about 8 sq cm, should suffice for scientific study. Refractory fragments are also collected, quantified, and selected for study,” Dr Craddock said. At Zawar the aim was to sample the selection of retort and slag heaps, the almost intact furnaces that were still bearing their last load of retorts; this led to their excavation in a more conventional archaeological fashion. “We could establish heat regimes of refractory pieces obtained from precise locations in and around the furnace structures,” he said, in effect meaning that they could ‘see’ the Zawar smelting process in action even though they were separated in time by centuries.

A range of analytical methods was used including optical microscopy, thin section petrography, scanning electron microscopy with energy dispersive Xray analysis, X-ray diffraction and atomic absorption spectroscopy at the laboratories of HZL and British Museum, as well as inductively coupled plasma atomic emission spectroscopy. Although large-scale industrial enterprises were in progress at these mines contemporary with major mines of the classical world, they have previously received scant recognition, even in antiquity when they were in operation. Said Dr Craddock, “We wanted to expand the study of industrial technical innovation and establishment of large-scale production beyond the usual Eurocentric view ~ the development of zinc distillation process at Zawar is important.”

Way back in the first millennium CE, methods of producing, condensing metallic zinc were established at Zawar. The zinc oxide was probably intended for brass production too. What is significant is that systems had been developed to collect zinc vapour as a metal on an industrial scale, based on the pre-existing laboratory methods. The real innovation was to develop these into viable industrial processes. The mines at Zawar would always have been under the control of the ruling authority of Maharanas of Mewar, whose capitalcity was Chittaurgarh. Clearly, the Kingdom of Mewar encouraged and supported real innovation and industrial scale production. At Zawar there must have been hundreds, if not thousands of furnace blocks, fitted with components such as perforated plates with identical dimensions. Clearly tens of thousands of these components must have been made in central workshops to maximise efficiency and to ensure maintenance of overall control. Dr Craddock and the team went on record to state that “we were impressed by the scale and obvious systematic organisation of the early operation, so much at variance with the European descriptions of the last indigenous mining operations still taking place in 19th century India.

This surprise was even greater because it had been assumed from the excellent state of preservation that these must be late workings contemporary with the last recorded operations in the 18th and early 19th century at Zawar.” Radiocarbon dates showed underground mine workings to be ancient; that is to say, the previous millennia operations had been conducted in a more superior fashion than those employed in the 19th century CE. It is a real tribute to our ancestors, a historical nugget dug out deep from the mines of Mewar.

(The writer is a researcherwriter on history and heritage issues, and former deputy curator of Pradhanmantri Sangrahalaya)