Abstract
The extraction of zinc from ores began late in history, mainly because of the fact that it tended to evaporate when smelting in the open was attempted. It was only when closed stills began to be used for liquor distillation that the same method could be adopted for zinc. This technique began to be used in China and India in medieval times, the major zinc mine in India being at Jāwar in Mewar, Rajasthan. These mines remained in operation till at least well into the seventeenth century, when zinc imports from China apparently made zinc extraction at Jāwar unprofitable and the mines closed down. The famous Bidri ware datable to the eighteenth century seems to have depended for its zinc on China.
Zinc is a non-ferrous base metal, a chemical element with the symbol Zn, atomic number 30. It is a slightly brittle metal at room temperature and has a silvery blue appearance when oxidation is removed. Its mineral forms include sphalerite or zinc blend, smithsonite, calamine, zincite, wilkmite and franklinite. Its peculiarity lies in its boiling point, 906°C, which is lower than the temperature at which it could be smelt. This was surely an important reason for its falling behind copper and iron in mankind’s use of it. 1 For obtaining pure zinc, distillation technology needed to be developed, which came much later.
The history of zinc in general and its contribution to India’s material culture is quite intriguing. Zinc has been a mysterious eighth non-ferrous commercialized metal to be produced and put to various uses. 2 Zinc occurs as a metallic element in nature, but it can be obtained in pure form only by smelting ores that contain zinc. 3
The antiquity of the knowledge of zinc has led to some interesting debates. Previous research on zinc was pursued by archaeologists and philologists who have generally concentrated on the time when metallic zinc was first obtained. Extracting metallic zinc from ores posed a serious challenge to traditional metallurgy. Accidental melting of zinc ore in an open fire could never produce metallic zinc, unlike lead or tin.
As noted already, zinc has a boiling point of 906°C. Therefore, it would be in gaseous form at the temperature required to reduce its oxide to metal (950–1100°C). In an open fire or furnace, unless the vapours are trapped by means of condensation equipment, converting the vapours in the course of cooling into metallic zinc, they will combine with carbon dioxide in the furnace and form zinc oxide. Therefore, procedures for obtaining metallic zinc appeared quite late in China, as elsewhere in the world. However, the use of zinc is dated quite early in the form of a copper-zinc alloy: brass. The Chinese could produce accidental brass with zinc content of over 20 per cent as early as the Lung Shan period (first half of second millennium
Hans E. Wulff reports about the use of zinc from Achaemenian (550–330
North of Yazd, Marco Polo reports ‘tutiya’ factories at Cobinan (Kuh-i-Banan). Tutiya was obtained from finely ground calamine, which was mixed with charcoal and granulated copper, placed in crucibles and then heated. Metallic zinc thus reduced with charcoal vaporizes, but apparently it then alloys with copper in the sealed crucibles to form brass.
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The author of a Chinese text Kinvu-swi-si-ki (sixth century
In China, the period of the use of zinc has been divided into ‘approximately three stages: (a) When zinc went into copper alloys as an accompanying ore (pre-Han dynasty period: third century
In India, it has been claimed that zinc was discovered sometime in the fifth–fourth century
Irrespective of arguments in favour of the antiquity of Indian knowledge about it, zinc was in fact a late addition to the ranks of available metals when it was isolated at last. Prior to its industrial use, zinc that was used in making brass was actually contained in the form of calamine, a zinc-bearing material. The problem lay with the obtaining of pure zinc, which was an unusually difficult task, especially because, as we have seen, zinc vaporizes in the smelter instead of melting. Therefore, when heated, it would simply disappear out of the furnace. Eventually it was found that calamine should be heated in a specially designed sealed clay vessel. The continuous heating would cause the metal to vaporize, but instead of allowing it to escape to atmosphere, the vessel commonly identified as retort, channelled it into a separate chamber where it cooled. 12
An intriguing problem is associated with the appearance of retorts at certain archaeological sites that were well-known Greek outposts in India. Was there a Greek connection? In this context, we may refer to another explanation. It has been argued that the Arthashāstra II, 13–14, provides evidence about knowledge of the twin processes of cementation and cupellation for securing purity in gold and silver. Therefore, the discovery of a brass vase at Bhir Mound, Taxila (third–second century
It is instructive to note that brass as coinage metal during the second century
Prafulla Chandra Ray cites a passage from Rasarnava (twelfth century) in support of the extraction of zinc. 16 The next references he cites are to Rasaprakash asudhakara of Yashodhara (twelfth–thirteenth century); 17 Rasachintamani of Madanantadeva (tenth–twelfth century); 18 Rasakalpa (Rudrayamala tantra) (tenth–twelfth century); 19 Rasaratnasamuccaya by Vagbhata (twelfth–fourteenth century) 20 and Dhatukriya or Dhatumanjari (Rudrayamala Tantra) (of uncertain age). 21
It is to be noted that the references to extraction of zinc start multiplying from twelfth–thirteenth century onwards in Sanskrit literature; this coincides well with literary and archaeological evidence about retorts.
First of all, as J.W. Allan informs us, Indian zinc (tūtiya) was sought for in Iran, to go by a report in Abre Dulaf’s Al-Risālat al Thāniya (9th–10th century
In India, the use of retorts possibly owes its origin to its earlier application in liquor distillation reported from Taxila (150 There is much iron and steel and Ondanique, and they make steel mirrors of great size and beauty. They also prepare both Tutia (a thing very good for the eyes) and spodium; and I will tell you the process. They have a vein of a certain earth which has the required quality, and this they put into a great flaming furnace, whilst over the furnace there is an iron grating. The smoke and moisture, expelled from the earth of which I speak, adhere to the iron grating, and thus form Tutia, whilst the slag that is left after burning is the spodium.
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The first references to zinc in any Persian text comes from Nuzhatu-l Qulūb (1339–40) where the author has a chapter (interestingly the first chapter) on mines. Here he tells us that ‘some books which I have seen (say) that in Chinese towns a kind of mineral is found, that arms are made of. Striking by it is harder than by iron. It has much qala‘ī (zinc) and copper in it’. 25
The first reference in any Persian text to zinc mined in India comes, in fact, from Abū’l Faẓl Ā’īn-i Akbarī, mainly compiled in 1595. He tells us:
Zinc (jast) is deemed by some to be similar to mercury, by others to lead. Nothing about it is mentioned in scientific texts. It is mined near Jāwar (Zāwar) in the province of Ajmer.
26
Abū’l Faẓl’s insightful observation makes it quite clear that zinc was then a newly discovered or separated metal. 27 The Jāwar (Zāwar) mine in Mewar (under ṣūba Ajmer) yielded silver to the value of ₹400–500 per day, according to Munhta Nainsi, writing c. 1657. 28 Curiously, Nainsi makes no reference to zinc. He further reports that the mines provided an annual revenue of ₹250,000 in 1634–35 to Maharana Jagat Singh of Mewar, and of ₹175,000 to his successor Maharana Raj Singh in 1675. 29 Another report put the annual income of the state from the mine at ₹179,744 in 1655. 30 In 1829, James Tod in his celebrated Annals and Antiquities spoke of the ‘Jawra’ mine as mainly yielding tin and as then being long extinct. 31 It is to be supposed that his informants or he himself confused the local word for zinc with tin.
Recent excavations have established beyond any doubt that zinc was indeed produced at the Jāwar mines and in large quantities, though, again, recent estimates of the volume produced from the remains discovered may be taken with a pinch of salt. For what they are worth, two estimates have been offered of the total quantity of zinc that the Jāwar mine produced. One is for twelfth to eighteenth century: 50,000 tonnes or 83.4 tonnes a year; the other for 1400–1800: 32,000 tonnes or 80 tonnes a year. 32 Though the estimates of annual output are close to each other, their basis remains speculative.
It is possible that the Jāwar or Zāwar mines closed down in the eighteenth century, owing to competition from Chinese zinc. There is much evidence for rising imports of zinc from China. Chinese knowledge of zinc extraction has been traced to at least the period of the Ming dynasty (1368–1644), during which a text on metals gives an account of the production of ‘metallic zinc’ through the heating of calamine in a sealed clay jar. 33 By Mughal times, therefore, China was able to export zinc in increasing quantities. As early as 1600, the Jesuit fathers on a mission to Akbar’s court at Burhanpur, described ‘calaim’ as a white metal ‘which comes from China’. 34 The Portuguese, indeed, were apparently the first to bring Chinese zinc to India. 35 There was apparently a rising demand for zinc in India, which the Jāwar mines could not entirely meet. In April 1625, the Dutch noted demand at Surat for as much as 50,000 lb. of zinc. 36 The Dutch and the English Companies both began to include zinc in their shipments from China. In a missive dated 12 February 1685, the Dutch Company hoped to sell 350,000 lbs of imported zinc (‘Spiaulter’) in Bengal alone. 37 In the same year it was reported (11 December 1685) that zinc sold at ₹191/2 per man at Hugli, whereas it cost but the equivalent of ₹101/2 for the same weight in China, 38 thus yielding considerable profit to the importers.
It is possible that the large quantities of zinc imported from China ultimately made the Jāwar mines uneconomical and led to their closure sometime in the eighteenth century. The earliest account of the famous Bidri ware is possibly that of Francis Buchanan (1808–09). He described its manufacture in District Purnea, Bengal, finding it to be based on ‘tolerably pure zinc’, which he believed was imported ‘by sea’ from China. 39