Minerals and Metals in Ancient India v1.c26.s4: Making of Zinc and Brass in Ancient India
Minerals and Metals in Ancient India v1.c26.s4
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Making of Zinc and Brass in Ancient India
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As regards the recovery of zinc from the ore, the crucible reduction/distillation method was put to large scale commercial practice in the thirteenth century AD, and this will be described later. Indirect and circumstantial evidences suggest that the distillation method was in vogue much earlier, probably from the fourth century BC onwards, although not in a large scale as we find in the thirteenth century AD context.
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In this connection we recall the evidence from Rampura-Agucha presented in the previous chapter. The zinc-lead-silver ore in the site was selectively mined at least as early as 370 and 250 BC (vide Table 17.1). An appreciable amount of zinc must have been separated from the zinc-rich ore (present-day ore in the site contains 13.5 % zinc) as revealed from the low-zinc content slag. One sample of slag (No. 4 in Table 17. 4) assayed as low as 0.01 per cent zinc. (Tiwari et al., 1984: 85) Near the slag dump area several retort-like pieces were reported. When assembled, their appearance suggested a cylinder approximately 20 cm long with walls about 4-5 cm thick and an innermost pipe-like feature with a coating of dirty white material, mainly zinc sulphate. They could not be mistaken for tuyeres but for their closed pointed ends. This is highly suggestive of a used retort. Along with this, some thin-walled tube-like material containing a thin coating of blister type material was also found. (Paliwal *et al.*)
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It is conceivable that the retorts were being used in the said context for roasting zinc ore to obtain the light, white, smoky zinc oxide, which the ancient Greeks called pompholyx, philosopher’s wool. In the modern zinc plant at Udaipur, roasting of zinc sulphide concentrate produces not only zinc oxide (and sulphur dioxide gas) but also some zinc sulphate which was noticed in the fourth-third century BC retort in Rampura-Agucha*. The said retorts, already found sealed at one end, must have been closed or sealed at the other and also to prevent the escape of smoky zinc oxide into the atmosphere. The retorts were possibly modified to serve as reduction distillation chambers (to produce metallic zinc), the final version of which, noticed in the thirteenth century AD context, would be described later. Very significantly, Tiwari *et al.* (1984: 85) noted that the slag sample (no. 4 in Table 17. 4) containing only 0.01 per cent zinc but as high as 9.30 per cent lead, was “attached to baked earthen materials which could be the part of the earthen appliance used for smelting”. We suggest the possibility that the earthen appliance was a zinc distillation retort.
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We may now turn our attention to the antiquity of brass in ancient India. Before the discovery of zinc metal in India (made by the distillation route) some time during the fifth-fourth century BC, brass could be made only by the cementation route in which one of the following—zinc ore, sphalerite concentrate or the roasted product philosopher’s wool or zinc oxide—was smelted along with copper ore. The traditions of making philosopher’s wool and cementation brass** could have persisted even after the discovery of the distillation process of making zinc. As we have indicated earlier, the distillation route of making zinc and alloying this with molten copper was the only way of making high-zinc (more than 28 %) brass such as the fourth century BC Taxila vase (34.34 % zinc).
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We have noted the compositions of the Taxila brass samples in Table 14.7 and discussed the zinc-containing artefacts of Taxila in the same chapter. Some of the other early brass samples from ancient India have been reviewed by Neogi (1917, 1979: 40-42) and Ray (1956: 94-95), an extract of which is presented below.
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∗ There are also remains of zinc furnaces at Sojat in Jodhpur.
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∗∗ The second century AD text *Rasaratnākara* of Nāgārjuna mentions (1.3) “What wonder is it that calamine (zinc ore) roasted thrice with copper converts the latter into gold”. This is an allusion to the making of yellow gold-like cementation brass. The same text (1.31-32) also refers to the reduction-distillation of calamine yielding zinc : “an essence of the appearance of tin”.
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Brass articles of the first century BC or AD have been found on excavation of ancient stūpas. General Ventura executed operations for the examination of the stūpas at Manikyalaya in 1830. Three deposits were obtained of which the third, at a depth of 64 ft, consisted of a copper box enclosing a brass cylindrical box cast and beautifully turned on the lathe. The lid of the brass casket was found on cleansing to be inscribed. From the inscriptions on the various articles of this deposit and the accompanying Indo-Scythian coins, the great tope at Manikyalaya has been identified to be a mausoleum of the Indo-Scythian king Kaniṣka (1st century BC or AD) (Wilson, Asiatic Researches, Vol. 17, p. 601; Cunningham, Journal of Asiatic Society of Bengal, 1854).
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Another inscribed brass urn of the same date as the former has been discovered in a tope about 30 miles west of Kabul in the district of Wardak. This urn which in shape and size approaches closely the ordinary water-vessels in use in India to this day, was originally thickly gilt and its surface has in consequence remained well-preserved. (Princep’s Indian Antiquities edited by Thomas, Vol. 1, p. 162 quoted by Neogi, 1917, 1979: 40) As regards coins, both brass and bronze were used in ancient India for coinage. Circular punch-marked brass coins of Dhanadeva and Āryavarmā of Ayodhyā (circa 1st century BC) have been found. Brass coins of kings of several other dynasties living at that time have also been collected (vide Vincent Smith’s Catalogue of Coins in Indian Museum). From these arachaeological and numismatic evidence it is clear that brass was in common use in ancient India during the first century BC. A small number of die-struck coins of the Pre-Gupta and Gupta period, including a piece attributed to Candragupta II, are considered to be made of brass.
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Gradually brass was used in making statues of gods and goddesses mainly because it was yellow and looked like gold. An inscribed brass statue of Buddha, 30 cm high and 13.5 cm wide, of the sixth century has been discovered in a dharmaśālā at Fatehpur, a village 20 miles due west of Kangra-Kot (Annual Report, Archaeological Survey of India, 1940-45, p. 107). Another inscribed brass statue of a large size of about eleventh century discovered in Bengal has been preserved in the Dacca museum. We would present some technical details about brass statues in chapter 20.
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The most remarkable and gigantic work of brass has been described by the Chinese traveller Hiuen-Tsang who saw near the famous Nalanda convent “a vihāra of brass built by Śīlādityarāja (Harṣavardhana ruling 606-47 AD); although it is not yet finished yet its intended measurement when finished will be 100 feet”. When completed, this would undoubtedly have been a magnificent example of the skill of the ancient Indians in brass-work.
Cites (1)
- Rasaratnākara — Sāḷva, Kannada