History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c12.s1.t6: Zawar Zinc Mines
History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c12.s1.t6
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Zawar Zinc Mines
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Ancient mines at Zawar are found both opencast and underground. A rough and conservative calculation suggests that perhaps 250000 tonnes of zinc concentrates were extracted from some 2.5 million tonnes of ore in the total mined area, before modern mining commenced. Fig.7 shows a plan of the old workings at Zawarmala mine and Fig 8 presents a view of an ancient stope (Willies, 1987).
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Ancient workings are found at the outcrops on the ridge of Zawarmala, some 120 m deep below the surface. At the surface mine workings occur at intervals of 50 m or so on either side of narrow valley formed by denudation of an anticline at the top of the ridge. Most are very small openings directly into the host beds, inclined at up to 40°. Only a few shafts are visible at the surface. At one of the mines, known as Pratap khan the entry to the mine is from a small quarry, obviously the result of opencast working of ore. Excavations have been done by ‘gads’ (pointed chisels) and traces of ‘gad’ marks are common in the quarry, and in the [Figure: ZAWARMALA MINE Modern 70m level modern raise Long Stope Wide Stope Timber Chamber Main Chamber Double Arches Promonontory N Top Chamber Oldest Workings 0 metres 20]
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Fig.7. Plan of old workings at Zawar Mala mine. The most notable feature of the mine is the development of path ways and steps.
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Fig.8. A view of an ancient stope at Zawar
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Based on his observation Willies (1987) opines that it is evident that there are atleast two stages of mining: the main section with the pathway is 10-20 m wide x 2 m high which seems to cut through older much smaller ramification of tunnels, small chambers, and small climbing shafts. Most of the works seems to have been done by hammer and ‘gad’, exploiting weaknesses in the partially sheared dolomite. There is evidence of fire-setting near the entrance in the hollows in the roof, and at the bottom of workings. Waste debris is held back by carefully built stone walls, mortared with clay.
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Deep underground extensive workings exist at Zawarmala which can be followed up dip to very close to surface. The highest, perhaps, the oldest workings are formed of small arched chambers, some 3 m across and approximately 3 m high. Access is very constricted, at times one has to crawl to pass through it. It is blocked entirely at the upper end. The method of excavation seems to have combined fire-setting and hammer ‘gad’ work, with possibly the use of small picks to extract ore in narrow places. Another old and highest working is some 30 m long and 5 to 8 m high and wide. There are characteristic fire hollows in the walls, and rounded roof and pillars of firesetting. The sloping floor has been worked up dip by means of ‘benching’ using fire holes on three benches following each other. Lower still in the workings, the mine has been worked almost entirely by fire setting with very little ‘gad’ work evident. The pillars are 5 to 10 m apart and upto 5 m high, often infilled partially and sometimes wholly with dumped waste. Through the area a clear and well made path has been made, with stone and wood steps where it is steep. A sample of wood from the area has given the age 2149 years before present.
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At another place the area has double arching, one set above the other. Evidently the upper arches were formed in the original advance-dip, the lower by reworking towards the up-dip.
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Another stope 20-30 m across about 2 m high on average, with only occasional pillars is found. In this stope fireset holes are found both lateral, and in the floor and also in the roof. Timber props have been used both to hold up roof flakes and to stablise waste on the slope. Shallow trenches have been dug to convey water inflows to the path, and there are wooden launders for a similar purpose. One launder measured 5 m long u-section 30 x 30 cm. A radio carbon age of one launder gives 1920 years before present.
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At the bottom of ‘wide stope’, the ‘finger-stope’ has been developed. These are fireset inclines, about 3 m diameter, and sometimes 5 m or more of characteristic rounded section and driven down-dip at 30-40 degrees inclination. They follow richer shoots of ore. The substantial crossection presumably allowed cold air to flow at the floor and hot air to return at the roof level. No brattice was used. This decline was worked in two benches. Samples from a ‘timber chamber’ yielded an age of 2120 years.
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Another big chamber 30 m across and perhaps 20 m high was developed on the dip. It is likely that work continued using firesetting to widen the stope after the limiting depth was reached, no doubt coinciding with the removal of pillars between the two finger stopes. Burnt wood residues suggest an age of 2180 years before present.
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There are large amounts of burnt wood fragments of small sticks 50 cm or more long and 5 or 6 cm diameter, including bamboo and acacia. Fragments of reed and/or split bamboo carrying baskets were found. Several pottery lamps were found in form like small plant pots. These contain oil residues of vegetable origin and probably used cotton seeds as moderator. Their position on ledges, or near the pathway suggests that the lamps had semifixed location rather than being carried. Small jars for carrying drinking water or oil were found and some large jars probably used for carrying water out of the mine were also found.
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“One has a mental picture of some hundreds of persons at work, some carrying fuel or support timber in, and ore and rock waste out, probably using baskets carried on the head, with others conveying water in a similar way. ... specialised skilled men would include the fire-setters and timber men who constructed morticed ladders and steps etc.”
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Fire-setting was the major means of extraction. The characteristic holes created by the fires suggest that the main impact was in the floor with a reduced effect the higher above the fire the flames climbed producing the characteristic arched roof form. Thus sinking a decline was the preferential mode of attack, whilst working up - dip was done by creating and driving forwards holes in the floor. A typical depth affected by a single burn seems to have been 5 cm. Many large pieces of rock, sometimes too heavy to lift, suggest mechanical breaking methods were used, probably using iron tools and perhaps a battering ram. ‘Gad’ and wedge marks were observed mainly in narrow slits.
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Fire-setting must have created major ventilation problems. the combination of particulate material, and oxides of carbon and of sulphur, and of high humidity, must have made working conditions difficult.