History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c12.s1.t3: Khetri Copper Area
History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c12.s1.t3
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Khetri Copper Area
v1.c12.s1.t3.1
Lay Jains are believed to be responsible for mining copper in Rajasthan many centuries ago. Evidence of same type of work as in Rakha mines are found in a number of workings now known as Khetri copper mines in Rajasthan which occur in a long range of quartzite hills in Rajasthan. Along a length of 15 miles (24 km) numerous openings are met on the crest of these hills connected to underground excavations which in some cases open out into considerable underground excavations worked out areas. These in some cases are a few hundred feet long and up to 40 ft (12.19 m) wide. Tunnels fan out from these open excavations following rich lodes of ore and workings have reached to a depth of 500 ft (152.40 m) below the hill top. The underground galleries or tunnels are 5 ft × 4ft (1.5 m × 1.2m) or 4ft × 3ft (1.2 m × 0.91 m) and have their sides notched or cut so as to allow ingress and engress without the use of ladders. In order to get fresh air the ancients drove galleries to puncture the hill sides at several places and dilute the vitiated atmosphere. The age of these mines is reckoned to be Chalcolithic Age, (Bose, 1968).
v1.c12.s1.t3.2
The ore was dislodged at the face by fire-setting and quenching it with water and thereafter it was extracted with chisel and hammer manually. The broken ore was transported out of the mine in baskets carried over the heads of a series of labourers.
v1.c12.s1.t3.3
Brooke and Boileau have given excellent accounts of mining and smelting of copper in the Khetri area in their papers which give an insight into the mining techniques employed in the ancient days and are summarised below:
v1.c12.s1.t3.4
As said earlier the ore was cracked at the face by fire- setting. For fire-setting at the face some 150-200 maunds (5.6- 7.5 tonnes) of fire wood was stacked in a compact manner which was set on fire, and immediately thereafter miners went out of the mine quickly lest they should be smothered in the galleries and meet with fatal accidents. On approximately the third day of fire-setting the miners went inside the mine to find that the rock/orebody at the face was cracked and split into huge masses by the violence of intense heat and when the workings were sufficiently cooled, they proceeded with the work of extracting the ore. Each face worker was provided with a lamp, a ‘gad’ or mining chisel and a small basket. The lamp placed upon workmen’s head not only provided illumination for the execution of his work but also enabled him by watching the glittering particles of metal to detach only such portions of the ore as might promise him the best remuneration for his labour. While at work the miner seated himself upon his heels with the lamp upon his head, the hammer in his right hand and the ‘gad’ in his left hand and the small basket upon his knee in which he received all the fragments of ore that were struck off by the chisel.
v1.c12.s1.t3.5
The bamboo baskets of ore were passed along a chain of persons, usually 4 to 12 in number who set upon their haunches in the galleries or stood on the niches cut in the shafts, when the whole reached the foremost man, they moved upwards and again ranged themselves and this was continued until the mouth of the mine was reached.
v1.c12.s1.t3.6
The confined posture, the lack of fresh air and the excessive heat in which the labourers worked took heavy toll of human lives which were usually extinguished at the early age of 30-40 years.
v1.c12.s1.t3.7
The mines were worked only during eight months in each year beginning from October and the workings were suspended during the rains. Also the miners were obliged to work during the nights discontinuing their work early in the day for the excessive heat might otherwise be fatal. When the day work was completed the miners returned home with the proceeds of their labour which was collected at a public ‘cabūtra’ near the smelting furnace.
v1.c12.s1.t3.8
The ore was finely powdered using ‘ghuns’ or heavy hammers weighing 32 to 34 pounds (14.51-15.42 kg) each. The ore had to undergo hammering three times before it was fine enough for roasting process. The powdered ore was next mixed with cow-dung and made into rolls about 4 inch (10.16 cm) long which was dried first in the sun and then roasted in the open air in a fire of cow-dung cake. The ore was then ready for smelting.
v1.c12.s1.t3.9
For smelting ore the furnaces were built locally. The furnace was cemented with clay and the nozzles of the bellows were built up in it. The nozzles were earthen tubes which were thickest at the furnace end and at the top of the thick part there was a small air hole usually closed with a piece of wet rag but opened now and then to clear the tubes. The other end of the tube was fixed to the bellow. The bellow valve was formed by two sticks at the mouth, which were opened when the bag was raised for the admission of the air and closed when the bellows were pressed down. The upper part of the furnace was built with rings of fire-clay about 10 inch (25.4 cm) deep. The bellows were worked on three sides whilst the fourth side was the opening to the furnace, in which a plate of fireclay was placed, at the lower part of which was a hole for stirring the molten metal and to allow it to flow out.
v1.c12.s1.t3.10
After the furnace was lit, the roasted ore was gradually introduced alternatively with charcoal and a flux, called 'reet', the refuse from old iron furnaces.
v1.c12.s1.t3.11
In conclusion it will be pertinent to say that copper mining in ancient times was done in almost all the areas where present day mining is being done. The ancients had the skill to explore for the ore deposit and mine only such portions which would be remunerative. Mining was done by firesetting and quenching to initiate cracks in the orebody followed by extraction of ore with chisel and hammer. Transport of broken ore was done in baskets carried over the head of labourers. Ventilation at the working face was not systematically organised; for fresh air often the underground tunnels were connected to the surface by shafts. The mining depth was limited up to the water table.