Our Advanced Metal Science

Archaeological evidence suggests that metallurgy was a very advanced science in Bharatiya civilisation. The mining of metals have been going on even before the protohistory
The purity of the metals like iron, copper, silver, lead, etc. obtained from wherever the evidence of ancient civilisation have been unearthed in our country, such as Nalanda, Harappa, Mohenjo-Daro, Lothal, Takshshila, Dholavira, Surkotada, Dayamabaag and Kaalibangan is 95 to 99 per cent. How could have this been possible? It is a riddle as to how our ancestors did have the technique to process the metals in such a pure form 4000 to 4500 thousand years ago.
 A view from Hatti Gold Mines
Bharat was earlier known as Sujalam Sufalam. This country was full of resources. We have learned in the school that smokes of gold and silver emanated from our country. There was certainly a lot of gold and silver in our country. Many foreign travellers have recorded that gold and silver were sold like vegetables in the market of Hampi during the Vijayanagar Empire. If we go a little further, when Allauddin Khilji attacked Devgiri for the first time, a defeated Ramdev Raya gifted him few manns of pure gold. It means that metals like gold, silver, copper, zinc etc. were known in our country since ancient times and they were processed as well.
Interestingly, how many people might know that the most ancient gold mine in the world that is still in use today is in Bharat? The mine is called ‘Hatti’. It is located in Raichur district of the north-eastern part of Karnataka. When Dr Rafter from Australia carried out carbon dating on two wooden pieces found in the mine in 1955, it was found to be about 2000 years old. But this mine may be even older. Even today the mine excavates gold by the name of ‘Hatti Gold Mines Limited’.
The uniqueness of this 2000-year old mine is that it has been dug 2,300 feet deep. Now, how could have this excavation been carried out? The scientist says that the mining was done with the fire setting style. It involves heating the internal rocks with the help of wooden fire and cooling them suddenly by pouring water on them. Cracks appear in big rocks through this process, and they break out.
Skandagupta, gold dinar, c. 455-467. The 8.40gm gold coin is representative of the prosperity in the Guptan Age  
A 650-foot deep vertical shaft was found in the same mine that shows our ancient skills in the mining sector. The kilns to obtain iron and their technology were available aplenty in those times. We have discussed the iron pillar near Qutub Minar at Delhi in the article ‘Iron Pillar’ in this series. Today, at least 1500-2000 years have passed to that iron pillar, but there is not a shred of corrosion to that pillar. And today even the 21st Century scientists wonder how this naturally corrosion-resistant iron was made.
Similar to this iron pillar is a 7-feet high Buddha idol completely made of copper. The idol is from the 4th century and is currently kept in London’s British Museum. The speciality of this idol found in Bihar is that the copper in it does not get spoiled. It remains ever shining.
An archaeologist named Rakesh Tiwari had excavations in the Ganga valley just recently. He found in it that India knew the technology to purify iron at least 2800 years ago. Of course, it could be earlier also. But evidence from about 4,800 years was found.
Local Refractories and Mines
Many refractories producing iron/steel in pure form in 300 years BC have been found in Dakshin Bharat. Later, the British named them Crucible Technique. In this method, pure malleable iron is taken in a vessel along with coal and glass and the vessel is heated so much that iron melts and absorbs carbon. The Arabian fighters later came to call this high-carbon iron as ‘Faulad’.
The book Rasaratna Samuchchay of Vagbhatta describes many types of kilns. He has described the kilns like Mahagajput, Gajput, Varahput, Kukkutput and Kapotkut. It tells about the number of cow dung cakes that are fed to kiln and temperature created in proportion to them. For example, 2,000 cow dung cakes were needed for Mahagajput kiln while Kapotkut that ran on low temperature needed just eight cow dung cakes.
These kilns based on cow dung cakes may appear very old and outdated concept for someone in today’s era of furnaces. However, the same kilns produced many things like an iron pillar and today’s scientists have failed to produce them even by using modern technology.
Bharadwaj Muni has described 532 types of structures similar to the fan of ironsmith in his book Brihad Vimanshastra. The iron for the Damishk sword, famous in history, would go from India. Many foreign travellers have noted that highly pure zinc and copper were made in India.
The copper is being used in India since ages. Evidence has been found that copper was used 300 to 400 years BC in India. Harappan era copper utensils have been found in excavations at several places, including Mohenjo-Daro. References and evidence have been found that many copper mines existed in the Baluchistan province in today’s Pakistan. References are found at many places that Khetri in Rajasthan had many copper mines.
How many of us might know that even the substance zinc was discovered in Bharat? The evidence has been made available that zinc was used in Rajasthan in the ninth century BC. More importantly, oldest mine of zinc known to history exists in Bharat, in Rajasthan.
This ancient mine of Zinc is in Javar village. The mine, which is about 40 km from Udaipur, produces zinc even today. At present, zinc is excavated here by ‘Hindustan Zinc Limited’. It is said that this min at Javar was in operation in the 6th century BCE. Evidence to that effect has been found. The process of making zinc was also very skilful, complex and technological. Indians had acquired proficiency in the process. Nagarjuna, who later wrote Rasaratnakar, has given a detailed procedure to prepare zinc. He is found to have described the methods of distillation, liquidation, etc.
In this method, the zinc ore taken out from the mine is melted at an extremely high temperature (more than 1000 degrees Celsius). The vapours emanating from this process are distilled. It is cooled, and the solid zinc starts to form through it.