Physics for Cultural Heritage : Need of the future generations
- Part 1 -

Dr Md Raheijuddin Sheikh *

Iron Smelting found in Wollega, Ethiopia

The two hour long oral history of the People's Museum Director Shri M. Gourchandra on the iron smelting work by the ancient people at Kakching was recorded without any cuts except one small break at the time of changing the cassettes. Many models are displayed in the Museum. I took some shots of the model of the furnace, samples of the iron extracted in traditional styles and techniques by the ancient people, the equipment used in the smelting and the bellows and pipes etc used for the purpose.

I was quite busy that night on playing, rewinding and forwarding the camera print on my handicam. My next job was to find out a way how the Indirect Narration of Oja Gourachandra could be produced in the form of the direct speech. I thought of visuals, I thought of inserts, I thought of the animation, I thought of the realities and so on. The night has passed sleepless. In the meantime, I came to remember the reports from one of my students who was staying at the Boys' Hostel. One day, he talked about some iron smelting sites near his village.

The following day, the 6th November, 2008, I took a trip for a brief survey of a number of iron smelting sites around the village of Kakching. I took my student too in the trip. On the way, he was always telling about Laimanai village, about 50 kilometres from the capital city of Imphal. Without killing much time here and there, we rushed the spot.

While searching for some iron smelting sites around the village of Laimanai, my eyes suddenly caught with the beautiful greenish colour of the dense bush of standing sugarcane crops. That was a pretty small hill at a distance of about 20 kilometres from Kakching and about 40 kilometres from the Indo-Myanmar border. I was surprised to see the surface of the area covered by full of iron slag!

The site which is locally known as Tumu Ching (Tumu Hill) to the local people is famous for ancient iron smelting. At a height of about 776m above the sea level, Latitude 24° 28'38" N and Longitude 93°57'28" E, the small hillock which covers an area of about 0.5 Km2 revealed plenty of iron slag of the sizes ranging from the size of small peanuts to the lumpy size of big rocks of dimensions measuring about 30 cm × 50 cm. The discovery created a new beginning of scientific research on cultural heritage in the north eastern part of the country.

When interacted with the oldest ever living person who is also the chief of the nearby village, I came to know that some people from Tumu, now in Myanmar came and practised the iron smelting. The remains of the iron extracts in large number of huge lumps were known to the people by the local name Yotthi, which means iron slag.

The hill boasts of the rich standing sugar crops. Of course, there might be some reasons. The soil containing iron slag must be suitable for the sugar crop plantation. The owner has rightly chosen the crop for the soil repeatedly for many seasons and over many years. When I made my own way by negotiating the dense bush of the sugar cane plants, I found it so difficult to see the world outside rather than the surface with full of slag.

I asked the watchman how the hill was covered with such slag. He replied, "The place remained covered with such slag which they called yotthi, since time immemorial. The hillock was known as Tumu Ching simply because the people from Tumu now in Myanmar crossed the series of mountain ranges in search of iron ores and settled there to undergo the work of smelting. However, it remained in complete darkness how the place had been covered with such a huge amount of slag. It was by the blessings of God that a plenty of iron was gifted to that specific area".

He could also make no mention about the period during which the people from Myanmar came and extracted iron from there. He told that the hillock was purchased by a moneylender from the then chief of the village. It had been utilised for growing sugarcane as the soil of yotthi was found favourable for the crops. The service of keeping the field as watchman continued down from his forefathers. He could see no other crops than those standing sugarcanes since he took the charge of the watchman just after the death of his father.

From the historical records it is known that king Khuiyoi Tompok (154-264 CE) founded the iron deposits at Kakching area. He ultimately, established an iron smelting colony at Kakching. However, no mention is made in the Royal Chronicles about any other places around the Indo Myanmar borders as we could see in the case of Tumu Hills. The People of Kakching knew only the iron smelting places in their locality and did not mention about such other places in the neighbouring villages.

But, the wide spread use of iron during the ancient period as evident from the historical records suggests that apart from the iron smelting colony that had been established at Kakching during the chieftainship of Lord Khamlangba, iron might have also been smelted in any other areas in the south eastern part of Manipur.

When investigated further, I could establish that a big furnace might have been constructed at the top of the hillock. This is quite hypothetical because many loose slags of bigger sizes were found deposited near the bottom of the hill. These heavier lumps of slag might be rolling down from the top when the furnace was gradually demolished by the cultivators in grounding the surface for growing sugarcane cultivation. I excavated from the top a few metres deep under the ground to find some remains of the furnace.

However, neither the furnace nor the slag was found under the ground. From that work of investigation it can be concluded that most of the slag which was deposited near the furnace had been broken into pieces while grounding the surface and the bigger lumps that could not be broken into pieces were rolling down to the bottom of the hill as they are much heavier than the soil of the place.

During excavation just below the surface two large pieces of slag that formed the ancient furnace could be found. The curvature of the sample gives the approximate size of the furnace. A layer of sediment, a few mm in thickness was attached to one such piece. The age of the archaeological slag was determined by dating the baked sediment by thermoluminescence techniques.

The characterisation of the slag by Optical Microscopy (OM), X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR) Differential Thermal Analyser (DTA), Scanning Electron Microscopy (SEM) and X-ray fluorescence (XRF) techniques are also documented.

The slag collected from the iron smelting place was washed with water in a tub. This removed the outer soil from the slag. It was washed again with water in another tub to extract the soil which was not exposed to sunlight. The soil so extracted was treated with 30% Hydrogen Peroxide (H2O2) to remove organic materials contained in the soil, 10% HCl to remove carbonates. Finally the soil was treated with dilute HF for about 30 minutes and then, with concentrate HF for another about 40 minutes to extract Quartz contents.

Characterization of iron and its slag obtained from various parts of India has been well documented. The chronology of early age iron smelting technologies is also documented. The Dhatwa iron was found to be produced through small crucible type furnace where limonite type ore was reduced. The slag obtained from such sites was found to be fayalite (SiO3 Fe). However, there have been no reports on iron slag samples found in Manipur.

The dating of the slag was carried out by using thermoluminescence (TL) dating technique. The slag has been characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Differential thermal analysis (DTA) and Optical microscopy which is supported by the Scanning electron microscopy (SEM) and corresponding Energy dispersive analysis.

The scanning electron microscopic investigations were carried out in a mineral liberation analyzer (MLA) of JK tech, Australia, in the Physics laboratory of the Institute of Material and Mineral Technology (IMMT), Bhubaneswar. The Mineral Liberation Analyzer (MLA) is an automated mineral analysis system that can identify minerals in polished sections of drill core, particulate or lump materials, and quantify a wide range of mineral characteristics, such as mineral abundance, grain size and liberation. Mineral texture and liberation potential are fundamental properties of ore and drive its economic treatment; the data gathered by the MLA is therefore invaluable to geologists, mineralogists, and metallurgists for process optimization, mine feasibility studies and ore characterization.

Commercially available since 2000, the MLA is being used by leading international resource companies to improve the processing efficiency of copper, nickel, lead, zinc, manganese, iron ore, mineral sands, and precious metals such as platinum, palladium, silver and gold. Its ore characterization capabilities are also used very effectively to evaluate exploration targets.

To be continued....