Mineral Resources of Assam - Coal : Assam Geography Study Materials & Notes
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Mineral Resources of Assam – Coal: Assam Geography
Assam occupies a very significant place in the map of mineral wealth of the country, but Assam is lagging far behind the other states in the matter of proper exploitation of such wealth. Out of the different types of mineral wealth, only four types of mineral wealth, only four types, namely coal, oil and gas, limestone, quartz and clay are being exploited at present.
Coal in Assam
Coal in Assam at present occurs in the district of Dibrugarh, Sibsagar, Tinsukia and Karbi Anglong (Erstwhile Mikir Hills). Due to the bifurcation of Assam most of the coalfields of Garo Hills have gone to the newly state of Meghalaya. In undivided Assam, the most attractive coalfields belong to the Eocene and Oligocene age.
(i)The Lower Eocene of the Garo and Karbi Anglong Hills,
(ii)the Middle Eocene of the Karbi Anglong, and
(iii)the Upper Eocene to Oligocene of the Naga Hills,etc.
The discovery of Coal in Assam took place when the administration of the province was taken over by the British Government. The coal of the Naga Hills near Borhat in Sibsagar district and Jaipur in the present Dibrugarh district was reported by Mr. Jenkins in the year 1838. Coal also reported to have occurred in the Karbi Anglong Lunglai areas. The occurrence exposes a 3.64m seam dipping 12 to 20 degrees to the north-west.
The Coal has overage 4 to 5 per cent moisture, 50 to 57 per cent volatile matter, about 25 per cent volatile matter, about 25 per cent fixed carbon and between 13 to 20 per cent ash,which is very resinous (high volatile matter)type of coal or lignite. There are also records of coals of better quality within 12 miles (19.30 km.) of Lumding. It is stated that coal is also found in the Namber area within Sibsagar district. In the Nazira area with in the same district the coal mines of Borjan and Kanjan (now in Nagaland) have been worked by Messrs. Shaw Wallance and Company. The Nazira coal-field is partly drained by the Saffrai river, which exposes coal measures with in 5 miles (8kms) of Saffrai station. Some of the coal from the Nazira coal-field is among the best in India .Analysis showed that the coal contain 4 to 10 per cent moisture, 36 to 44 per cent volatile matter,under 1 to 4 per cent ash.
Northward from the Disang river at Namrup the coal measures extend north-eastwards into Lakhimpur (undivided).The Jaipur coalfield is now in the present Dibrugarh district and marks the southwestern end of the richest coal-bearing strata (Tikak Parbat Formation) of Upper Assam,which extends onwards beyond Lakhimpur (undivided)into the frontier tract beyond the Tirap river and on to the Namphuk river. Coal fields are also there at Mergherita and Makum areas. All the coal mining operations in the Makum and the Margherita north-eastwards area is conducted by the North Eastern Coal Fields, Coal India Ltd. In succession from the west, the collieries of Margherita area are Namdang, Bargolai, Tikak, Ledo, Lakhapani and Tipong quarry. Mr. G.E. Hines,Geological expert states that the coal measures (Tikak Parbat formation)are of Oligocene age. The thickness of the seams and the excellence of the coal must be unique in India. But the Coal which occurs in the Tikak Parbat Formation of the Barail Group is conducted under many difficulties where the worst natural conditions in India have to be faced. The bottom of 120 metres of this formation is very carbonaceous and includes one seam in the Makum Coalfield varying in thickness from 18 metres to nearly 30 metres and another six metres thick besides a number of thinner ones. The coal-bearing horizon to the south-east of the Makum Coal field is of great areal extent as revealed in the oil wells drilled at Naharkatia and Rudrasagar.
In the Makum coal field alone the reserves have been estimated at 1,000 million tons. The reserves estimated in the Namphuk area is 600 million tons. The hard coke formed in the Makum coal, being high in Sulphur is not used as a
metallurgical coke for iron smelting Sulphide ores such as the lead, Copper and Zinc ores of Upper Burma, and the Sulphur could be recovered as Sulphuric Acid. In both the low and the high temperature carbonisation the Gas must be excellent calorific value and therefore useful as fuel in itself.
Among all the districts of Assam, the present district of Tinsukia has huge deposits of coal in comparatively young Tertiary rocks. But the presence of the injurious constituent sulphur and the inaccessibility of the coal fields have impeded large scale exploitation upto Miobum in Arunachal Pradesh. In Dibrugarh and Tinsukia districts, coal exposures are found in the Jaipur, Namdang and Ledo areas upto Tipang river. In all cases, the workable coal seams are exposed along the northern flank of the Naga-Patkai Ranges facing Sibsagar and Lakhimpur (undivided) districts. It has been stated earlier that individual coal seams vary in thickness at places from 3.04m to 18.28m. Recently, a 3.04m thick coal seam has been encountered in the Assam Oil Company’s first bore hold at Naharkatiya at a depth of little less than 3048m. The coal is of good quality. The district of Sibsagar is also rich in respect of coal mines. It is mainly mined in Nazira coal field. Coal is also found in the Jhanji and Disoi rivers. The seams in both these cases are few, thin, and highly inclined. The coal have 3.4 per cent to 6.8 per cent moisture, 4.8 to 6.5 per cent ash, 33.8 per cent to 36.9 per cent volatile matter and 52.9 to 54.9 p.c fixed carbon.
The Nazira coal field is nearly twenty-five kilometres long and situated about six kilometres south of Naginimara railway station upto the Dihang river. But except for a small outcrop of coal measures within eight kilometres of Saffrai railway station, the coal field lies in Nagaland.
In Jaipur outcrops of the seams are seen along a strip of forty kilometres long, about half of which lie in Dibrugarh district. A thickness of more than 13.71m of coal in six seams is exposed in the Dilli river. The coal-bearing rocks dip to the east with a high degree of inclination (30o to 80o) on the Sibsagar side the coal is worked out by the Dilli Collieries (Assam) Limited. The Colliery has an area of four square miles (10.36 Sq. Kms.),which was closed in June, 1970.
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