Here coal occurs in association with limestone and shale’s of cither Eocene or Oligocene- Miocene periods. The coal deposits of Assam, Meghalaya, Nagaland, Arunachal Pradesh and Jammu-Kashmir belong to this category.
Makum coalfield of upper Assam in Dibrugarh district is the most important coal producing region of the state. It has 6 coal seams of which the basal seam is 18 m thick. Workable seams are exposed along the northern flank of the Naga-Patkoi ranges facing Sibsagar (at Nazira) and Lakhimpur (at Jeypore) districts.
A three meter thick good quality coal seam has been discovered at Nahorkatiya at a depth of 3,050m. Other coalfields of the state include Doigrung, Nambor and Longoi. Assam coal has high coking qualities with very low ash contents. But high sculpture content makes it unsuitable for metallurgical purpose. It is well suited to hydrogenation process to produce liquid fuels. The estimated total reserves are 2,952 million tones.
In Meghalaya coal deposits occupy the areas in United Khasi Jaintia and Mikir hills and include the closely associated Balyong, Doigring and Waimong coal-fields lying east of the Senisang Valley. Longoi field with an area of 51.7 sq km contains a coal reserve of 81 million tones. Pendengru coalfield with eight seams has a reserve of 32 million tones of good quality coal. Other minor coalfields are Pynursla, Mawlong, Sheila, Cherrapunji and Bapung. Meghalaya coal with estimated reserve of 4,594 million tones contains 5.84% of moisture, 35.16% of volatile matter, 8.6% of ash, and 50.40% of fixed carbon.
The state has a total coal reserve of 902 million tones. Main coal-fields include Namchick- Namphuk (Tirap) with reserve of 91 million tones, Abor hills; Miri, Daphla, Aka hills and Miao Bum (reserve 6 million tons).
Nazira, Janji, Disai and Barjan are important coalfields of Nagaland.
jammu and kashmir
These coal deposits also belong to the Eocene period with their occurrence in Punch, Riasi and Udhampur districts. Important coalfields include Kalakot, Mohogala, Metka (western Chenab region), Ladda and Saugar Marg (eastern Chenab region). The coal has low percentage of fixed carbon and high moisture content. It is highly friable and pyrites. Recently anthracite coal has been discovered in the Riasi area of Jammu but its mining is economically not viable.
Coal has also been located in Chauri, Laharu, Gadhsan and Samet areas of Chamba district in Himachal Pradesh.
Lignite is a low grade inferior coal containing too much of moisture and low percentage of carbon (35-40 per cent). When exposed, it disintegrates easily. Drying and briquetting are, therefore, necessary before it is put to use. It is mainly used in thermal power plants and as industrial and domestic fuel. It is also used for carbonisation and fertilizer production. Lignite deposits are located away from traditional coal mining areas and, hence, play vital role in substituting coal, saving coal transport cost and promoting economic development in these areas.
In Kerala lignite occurs in 45-65 cm thick bands near Varkala (Thiruvananthapuram district), Paravur (Kollam district), Pathirapalli (Alappuzha district) and Cannanore (Kannur district). It is also found in Kozhikode district. Most of the deposits are in the form of peat with very low carbon content.
Lignite deposits are found in Kachchh (Umarsar, Lefri, Jhulrai and Baranda) and Bharuch districts with estimated reserve of 1.5 million tones. Except at Umarsar the coal is of poor quality with 5.55-10.6% of moisture, 38.18-52.96% of volatile matter, 9.40-45.4% of ash and 7.74-37.74% of fixed carbon. The total annual production was 49.41 lakh tones in 1997-98.
jammu and kashmir
Lignite deposits are found in the Raithan and Lanyalab basins of the Shaliganga area, in Karewa beds south-west of Srinagar-Badgam area and the Nichahom area near Handwara (Baramula district). The Nichahom area has estimated reserve of 21.68. Million tones. The composition of lignite includes 15% moisture, 28% volatile matter, 27% fixed carbon and 30% of ash.
Traces of lignite deposits have been found at Bahur, Araganaur and Kanniyankonil areas. The composition includes 16.28% of moisture, 38.55% of volatile matter, 37.72% of fixed carbon and 7.45% of ash content. Scattered deposits have also been found at Padukaddai, Vadapuram. Kadavanur and Palaiyam areas.
Small deposits of lignite are also traced in Jainti and Buzahill area of Jalpaiguri and Darjeeling districts. Beds of lignite also occur in the Ganga delta area.