Age of coal deposits in India:
There are two age groups of coal deposits in India

1. Paleozoic / Gondowana Coal ~ 98% of total coal deposits in India
2. Cainozoic / Tertiary Coal ~ 2% of total coal deposits in India

Gondowana Coals in India:

About 95 % coal mining and production come from the Gondowana coal deposits in India and mainly used for electricity generation and metallurgical industries. The are a total of 14 different Gondowana coal basins in India spread over North-Eastern and Central eastern zones.

Major states in India with Gondowana coal deposits

• Bihar
• West Bengal
• Orrissa

Major Gondowana coalfields in India:

• Jharia
• Raniganj
• Bokaro
• Ramgarh
• Karanpura
• Singrauli
• Bisrampur

In addition to the coalfields listed above, there are many other coal fields in the same region producing good amount coals.

Range of seam thickness of Gondowana coals in India:

• 1 to 30 m ( Note: There is one exceptionally thick coal seam – 134 m discovered at Singrauli coalfield)

General structural features of the Gondowana coal fields:
In general, there are several fauls in the Gondowana coalfields, though the coals are not very much techtonized.

General Nature of coals at Gondowana Coalfields at India:

• High to low volatile bituminous coals with high ash content. Sulful content varies within various seams and coalfields.
• Cocking coal – good quality coking coal is produced at Jharia and Raniganj.
• The Pench – Kanhan – Tawa coalfields in central India also produce Gondowana coals. These coalfields are free from stuctural disturbances. The coal is high volatile non-coking bituminous coal.

Tertiary coals in India
North- Eastern and North -Western parts of India also have brown Tertiary coals. Also, at southern india, there is a very important lignite deposit at Neyveli.

Range of seam thickness of Tertiary coals in India:

• 1-33 m

General structural features of the Tertiary coal fields:

• Highly techtonically disturbed.
• Located in the mountaneous regions of northern India
• Lenticular at Assam coalfields

General Nature of coals at Tertiary Coalfields at India:

• Sub-bituminous to high volatile bituminous at Makum Coalfields in Assam.
• Lignite in Southern India (Neyveli) with high sulfur content.

Tertiary coal in India also locally used for electricity generation.

Reference: Handbook of Practical coal Geology by Larry Thomas

 Additional Reading

• History of coal mining in India
• Buy Coal Reserve Maps India
• A detailed report on Coal Mining India with various policy/act regarding coal mining
• Check out coal reserves in various
  
• Website of Coal India Ltd

Coal Mining in India : Source

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Coal Reserve in Various cities in India : Source