A. Coal ("Black Gold"):
Formed from prehistoric plant matter carbonized under immense pressure and heat over geological eras:
- Anthracite: Highest quality coal; $>90\%$ carbon content; hard, lustrous black, burns with a smokeless blue flame with maximum heat; leaves minimal ash.
- Bituminous: Most abundant commercial coal; $70-80\%$ carbon; dense black; primary coking coal for smelting iron in blast furnaces.
- Lignite (Brown Coal): Lower grade; $40-55\%$ carbon; high moisture; mined at Neyveli in Tamil Nadu for thermal electricity.
- Peat: Earliest, lowest stage of coal formation; $<40\%$ carbon; high moisture, produces dense smoke and low heat.
- Major Indian Coalfields: Jharia, Bokaro (Jharkhand), Raniganj (West Bengal - oldest coal mine), Singrauli (MP/UP).
B. Petroleum ("Liquid Gold"):
- Hydrocarbon liquid trapped in dome-shaped anticlines and fault traps of sedimentary rocks, formed from decomposed marine microorganisms.
- Refined via Fractional Distillation into petrol, diesel, kerosene, jet aviation fuel, LPG, paraffin wax, and bitumen asphalt.
- Major Indian Oilfields: Digboi (Assam - oldest oilfield in Asia, drilled in 1889), Mumbai High (offshore drilling platform *Sagar Samrat*, $160\text{ km}$ west of Mumbai in the Arabian Sea; produces over $60\%$ of domestic crude!), Ankleshwar (Gujarat).