Which of the following rock systems provides over 90% of the coal in India?

The correct answer is D) Gondwana system. Most of India's coal, roughly 90 per cent or more, comes from Gondwana rocks, which are Permian to Triassic in age. Lower Gondwana coal fields such as Jharia, Raniganj, Bokaro and Karanpura lie in the Damodar valley, and Singareni lies in the Godavari valley. Coal here formed from glossopteris-type vegetation in a warm, humid, post-glacial phase.

• Vindhyan system is a Proterozoic sedimentary sequence. It gives sandstone, shale and limestone, and the Son valley is known for building stone and cement, not coal.
• Dharwar system is Archaean and metamorphosed. It hosts iron ore, manganese, gold and schist, and has no significant coal.
• Tertiary system does contain coal, but mainly lignite, as at Neyveli, in Assam and at Palana in Rajasthan. Its share of India's coal is small, so it cannot be the answer.

Core concept: Gondwana coal is the backbone of India's thermal power and steel sector. This links directly to Mains questions on energy security, coal block allocation after the 2014 Supreme Court verdict, and the environmental cost of mining.

Trap: Aspirants pick Tertiary because they remember lignite is a coal. The question asks about the rock system providing the bulk of coal, and that is Gondwana.