Tamil Nadu has the largest reserves (resources) in India of:

Tamil Nadu holds the largest share of India's lignite resources, roughly three-quarters of the total. The main deposits are in the Neyveli area of the Cuddalore district, with others in the Mannargudi area (Thanjavur and Tiruvarur districts) and Ramanathapuram.

About lignite:

• Lignite, also called brown coal, is a low-grade coal with high moisture and low carbon content.
• It is geologically young (Tertiary age), much younger than India's main Gondwana coal.
• Because of its moisture and tendency to catch fire in storage, it is usually burned in power stations near the mines (pithead plants).

Neyveli:

• Lignite was discovered at Neyveli in the 1930s-40s, reportedly when a farmer found black material while digging a well.
• NLC India Limited (formerly Neyveli Lignite Corporation), a public sector company under the Ministry of Coal, was set up in 1956.
• It operates large open-cast lignite mines and thermal power stations at Neyveli, which supply electricity to Tamil Nadu and other southern states.
• Neyveli is also a planned industrial township.
• Mining problems at Neyveli include pumping out large quantities of groundwater from the mines (the lignite lies under a pressurised aquifer), land acquisition and displacement of farmers.

Other lignite deposits of India:

Rajasthan: Barmer, Bikaner (Barsingsar and Palana) and Nagaur districts. Rajasthan has the second largest resources.

Gujarat: Kutch (Panandhro), Bharuch and Bhavnagar districts.

Jammu and Kashmir and Puducherry also have some deposits.

Other minerals of Tamil Nadu:

• Tamil Nadu also has limestone (for cement), magnesite (around Salem), garnet and other beach sand minerals, and graphite.
• Salem has the Salem Steel Plant (SAIL), which produces stainless steel.

Why not the other options?

• ✗Bauxite resources are largest in Odisha.
• ✗Chromite is concentrated in Odisha's Sukinda valley.
• ✗Manganese resources are largest in Odisha, while Madhya Pradesh leads in production.