I am not familiar with the environmental laws in India but in Canada you are often on the hook for closing down and cleaning up a site once it is abandoned (that is, you can't just walk away from it). My understanding is this can cost hundreds of thousands of dollars.

I recently met someone who was leasing oil wells (edit: natural gas, not oil) that lacked sufficient pressure to pump gas into a pipeline. The wells still had enough pressure that you could use them as an immediate fuel source so they were hooking up a few cryptocurrency mining rigs to a generator there. Apparently the companies who own the wells like this because they don't immediately have to declare the wells abandoned and pay the cleanup fees.

Since the government of India is setting targets for net coal export, you'll likely have to meet output quotas. So, good luck! :D

The mines probably come with liabilities of all sorts.

That does sound like fun but I'm sure there's a minimum bid.