Joining a certain branch that you are not even interested in just for the IIT tag is not the most logical decision. One usually decides on a certain branch for 3 reasons; either to get a good package or to pursue your area of interest or to follow the majority. However, in the case of Mining Engineering, this is not the case at all. You won’t be available to avail either of these benefits because of its low demand. In fact you will end up with the following circumstances

• You will have to work extremely hard in the first year in order to get a branch change
• In case you are unable to get a branch change, you will start running after POR, join different clubs to work on your non Engineering abilities.
• During placements you will be more inclined towards Non-Core placements because of your aversion to Mining.

Still, if you are adamant about getting into IIT, then join only if 

• You want to work in analytics, consult or analyst after 4 years instead of Engineering 
• If you want to pursue MBA from an IIM
• If you want to switch your field after graduation.

The reason why I am suggesting you give up Engineering is that with Mining, you can literally pursue anything other than Engineering. So it’s better you make up your mind for the same or apply to other institutes.