Hello Harshit, first of all congratulations on getting such a good score in GATE. You can actually assess your chances of getting into IITs or NITs by considering previous year's cut offs of mining engineering.

Following are the top colleges providing the course of your choice.
So you can check the previous year's cut off trends of the colleges that provide mining engineering through the following links:
1. IIT, Kharagpur
https://engineering.careers360.com/articles/gate-cutoff-for-iit-kharagpur
2. IIT BHU, Varanasi
https://engineering.careers360.com/articles/gate-cutoff-for-iit-bhu
3. IIT, Dhanbad
https://engineering.careers360.com/articles/gate-cutoff-for-iit-dhanbad
4. IIEST Shibpur
https://engineering.careers360.com/articles/gate-cutoff-for-iiest-shibpur
5. NIT Surthkal
https://engineering.careers360.com/articles/gate-cutoff-for-nit-surathkal
6. NIT Rourkela
https://engineering.careers360.com/articles/gate-cutoff-for-nit-rourkela
7. VNIT Nagpur
https://engineering.careers360.com/articles/gate-cutoff-for-vnit-nagpur
8. NIT Raipur
https://engineering.careers360.com/articles/gate-cutoff-for-nit-raipur

So these are the only IITs and NITs that offer M.Tech courses in the specialisation of your choice.
In order to have a look at some more prospects, or the colleges that you can get other than the above mentioned colleges, visit;
https://engineering.careers360.com/colleges/list-of-engineering-colleges-in-India?f%5B0%5D=sm_college_degree%3AM.E%20/Mtech.&f%5B1%5D=sm_course_offered%3AMining%20Engineering&f%5B2%5D=sm_quali_exam%3AGATE

Also you can use to the college predictor , to get some more accurate predictions about the colleges you can get. Check the link given below:
http://bit.ly/2J9S0MN

All the best!
I hope this helps.