[ Black Hills Photo Gallery - Central Hills - Big Thunder Gold Mine ] The Big Thunder Gold Mine contains one of the largest collections of original mining equipment in the Black Hills area. The mine tour takes you on an adventure through mining history, geology, displays, and an opportuntiy to take home some gold ore. The Big Thunder Gold Mine is located near the town of Keystone on the way to Mt. Rushmore. It is open daily from the beginning of May to the middle of October. Web Site Looking back towards the entrance The end of the mine. The end of the mine. Strongbox - Secure gold tranport Ore milling equipment.