Coal Mine Tours to some of the largest surface coal mines in the world are offered through the Gillette Visitor's Center at 1810 S Douglas Highway Suite A. The tours are offered Monday through Friday and are approximately 2 hours long they start at 9:00am or 11:00 am throughout the summer. The tour is $5.00 per person (cash or check only please). Please contact the Gillette Visitor's center to schedule your tour today. (307) 686-0040. 2019 tour dates. May 27, 2019 through August 30, 2019.