…  said. The MSHA identified the bulldozer operator as Mike Wilt, 37, and the backhoe operator as Dale Jones, 52. The section of …  high wall collapsed at the Tri-Star Mining Inc. site near Barton, about 150 miles west of Baltimore. The cause of the collapse is …

…  venture at Superior, attracting special attention, said Mike Barton, director of the Institute for Mineral Resources at the University of …