Figure 27. Photographs of a core-drilling rig and a collected core. A, A truck-mounted, mobile, core-drilling rig on location in the process of collecting core of the Upper Freeport coal bed in western Pennsylvania. Photograph by R.W. Stanton (U.S. Geological Survey). B, Coal core, 3 inches in diameter, from a coal bed in the Powder River basin, Wyoming. The white material beneath the core is plastic tubing used to collect the core and prevent it from falling apart. The upper half of the tubing has been removed to provide access to the coal. Photograph by P.D. Warwick (U.S. Geological Survey).