*£? Most clastic dikes in western coal mines are of a sandstone texture and can enter the coalbed from either the roof or the floor (30) , Geologic Factors in Predicting Coal Mine Roof-Rock Stability in the Upper Kittanning Coal- bed, Somerset County, Pa BuMines RI 8575, 1981, 41 pp 25 Bunnell, M D , C Kravits, and J Reese .