A piece of draw slate fell from between installed roof bolts approx. 4 rows outby the last row of roof bolts. The slate measured 54"" long, 32"" wide and 0"" to 6"" thick. The mining height was around 8.5'. Employee was standing alongside of the bolter machine; the draw slate struck his hard hat, middle back, left shoulder, left arm and drove him into bolter. His chest was bruised.