INJURED AND 3 CO-WORKERS WERE IN 3900 NEW FOLD DECLINE LOADING DEVELOPEMENT ROUND. AS INJURED W AS BENT OVER CLEANING MUCK FROM THE BOTTOM RIGHT SIDE HOLE A PIECE OF LOOSE APPROXIMATELY 6"" X 6 "" X 3"" FELL FROM THE UPPER RIGHT SIDE WALL AND STRUCK INJURED ON THE BACK OF HIS HARD HAT. HE RECIEVED A 4"" CUT TO THE BACK OF HIS HEAD THAT REQUIRED STITCHES.