EMPLOYEE WAS STANDING ALONG SIDE THE MINER OPERATOR'S COMPARTMENT OBSERVING ROCK BEING CUT & LOADED OUT FROM AN OLD ROOF FALL AT #8 WALL, #1 NORTH MOTHER BELT. THE HEAD OF THE MINER CAUGHT A 5'DRILL STEEL THROWING IT BACK & IT STRUCK HIM ON THE RT. FOREARM & UPPER ARM CAUSING A FRACTURE TO BOTH THE ULNA & RADIUS BONES.