WHILE PREPARING TO LOAD EXPLOSIVES IN A DRILLED HEADING ROUND A ROCK APPROX. 2' X 2' FELL OUT OF THE BACK FROM BETWEEN THE ROOF BOLTS. THE BOLTS HAD BEEN INSTALLED ON A 3' X 3' PATTERN. THE RO CK STRUCK THE INDIVIDUAL ON LOWER HALF OF HIS LEFT LEG. A SMALL PIECE HIT HIM ON THE NOSE AND LEFT CHEEK.