EMPLOYEE WAS GREASING THE JAW ON CRUSHER, KNEELING DOWN. A METAL BAR USED TO LOOSEN JAMMED ROCKS WAS STORED AT THE TOP OF THE CRUSHER, AND IT FELL APPROX 12 FT AND STRUCK EE ON THE BACK OF HIS HEAD, KNOCKING HIM TO THE GROUND. EE WAS WEARING ALL REQUIRED PPE (I.E. HARD HAT).