EE WAS CHANGING A BROKEN GUARD ON THE OFFSIDE/INBY END OF THE #5 BELT DRIVE TAKEUP. WHILE IN THE PROCESS A PIECE OF ROCK MEASURING 12"" X 14"" X 3"" SLID FROM THE RIB AT A DISTANCE OF 8"" STRIKING HIM ON THE BACK OF THE NECK. HIS TREATMENT CONSISTED OF A CONTUSION. RECORD OF EVENTS IS AS FOLLOWS: (1-17-02, SEEN DOCTOR), 1-18-02, INCURRED LOST DAY) (1-21-02, SCHEDULED TO RETURN, BUT DID