EAST MAINS. THE JOB TASK WAS TO CHANGE A HEAD- JACK ON MINER AND THE HEAD OF THE MINER NEEDED CRIBBED BEFORE WORK STARTED. THE EMPLOYEE FINISHED BUILDING THE CRIB AND WAS WALKING AROUND THE HEAD OF THE MINER. A SHARP ROCK APPROX. 2""THICK X 4"" WIDE X 18"" LONG FELL FROM BETWEEN A BOLT & THE RIB. THE ROCK SLID DOWN THE EMPLOYEE'S ARM AND CUT HIS RIGHT HAND.