MINER WAS REMOVING A 6"" ROCK FROM SELF-CLEANING TAIL PULLEY. THE ROCK WAS ELONGATED & WAS STUCK WITH ONE POINT ON THE PULLEY & THE OTHER CREATING TENSION ON THE BELT. AS THE MINER TOUCHED THE ROCK WITH A STEEL BAR, THE ROCK CAME LOOSE & THEBELT SNAPPED UP AGAINST THE PULLEY, PULLING UP ON THE END OF THE ROD INSIDE & LEVERED IT DOWN ONTHE OUTSIDE END CAUSING HIM TO HURT HIS ARM.