HE STATED THAT THE A-FRAME BELT WAS CURLED UP UNDER THE CHUTE. HE HAD CO-WORKER TURN BELT ON/OFF TO SEE IF IT WOULD UNCURL, WHILE DOING SO, ROCKS START FLYING. HE THREW HIS HANDS UP TO COVER F ACE. HIS GLOVE ON RIGHT HAND HIT BELT CLAMP AND CAUGHT HIS HAND.