THE SECONDARY RETURN CHUTE WAS PLUGGED WITH A BIG ROCK. THE EMPLOYEE WAS USING A 3 LB HAMMER TO BREAK THE ROCK OUTSIDE OF CHUTE. HE QUIT AND WAS DIGGING OUT WITH HIS HAND AND I WAS ON THE OTHER SIDE OF THE CHUTE DIGGING ROCKS OUT. HE PICKED UP THE HAMMER AND SWUNG NOT KNOWING I HAD A HOLD OF THE ROCK HE WAS GOING TO HIT AND SMASHED THE MIDDLE FINGER OF THE RIGHT HAND.