EE WAS PULLING A SMAPLE OF COARSE MATERIAL THRU A CLAMSHELL ON THE END OF A DISTRIBUTION PIPE IN THE SIZING AREA. HE WAS HOLDING THE CLAMSHELL OPEN WITH HIS RIGHT HAND AND APPARENTLY PLACED HI S LEFT HAND INT HE OPENING. HE ATTENTION WAS DIVERTED AND HE LET THE CLAMSHELL CLOSE ON HIS HAND. HE INSTINCTIVELY PULLED HIS HAND OUT AND RECEIVED AN AVULSION BETWEEN THE KNUCKLE AND THE ARE