THE CONVEYOR CHAIN ON THE HIGHWALL MINER HAD BROKEN. THE INJURED & A CO-WORKER WERE ATTEMPTING TO REPAIR THE CHAIN & WHEN THE CO-WORKER HIT A CHAIN LINK WITH A SLEDGE HAMMER, A PIECE OF THE CHAIN FLEW OFF BECOMING EMBEDDED IN THE INJURED'S LEFT CHEST JUST BELOW THE COLLAR BONE. INJURED WENT TO A MEDICAL FACILITY TO HAVE METAL REMOVED & RECEIVED 2 STITCHES.