RAISE MINER WAS DRILLING OFF A ROUND. WHEN COLLARING A HOLE ON BACK A 1-2LB.PIECE OF ROCK FELL OFF BACK, NEAR COLLAR AND BOUNCED OFF ALIMAK RAIL. THE ROCK THEN STRUCK EE'S RT. HAND CUTTING TH E SKIN AT THE BACK OF HIS THUMB AND CUTTING A TENDON TO THE THUMB.