EE REPORTED HE WAS SITTING BEHIND THE ROOF BOLTER TO EAT WITH HIS BACK AGAINST THE RIB WHEN A PIECE OF ROCK FELL FROM BETWEEN THE RIB AND THE ROOF BOLT OVERHEAD. IT STRUCK HIM PRIMARILY ON THE KNEES AND WAS DESCRIBED AS ABOUT 18"" SQUARE BY 1-2"" THICK. HE WAS TAKEN TO THE E.R. WHERE NO FRACTURE WAS FOUND.