EMPLOYEE WAS ESCORTING TWO MINE INSPECTORS TO UNIT 3. HE WENT TO THE SECTION BELT RECULATOR TO TAKE A READING. A ROOF ROCK MEASURING 6' BY 5' BY6"" THICK FELL FROM BETWEEN THE ROOF BOLTS STRIKI NG HIM ON THE BACK OF HIS LEGS KNOCKING HIM TO THE GROUND. HE SUSTAINED A SIMPLE FRACTURE AND SWELLING IN HIS LOWER LEGS.