EMPLOYEE STATED THAT HE JUST RETURNED FROM LUNCHAND WAS ASSISTING THE ROOF BOLT CREW BY PREPARING BOLTS. WHILE MAKING UP BOLTS ON THE OPERATOR'SSIDE OF THE ROOF BOLTER TOWARD THE CONTROLS ON T HE FRONT, A PIECE OF OF ROCK APPROX 1"" THICK 27"" BY 52"" FELL AND STRUCK HIM ON THE HARD HAT SLIDING DOWN HIS RIGHT ARM AND STRIKING HIS RINGFINGER ON THE RIGHT HAND. HE WAS WEARING GLOVES.