EE WAS WAITING ON HELPER TO SPOT A BOLT BEFORE ENTERING #2 LEFT TO BOLT WHEN A 12"" BY 12"" PIECE OF ROCK FELL BETWEEN BOLTS STRIKING OPERATOR ON THE HARD HAT BOUNCING OFF OF HAT STRIKING HIM IN THE RIGHT FOREARM CAUSING A LACERATION ABOUT 4"" LONG ON ARM. RECEIVED 17 STITCHES.