THE F6 LONGWALL SECTION WAS DOWN AT START OF SHIFT FOR A BROKEN DOG BONE AT TAILGATE. INJURED ATTEMPTED TO CROSS BETWEEN 191 AND 192 SHIELD AND A PIECE OF STONE 6"" TO 8"" THICK 18"" WIDE AND 37"" IN LENGTH FELL OUT FROM BETWEEN THE SHIELDS AND STRUCK HIM ON TOP OF THE RIGHT FOOT.