A ROOF FALL OCCURRED AS THE MINER WAS GETTING FRIRST LIFT OUT OF BLOCK #19 IN #4 ENTRY. THE ROCK FELL ON CONVEYOR BOOM CAUSING CAR STOP TO DIG INTO BOTTOM. THE FALL MEASURED 3'THICK X 20'LONG X 20'WIDE. NO VENTILATION WAS DISTURBED, NO INJURY OCCURRED, AND THE FALL WILL NOT BE CLEANED UP.