EE WAS USING A SLATE BAR TO BREAK UP A LARGE LUMP OF COAL AT THE HEAD ROLLER AREA OF THE CRUSHER BELT. THE ELECTROMAGNET FOR PICKING UP METAL TRASH WAS ENERGIZED. EE GOT THE SLATE BAR TOO CLOS E TO THE MAGNET AND THE MAGNET PULLED THE BAR SMASHING THE LEFT THUMB OF EE BETWEEN THE BAR AND THE MAGNET. EE SUFFERED A LACERATION OF THE LEFT THUMB RECEIVING 7 SUTURES TO CLOSE.