The secret of the art of healing fractures in the cab with epoxy is to shape your stone and semi-polish it. To get rid of that nasty crack, heat the stone to 200 degrees in an oven. Mix epoxy and apply to one edge of the crack. Gradually apply resin, working from one end of the crack to the other. THIS IS IMPORTANT! You will notice that the epoxy becomes very liquid when it touches the hot stone and it flows right into the crack. By applying the epoxy at one end and working toward the outside edge of the cab, the air is driven out and the epoxy replaces it. Then put the stone back in the oven and let it remain there for another 20 minutes. By this time, the epoxy will harden. Scrape off the surface and proceed with final polish. If you do this right, the fractures will be nearly impossible to detect.