Love that black finished Crack. Woodworking has been my main hobby for years and I have had good luck at ebonizing oak and ash with a simple process. Obtain some black dye from a woodworker’s store, a water or alcohol base dye works equally well, but may have to re-sand if the water base raises the grain. Apply 2-4 coats of dye, let it set for at least a day then apply a standard black stain (like Minwax ebony). As a finish coat rub in some Tried & True varnish oil, the more coats you add the glossier it gets. Adding the standard black stain helps pop the grain and give it an ebony like appearance.
Jim G.