Friends,  this holey rock is part burned coal and part scoria.  Masses like these are prevalent and scattered throughout an area where a coal vein was burning in the recent past.   They resemble lava formed from volcanic activity and are highly vesiculated (new word for the day).  Walking the higher ridges around the coal vein area, great areas of the plains have sunk away as a result of the underground clay shrinking in the intense heat. The burned coal is a gray color and sometimes is tightly bound to the adjacent scoria as seen in this image. til Tomorrow MJ