On the markets there are lots of different black and they name it shanxi black. You might encounter the same problems how to distinguish the dyed black from the natural one. The straight way is to check the color shade as the natural one will have the pattern while the dyed doesn’t. One another way is to check the sawn side. Make the sawn side wet and then compare the sawn side with the polish one then you will know the answer. The simplest way is to spray the water on the polish surface. If the material is waxed or dyed, the water will stay on the surface.