No matter what you call it, it is all the same; damage to a natural stone from acidic liquid exposure, be it food grade or chemical. Calcium based stones such as Marble, Quartzite, Limestone, Travertine, and Onyx are the stones that are susceptible to etching. An etch mark is not a stain, it is an actual chemical reaction that takes place in the stone causing the surface to dull. Etching can be classified into three categories; Minor, Moderate, and Severe. A minor etch results only in a loss of shine. No roughness can be felt on an area with a minor etch mark.