When an acidic substance, such as lemon juice or cleaning products, comes into contact with calcite or other minerals in stone that are sensitive to acid, a damage called etching occurs. Because of the dull whitish marks that are left behind, etches are often mistaken for a stains or watermarks, but etching is actually a chemical reaction that roughens the surface of your stone.
Very mild etching can sometimes be removed with a polishing powder. Deep etch removal, however, should only be accomplished by a professionally trained stone restoration contractor. Either way, it would be best to contact us, because the last thing you want is to cause additional damage to your natural stone.