Black limestone looks like a polished stone that has been partially bush hammered (photos don't do it justice its a right mess) and if you already think it looks like a mess its worse in real life! Laid badly nice lips on it and acid etched to kingdom come and the icing on the cake is its scratched nicely and they stick out beautifully as its a black tile. Some tiles have a grey washed out look. Customer will not have it ground down and you would lose the textured effect if you did. My thoughts are Clean it, hone it with powder to try and get an even starting point across the entire floor then a fine grit flexible pad, polishing powder and a colour enhancer to try to hide some of the worst scratches and darken the tile down again. Might get an improvement but the scratches will not go. Any advances on that.