Not to overcomplicate an interesting subject.,but thought I would throw in a case study to ponder (see pix below). Just this morning, I looked at a small outside entry terrazzo step. It has marble or marble-like aggregate (maybe quartz-not sure). Much of the aggregate close to the walls and along the channel along the front have been washed away by rain. There are small black marble (or quartz?) mosaic squares set into the center spelling out the address. There are small cracks running through the surface. My best guess is to really start as low as possible on the grit scale, and use a combination of hand grinders around the edges and a floor machine up to 400, densify at 200, and powder polish. I would clean first with klenztone. Thought about using epoxy to fix cracks, but my concern is that they are stress cracks and may reappear. Am wondering, considering the condition, if Resin diamonds are strong enough or should I go to metals? some of the whiteness no doubt comes from road and sidewalk salt, so I would probably color enhance with enrich n seal or Lithofin color enhancer or similar. Any comments? Suggestions about metal diamonds?