[villagetinker]

IMHO, I would be very careful of the new surface, if it is brittle, the crack will probably reappear in a short time. Out neighbors had a finish that looks like lots of pieces of different colored slate. When I asked them about the cracks coming back they told me that if that happens the installers come out and make the crack look like a mortar joint. As mentioned above, for minor cracks, I would use a flexible filler (silicone based, paint-able), and then repaint the area. If you are after a more permanent fix, you may need to have tile (wet location finish) with a crack isolation barrier installed. Hope this helps, send me a PM if you want more info, my step son does this type of work.