My front hallway (1950's ranch) has a 6 x 12 foot section of irregular slate tiles. I am trying to fix things up prior to putting the house on the market and have thoroughly cleaned the grout, which makes everything look much better. However, several of the tiles either have chips with missing pieces or else a section (looks like someone dropped something heavy on it) with many cracks and missing pieces. Any suggestions on how to repair this? I would rather not get into trying to remove and replace one of the slate pieces.