I've used this on our slate floor with great results! If you decide to try it - do it carefully and thoroughly, and don't overlap anywhere. I used washing-up sponges and put exactly the same amount of liquid on each time (by tipping the bottle up and back quickly and making a 'dot' of it, same amount of times) and did exactly the same amount of tiles with each 'load'. I really enjoyed doing it, don't know why!! It was so satisfying to look back at the floor looking lovely. It protects it too, and makes it easier to clean. One bottle was plenty, too.
If it helps anyone else, a friend of mine has done the same on quarry tiles - proper, expensive ones - and is just as pleased as I am!!
(Follow the instructions on the label for preparing area first. Did my floor when it was new and still perfectly clean.)