We have a slate floor in our half bathroom downstairs. When our boys were little, the kept missing the toilet and spraying the slate floor with urine occasionally. I didn't know it was happening at the time, so the slate is permanently damaged. I have tried numerous times to take lemon oil and let it sit on the etched spots on the floor. It seems to work- I wipe off the excess and shine up the floor-only to see that the spots are still there. I hope I have described the problem so that you can understand what I am dealing with. Does anyone know what else I can try?