Be careful with boiling natural stones. Depending on the rock, some do better than others however the real issue is often times natural rocks have cracks in them and it is possible to damage a stone like that.

As far as using water on an oiled stone it depends how porous the rock is and how long it was used. A non porous rock you should be able to get the surface oil off. If its porous and had heavy use you will have more problems.