[apache]

Well, by definition, rock is ice, a solid form of some silicate most likely. The truth is that ice planets are really planets that have things normally not frozen on Earth that are frozen on that planet. Ammonia, Methane, water, etc. are all stuff that is normally seen unfrozen on earth and most other planets in the system. But ice planets for whatever reason have these gasses/liquids actually frozen to, and acting as the surface. Europa has an ice surface, and some form of liquid ocean underneath. Under that, of course, is a solid basin of some sort.