Many consumers, builders and even some tile installers share the mistaken idea that natural stone tile products may be installed on the floor in the same way as is ceramic tile. In most installations this is completely untrue and will many times lead to a very costly replacement.
Many of these folks will tell you they have installed stone tile on a single layer of structural wood subfloor and backer board for years without problems. The main reason this poor choice is promoted comes from the desire to have the stone tile floor installed flush to the adjacent floor finish. While this is a nice idea as far as the flush surface goes, it is really a recipe for failure for the stone tile.