One inherent problem with any course is that you can only be taught how to do something. Experience cannot be taught as most of you who have done a tiling course will understand. Think back to your first jobs and look at yourselves now.
The particular problem with any stone course is that there are so much Natural Stone out there it would be impossible to teach all of them on any course.
Wetdecs post stated that experience is the only route to this and he is absolutely correct. However, the principles can be taught and in my opinion this would take at least two weeks. In addition though it is very important that the potential candidate is "Au Fait" with natural stone formation and the differences between them. Another important factor is to have a very good understanding of sealers and the way they work.
I am off for a pint now so a bit more next time
Kev