Special Kitty Cat Litter: 25lb bag
Ingredients: Ground Clay
I wasn't sure if this might take the place of turface or granite
I think it might be better if you posted this question in the Container Soil thread Al started. There already has been a lot if discussion about the pros and cons of various substitutes. If you haven't already read it, it's worth taking the time. See the link below. Plus there's a lot of photos there.
Here is a link that might be useful: Container soil and water retention
It might work as a substitute, as long as it holds up in certain tests. I've included a link with information on using cat litters and various products as turface substitutes. It should contain the information you're looking for.
Here is a link that might be useful: Cat Litter, Floor Dry, and Other Soil Componants...