If you can get it fine enough, and then add coarser amounts here and there as you can with ground foam, I don't see why you shouldn't do an experiment. The trick is to vary the texture to mimick nature. Texture and hues and colours, of course...shapes, too.
Larry- I have a stubborn streak and I think I'll try it just to see what kind of results I get.
I can spread it on the layout and vaccum it up if I don't like it.
Just another reason to procrastinate doing any serious scenery work.
Thanks to everyone for their comments.
Mikey