The roads are made from 'hypertufa'. It's a mixture of cement, sand and perlite. It's used in making garden ornaments (if you Google on the word hypertufa you get some examples).
I've got the idea for using this after seeing some incredible work from a guy named 'graniteshop' on the old G-Scale-Mad forum. Ufortunatly that forum is gone...
Carl, you are right. On the hill are laying some H0 scale tracks (Roco new silver) as a test.
I put them there last september and they have been out all winter, including rain and snow. They still are in perfect shape. I'm thinking of perhaps making a very narrow gauge (Gn15) line on the hill (just a circle around the rocks). On the other had, it looks very much like what it is...H0 track. So I'm also considering other options for alternatives for the track using techniques like these used on the Sandstone and Termite layout
So all ideas on tracks are welcome!