I've wondered about that. I didn't think Fog rock occurred naturally. If not, then what is that?
I thought it was a naturally occurring cave and that the Isle was riddled with them. It would make sense why the Isle was a nature reserve in pre-Empire days. All those lovely caves would make No Man's Landing a destination for spelunkers. It wouldn't even matter that there were coal deposits in the caves since everything ran off of Aether.
Of course, this still doesn't explain the luminescent rocks.