So as far as interesting monsters go, the pebble gnome doesn't exactly rock. Sure it's got that crazy, squonk-esque magical resistance, but not much else. Perhaps the pebble gnomes' magical antipathy arises from a steady diet of teary-eyed squonk meat? Anyway, I'm sharing these grouchy little bastards with you because I especially like Don Turnbull's comments:
On the face of it, there seems to be no place for pebble gnomes in D&D -- they won't fight, have little treasure and won't go on adventures. Yet it is only reasonable that, in the course of adventuring, player characters will come across 'monsters' which have no particular function from time to time.