While i agree in principle, i will remind you that our Moderate Success harvest moon turned a grand total of 6 figurines from bone to obsidian. While it would make sense to have worsening materials be a lot easier than improving them, and we don't need to literally turn all the stone into sand, that is at least a couple orders of magnitude more stuff, and we'd have a penalty to effectiveness for being outside of our influence range and its possible that she'd get a generic influence check to defend against it.
Also, i'm actually not sure how much this arctic society has access to/uses stone...
@Powerofmind can you give us a general description of how our people live? Like...what are their houses built out of? What sort of setup do their villages have? Aside from fishing and hunting walruses and hte like, what all do they do? how artic-y is our island? Do they ever see grass? or even dirt? Or is it all snow/ice/etc?