So I'll admit, some of the odd behavior I've noticed may be a result of f'ing around with saves and scenarios due to issues I introduced into my game at world-gen which has now led me to just trying to set up a scenario where I skip past the very early game, but when is ore generation on subsurface layers done?
I've noticed a couple of different times now that if I deplete a surface deposit before traversing down, there either is no deposit at the location, or that I've revealed a little prior figuring I'll excavate the rest later, only to come back and find that nothing else is being revealed when I bore into the tunnel walls around what I'd have assumed should've been a more substantial deposit (I still haven't used the surveyor as there doesn't seem to be a path to unlock it? Although the function of the device would assume the ore should already be present before I uncover it) Also, gotta mention, you work fast, I've had a game running since I woke up today, and you already fixed the surveyor tech tree issue.
So if I burrow down another layer, is it going to base the ore deposits off the surface, or the layer directly above it?