I'm not sure how the "Viewing ore while in a smelter" rumor got started but I'm about 99.99% sure that the ONLY time the Nature/Industry slider plays a role is the instant the ore is created in the mine.
Also, not that it's really important, but you can hold shift while holding a piece of coal and it will add the next piece directly to your cursor so you don't have to keep picking them up. You can ctrl-click the stone directly from the smelter to throw them on the ground instead of putting them in your inventory first. Finally, it might be a good idea to mention that the stones you get from failed metal attempts retain the Quality that the metal would have been so they are used for crafting higher quality stone axes.
All in all, good job.