Just a few ideas for the general expansion of the game because I feel the industry aspect of it is somewhat neglected.
- Meteoric iron: basically a boulder that, when chipped, would have a 20% chance of dropping q20-q30 iron (at max Industry) instead of stone. They'd serve as a source of iron and q>10 stone for hearthlings without decent access to a mine or minehole, and be low-hanging fruit at the beginning of a world that people can fight over and cause drama. Or maybe you can make a statue or obelisk out of them, I don't know. Comes in two variants, small (moveable) and large (unmoveable). Of course, they'd have to be extremely rare, and this would be extremely unfair for players who don't live near one, but whatever, life is unfair anyway.
- Lead: could appear in veins, but could also show up occasionally as a byproduct of smelting copper and silver ore. Since it'd be abundant and easy to work with, it could be used where any other common metal would do, e.g. in mine supports, cauldrons, or in the construction of stone mansions. It could also have unique applications such as bullets for slings (which function in the same way that arrows do by adding damage based on projectile quality) and maybe some fishing lures. Also, just for shiggles you could craft cups out of them which also add 1-2 hurt FEPs whenever you drink from them, I don't know. Regardless, it'd still be more useful than (pure) copper is now.
- Mercury: could be used as an additive to ore smelters to facilitate the process of extracting silver and gold ores, making the process more efficient than it would be just by setting the slider to full Industry (though it would have to be rare in itself). It could also be used to make a few curios too, I guess.
- Platinum: kind of ahistorical (as it wasn't really discovered outright until a few hundred years ago), but it would be a nice "prestige" metal to be sought after and could be used to make a variety of Symbel items and pieces of jewelry. It would have to be extremely rare, occurring only in tiny veins on the bottom two layers or very rarely appearing in smelted copper ore. Edit: actually, scratch this (graying out because this forum has no strikethrough feature).
Meteoric iron would just serve as a way to get more metal and decent stone circulating around, or otherwise be a prize to fight over which always makes things interesting. Lead and mercury were well-known substances in antiquity, and any advanced Iron Age society with mining capabilities would have found them eventually. As far as platinum goes, well, who doesn't love things that glitter. Pretty much every other metal we know about wasn't discovered until around the Enlightenment or later, so those couldn't be added into the game.