A much more involved and comprehensive version of my bloomery building mod.

Features:
1) All technical "metal ores" are removed from the game and replaced with normal stone versions. This deactivates the automatically coded default smelter building reactions for anything except melting objects, and removes ores from embark previews (which is also more realistic). It also deactivates ore stockpiles, but you can just use "economic stone" easily as a replacement.
2) All metals that are redundantly pointless for the game or unrealistic for the 14th century are removed (platinum, aluminum, etc. see below), and a couple other realistic metals are added (arsenical bronze, arsenic)
3) The bloomery building replaces all iron and steel production. It realistically does not require flux, but does require much more manual labor and fuel than before, and the fuel must be charcoal only.
4) Various new reactions were added to the smelter building for all of the metals that are easy to smelt. You still use the same building as before.

Building - Bloomery:
14th century Europe did not have blast furnaces in any significant usage. They didn't melt iron at all, they got it hot enough to be spongy, then hammered it over and over (requiring re-heating) to physically knock out chunks of more brittle impurities while the iron folded and bent and stayed in the "bloom" of metal. Iron could then be used alone, or steel could be made by reheating bits of iron that had enough carbon with oxygen and more carbon, then welding them together and folding to remove more impurities and make into objects (or in this case just bars). Carburizing to make steel would have created significant waste as pig iron for metal that got too much carbon. They didn't have the technology to do anything with pig iron, so it is modeled as lost metal here.

Both iron and steelmaking therefore in this mod are hugely labor intensive compared to vanilla, however neither of them require flux (since hammering removes impurities instead). Flux is optional, and if you use it, you get to skip two of the hammering steps, but it can only play a minor role in bloomery forging at best. All fuel MUST be specifically charcoal. Charcoal is purer than mineral carbon in terms of impurities, and you have to work too hard to drive out impurities in bloomery forging to just add them back in constantly (you'd never achieve useful metal if you did).

Note: blooms are supposed to be semi-molten, and not allowed to cool. I roughly simulate this in the mod by giving them a fixed temperature above their heat damage point. If you leave them alone without working to the next step for ~2 weeks, they will self destruct. Working even just one step "resets the clock."

Iron Making
A] Ore -> Impure bloom -> quasi-pure bloom -> semi-pure bloom -> pure bloom -> 2 iron bars fuel: 3 charcoal per bar
B] Ore + flux -> semi-pure bloom -> pure bloom -> 2 iron bars fuel: 2 charcoal per bar (but 0.5 flux)

Steel Making
A] Ore -> Impure bloom -> quasi-pure bloom -> semi-pure bloom -> pure bloom -> 2 small steel blooms -> 1 large steel bloom -> 1 steel bar fuel: 9 charcoal per bar
B] Ore + flux -> semi-pure bloom -> pure bloom -> 2 small steel blooms -> 1 large steel bloom -> 1 steel bar fuel: 7 charcoal per bar (but 0.5 flux)
C] 2 iron bars -> 2 small steel blooms -> 1 large steel bloom -> 1 steel bar fuel: 10 charcoal per bar if inefficiently done from scratch, 4 charcoal per bar if from melted goblinite, etc.

Building - "Realistic Smelter"
Just a big furnace where you would melt things other than iron and remove slag impurities. Same concept as the vanilla DF smelter is supposed to be, except with all of the original's unrealistic abilities removed. All ores were made just normal stone, so the original smelter building has no reactions other than melting objects. Everything happens here, and all non-14th century metals are removed (except adamantium). Arsenical bronze is added, which is arsenic alloyed bronze that is significantly stronger, on par with regular iron (not steel). You can use non-charcoal fuel here, due to it being proper smelting, which is more forgiving than bloom hammering.

All other metal making:
Lignite and Bituminous are as normal
Silver nuggets -> 4 silver bars (can no longer make silver armor and weapons)
gold nuggets -> 4 gold bars
galena -> 2 lead bars (silver required different methods and would be lost in slag with just simple smleting)
galena -> 2 silver bars (if using silver methods, the lead is too oxidized to be useful as metal. One or the other)
cassiterite -> 4 tin bars (made more common)
sphalerite -> 1 zinc oxide boulder (distilled at still + 1 log + fuel to 4 zinc. Zinc sublimates to a gas, so you "roast" off other impurities first, then you literally distill it to pure metal)
malachite or tetrahedrite -> 4 impure copper bars (~30% weaker than normal copper)
native copper -> 4 pure copper bars
realgar -> 4 arsenic bars
orpiment -> 4 arsenic bars (both made a bit more common)
malachite or tetrahedrite + quartzite -> 4 pure copper bars (silica is a flux for copper ore.)
3 pure copper + 1 tin = 4 bronze bars
3 pure copper + 1 tin + 1 arsenic = 4 arsenical bronze bars (~40% stronger than bronze, on par with iron)
1 tetrahedrite + 1 tin = 2 arsenical bronze bars
3 silver bars + 1 pure copper bar -> 4 sterling silver bars
1 pure copper bar + 1 zinc bar -> 2 brass bars (worth as much as gold in this mod)
adamantine as normal

All other metals removed as too futuristic or redundant for gameplay (Nickel, platinum, bismuth, aluminum, billon, bismuth bronze, black bronze, electrum, various pewters, rose gold, pig iron)