ok... but for my personal knowledge, 'flux stone' is only a concept from DF, right? I don't find anything short of DF when typing flux stone...
So, within the concept of DF, a flux stone is a stone that has a variable amount of iron, correct?
flux stone is the stone that's used to extract carbon from iron alloys. IRL it's chalk or limestone idk if someone really ever used valuable marble for it.
It was actually used in steel-making technology (not now, now we have bessemer process).
i guess this link has some info on it:
http://en.wikipedia.org/wiki/Smelting#Fluxes
EDIT: flux stone is calcium carbonate CaCO2 in its various forms. it does not contain any iron but is usefull when you have to reduce the amount of carbon in iron alloys
Both lime and aluminum were used in the melt shop I worked at back in the late 1990's. It was a recycling facility, not a ore processing utility - the scrap was loaded with impurities because, well, it was scrap. I wasn't on the melt crew, I was on the maintenance crew, but we used lots of lime, and a couple bars of aluminum in every melt. There were also other materials used to get the chemistry of the steel right before it was poured into billets.
Here's a good article about the EAF process:
http://en.wikipedia.org/wiki/Electric_arc_furnaceOur dwarves, are both making steel from iron, and recycling steel, so lord only knows what processes they are using
I think it's safe to say though that they are not using electric arc furnaces, though they might be using a similar acting process, chemically.