40d:Flux

Stones which are classified as flux materials can be used in the creation of pig iron and steel at a smelter. They are considered economic stones, and so can be manipulated on the z-stone menu. All flux has a material value of 2, which is twice that of common stone (material value 1), making it preferable for workshops, construction, and most all stone products. (Only obsidian and some higher-value ores have a higher material value for stonework.)

Note that blocks made out of flux materials cannot be used in the production of pig iron or steel.

The following stones fall under this reaction class:

• Calcite
• Chalk
• Dolomite
• Limestone
• Marble

All flux stones form layers or (for (calcite) are present as inclusions within them, and so can be seen in the pre-embark screen. Limestone, dolomite and chalk form sedimentary layers, which can have large deposits of iron-bearing ore. Marble is a metamorphic layer, so it can be found within almost any biome. Most significantly, marble can be found near igneous extrusive layers (i.e. near volcanoes and magma vents), which is rare for any sedimentary layer*.

^{(* What this means is that it's very unusual for a map to have all three of magma, flux and high-iron-bearing sedimentary layers together. It can happen, and larger maps increase the chances of such, but it's unexpected when found close to each other.)}

Trading for flux

If your map has no flux on it (which is a common situation), then you can request it from the dwarven traders (assuming the traders have access to flux, which is not guaranteed*). Make sure you order (flux material) stone, which is in the material section, since you can't use flux blocks to create steel.

(* And there is no way to determine this ahead of time, not until the dwarven liaison arrives to take your order for future caravans.)

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See also:

• steel
• pig iron