Flux

Stones which are classified as flux materials can be used in the creation of pig iron and steel at a smelter. All flux has a material value of 2, which is twice that of common stone, making it preferable for workshops, construction, and almost 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