Stone to Iron Upgrade - Qelifern/IronFurnaces GitHub Wiki

This upgrade will transform a standard vanilla stone furnace into an iron furnace. Simply shift + right click on the block with the item in hand and transformation should be instantaneous. If you happen to craft this upgrade with the FastFurnace mod installed it will not work. However, you can drop this item on the ground, together with a single cobblestone and get your iron back.

Recipe

*This recipe will accept any form of cobblestone