Iron ore
From Cantr II Wiki
Made by crushing either hematite, magnetite or taconite on either a stone table or work bench using either a type of hammer (stone, bronze or regular hammer) or a type of sledgehammer (sledgehammer or bronze sledgehammer). Please note that you can't do any work on a sledgehammer project with a hammer and vice versa.
Used to make iron in a smelting furnace or primitive smelting furnace.