Aug 26, 2021 · Bog ore is an ironrich sedimentary rock that was harvested locally from bogs and similar bodies of water. It was also found in fields and meadows that used to be bogs. Bog ore is often considerably less than 50% iron. The rest of the rock was made up of impurities that the workers had to remove. Gabbro was used as a flux;a way to purify the ore.