Wisconsin Geological Natural History Survey » Mining: Iron
In Wisconsin, the most important iron ore minerals are oxides: magnetite (Fe 3 O 4), hematite (Fe 2 O 3), and goethite/limonite (Fe 2 O 3 •H 2 O). Brief overview of Wisconsin''s iron mining history. Limited amounts of highgrade iron ore were first mined in Wisconsin in the 1850s in the Black River Falls District of Jackson County and the ...