Apr 08, 2013· Iron Ore – Mining Artifacts. The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite, limonite or siderite. . Most large hematite iron ore deposits are sourced from metasomatically altered banded iron formations and rarely igneous . The very finely dispersed iron content, present as magnetite, is generally 25 to 30%.