Banded-iron formation | rock | Britannica
Iron formations are typically Archean or Paleoproterozoic in age, with a significant decrease in iron formation deposition around 1.8 Ga following the Great Oxygenation Event (Bekker et al., 2014, Konhauser et al., 2017, Smith, 2018).A second major pulse of iron formation deposition occurred during the Cryogenian (e.g. Kirschvink, 1992), including the iron formations of the Kingston Peak .Iron ore: Rocky material from which metallic iron may be profitably extracted. Iron ore is usually rich in iron oxides such as magnetite, limonite, or hematite. Limonite: A brown-colored iron oxide ore formed by the weathering of iron-bearing minerals and mined for the production of iron.