Bog iron

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Bog iron refers to impure iron deposits that develop in bogs or swamps by the chemical or biochemical oxidation of iron carried in the solutions. In general, bog ores consist primarily of iron oxyhydroxides, commonly goethite (FeO(OH)). It was discovered during the Pre-Roman Iron Age, and most Viking era iron was smelted from bog iron.

Iron-bearing groundwater typically emerges as a spring. The iron is oxidized to ferric hydroxide upon encountering the oxic environment of the surface. Bog ore often combines goethite, magnetite and vugs or stained quartz. It is not clear whether the magnetite precipitates upon first contact with oxygen, then oxidizes to ferric compounds, or whether the ferric compounds are reduced when exposed to anoxic conditions upon burial beneath the sediment surface and reoxidized upon exhumation at the surface.

In colonial New Jersey bog ore was mined and refined and used for production of tools, wrought iron rails (many of which still grace stairs in Trenton and Camden) which do not rust like modern iron alloys. During the American Revolution the iron was used for cannon balls for the American forces.

In an episode of the TV program The Worst Jobs in History, presenter Tony Robinson was shown searching for bog ore.

See also

• Limonite
• Iron ore
• Ore genesis
• Acidithiobacillus ferrooxidans (iron oxidizing bacteria)
• History of ferrous metallurgy

• Talzhemir's Bog Iron Page
• Bog Iron Industry in The Pinelands, New Jersey

• ironfurnaces.com - a free wiki dedicated to the preservation of iron furnaces
• Bog Iron Formation in the Nassawango Watershed, Maryland U.S. Geological Survey: Open-File Report 03-346