Järnnoduler
Järnnoduler, or iron nodules, are spherical or ellipsoidal concretions composed primarily of iron oxides and hydroxides that form in soils, sedimentary rocks and groundwater-deposited sediments. They range from a few millimeters to several centimeters in size, and are typically hard and rust-colored on weathered surfaces. Their interiors can be dense or show concentric layering around a nucleus such as organic matter or a mineral grain.
Formation occurs where iron-rich porewater or groundwater precipitates iron minerals as redox conditions shift, or where
Mineralogy is usually dominated by iron oxides and oxyhydroxides, such as goethite and hematite, with possible
Occurrence is widespread in temperate and tropical soils, as well as in river, lake and coastal sedimentary
Economic relevance is generally limited; iron nodules themselves are not typically mined as ore. However, larger