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Depending on the environmental conditions present at the time of their formation, concretions can be created by either concentric or pervasive growth. [11] [12] In concentric growth, the concretion grows as successive layers of mineral precipitate around a central core. This process results in roughly spherical concretions that grow with time.
Similar to the marine nodules, concretion layers are defined based on iron and manganese content as well as their combination. [2] High iron content nodules appear a red or brown color, while high manganese content appears black or grey. [2] The dominant metal oxide is related to the elements enriched in the nodule.
Iron is stored in many organisms in the form of ferritin, which is a ferrous oxide encased in a solubilizing protein sheath. [ 10 ] Species of bacteria , including Shewanella oneidensis , Geobacter sulfurreducens and Geobacter metallireducens , use iron oxides as terminal electron acceptors .
Bog iron is a form of impure iron deposit that develops in bogs or swamps by the chemical or biochemical oxidation of iron carried in solution. In general, bog ores consist primarily of iron oxyhydroxides , commonly goethite (FeO(OH)).
While, for the large majority of the allowable compositions, the iron oxide contents in the spherules were between 85 wt% and 96 wt%; further, the nickel content was always close to 0.3 wt%, a group of five standard oxides (MgO, Na 2 O, P 2 O 5, SO 3, and Cl) each had content above trace-level with a combined group content of 6.8 +/- 2.4 wt ...
They described it as a dark-gray shale, fossiliferous, with veins and seams of gypsum, and concretions of iron oxide. The Pierre Shale is about 3,138 feet (956m) thick at the type locality. It overlies the Niobrara division and underlies the Fox Hills beds. [1] It was named for an occurrence near Fort Pierre on the Missouri River in South ...
Banded iron formation from the Barberton Greenstone Belt, South Africa. A typical banded iron formation consists of repeated, thin layers (a few millimeters to a few centimeters in thickness) of silver to black iron oxides, either magnetite (Fe 3 O 4) or hematite (Fe 2 O 3), alternating with bands of iron-poor chert, often red in color, of similar thickness.
Fenton's reagent is a solution of hydrogen peroxide (H 2 O 2) and an iron catalyst (typically iron(II) sulfate, FeSO 4). [1] It is used to oxidize contaminants or waste water as part of an advanced oxidation process. Fenton's reagent can be used to destroy organic compounds such as trichloroethylene and tetrachloroethylene (perchloroethylene).