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When the iron-bearing groundwater came into contact with more oxygen-rich groundwater, the reduced iron was converted back to insoluble iron oxide, which formed the concretions. [74] [75] [76] It is possible that reduced iron first formed siderite concretions that were subsequently oxidized. Iron-oxidizing bacteria may have played a role. [77]
The geology of the region is dominated by the Weches greensand, which consists of glauconitic sand and clay. This greensand is underlain by various sedimentary formations, including the Queen City sand member and the Sparta sand. The iron ore is typically found in the form of limonite, concretions, or thin lenticular beds within the greensand.
The fossiliferous concretions are found in the Mazon River area of Grundy, Will, Kankakee, and Livingston counties. Additional fossils are found in LaSalle County, Illinois; between the Vermilion River and Marseilles, Illinois. The ironstone concretions are recovered from exposures along streams, roadcuts and in active or abandoned coal mine areas.
The abundant concretions found in the Navajo Sandstone consist of sandstone cemented together by hematite (Fe 2 O 3), and goethite (FeOOH). The iron forming these concretions came from the breakdown of iron-bearing silicate minerals by weathering to form iron oxide coatings on other grains.
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.
Martian spherules (also known as hematite spherules, blueberries, & Martian blueberries) are small spherules (roughly spherical pebbles) that are rich in an iron oxide (grey hematite, α-Fe 2 O 3) and are found at Meridiani Planum (a large plain on Mars) in exceedingly large numbers.
Border wall materials were listed by Gov Planet last week at $5 as the minimum opening bid for 20 tons of steel bollards on an online auction site that advertised multiple lots.
Ferrous metals such as cast and wrought iron and steel usually corrode to form thick concretions that can entirely cover the metal object. [9] Corroded shipwreck artifacts that are made of iron may be conserved via electrolysis. Electrolysis is a method that uses an electric current to create a chemical reaction that cleans the object and ...