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The above classification scheme is the most commonly used and accepted, though sometimes an older system is used which divides iron-rich sedimentary rocks into three categories: bog iron deposits, ironstones, and iron formations. A bog-iron deposit is iron that formed in a bog or swamp through the process of oxidation.
Ironstone (sandstone with iron oxides) from the Mississippian Breathitt Formation, Mile Marker 166, I-64, Kentucky. Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially.
Metamorphic rocks are created by rocks that have been transformed into another kind of rock, usually by some combination of heat, pressure, and chemical alteration. Sedimentary rocks are created by a variety of processes but usually involving deposition, grain by grain, layer by layer, in water or, in the case of terrestrial sediments, on land ...
Iron oxides are derived from mafic igneous rocks and other iron-rich rocks; bauxites are derived from granitic igneous rock and other iron-poor rocks. [15] Nickel laterites occur in zones of the earth which experienced prolonged tropical weathering of ultramafic rocks containing the ferro-magnesian minerals olivine , pyroxene , and amphibole .
The following is a list of rock types recognized by geologists.There is no agreed number of specific types of rock. Any unique combination of chemical composition, mineralogy, grain size, texture, or other distinguishing characteristics can describe a rock type.
Jasper is the main component in the silica-rich parts of banded iron formations (BIFs) which indicate low, but present, amounts of dissolved oxygen in the water such as during the Great Oxidation Event or snowball earths. [16] The red bands are microcrystalline red chert, also called jasper.
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There is uncertainty on how to translate the proper name Omarolluk (and omar rocks). According to the records of the Canada Centre for Mapping and Earth Observation Natural Resources, the features Omarolluk Sound and Omarolluk Formation were named after Omarolluk, an Inuk man who accompanied and guided R. J. Flaherty on numerous geological surveys of the Belcher Islands and elsewhere in the ...