Editing Chromite (section)

== Distribution of deposits ==
[[File:Yukon chromite prospect.jpg|thumb|left|A chromite prospect in [[Yukon]]. The black bands are chromite, which also carries [[platinum group metals]]. Gray rock is bleached [[ultramafic]]s.]]
Chromite is found as [[Cumulate rock|orthocumulate]] lenses in [[peridotite]] from the Earth's [[mantle (geology)|mantle]]. It also occurs in [[Layered intrusion|layered]], [[ultramafic]] intrusive rocks.<ref>{{cite journal | doi = 10.1016/0892-6875(88)90045-3 | title = Chromite- mineralogy and processing | year = 1988 | author = Gu, F | journal = Minerals Engineering | volume = 1 | pages = 235 | last2 = Wills | first2 = B | issue = 3| bibcode = 1988MiEng...1..235G }}</ref> In addition, it is found in metamorphic rocks such as some [[serpentinite]]s.  [[Ore]] deposits of chromite form as early magmatic differentiates. It is commonly associated with [[olivine]], [[magnetite]], [[Serpentine group|serpentine]] and [[corundum]].<ref>{{Cite journal|last1=Emeleus|first1=C. H.|last2=Troll|first2=V. R.|date=2014-08-01|title=The Rum Igneous Centre, Scotland|journal=Mineralogical Magazine|language=en|volume=78|issue=4|pages=805–839|doi=10.1180/minmag.2014.078.4.04|bibcode=2014MinM...78..805E|s2cid=129549874|issn=0026-461X|doi-access=free}}</ref> The vast [[Bushveld igneous complex|Bushveld Igneous Complex]] of [[South Africa]] is a large layered [[mafic]] to [[ultramafic]] [[Igneous rock|igneous]] body with some layers consisting of 90% chromite, forming the rare rock type [[chromitite]] (cf. chromite the mineral and chromitite, a rock containing chromite).<ref>Guilbert, John M., and Park, Charles F., Jr. (1986) ''The Geology of Ore Deposits,'' Freeman, {{ISBN|0-7167-1456-6}}</ref> The [[Stillwater igneous complex|Stillwater Igneous Complex]] in [[Montana]] also contains significant chromite.<ref name=Klein/>

Chromite suitable for commercial mining is found in just a handful of very substantial deposits. There are 2 main types of chromite deposits: [[Stratum|stratiform]] deposits and podiform deposits. Stratiform deposits in layered intrusions are the main source of chromite resources and are found in [[South Africa]], [[Canada]], [[Finland]], and [[Madagascar]]. Chromite resources from podiform deposits are mainly found in [[Kazakhstan]], [[Turkey]], and [[Albania]]. [[Zimbabwe]] is the only country that contains notable chromite reserves in both stratiform and podiform deposits.<ref name="Prasad-2016">{{Cite book|title=Environmental materials and waste: resource recovery and pollution prevention|editor=Prasad, M. N. V. |editor2=Shih, Kaimin|isbn=9780128039069|location=London|oclc=947118220|date=2016-04-19 }}</ref>

=== Stratiform deposits ===
Stratiform deposits are formed as large sheet-like bodies, usually formed in layered [[mafic]] to [[Ultramafic rock|ultramafic]] [[Igneous rock|igneous]] complexes. This type of deposit is used to obtain 98% of the worldwide chromite reserves.<ref name="Duke-1983">{{Cite book|title=Ore deposit models 7 : Magmatic Segregation Deposits of Chromite|author=Duke, J. M.|oclc=191989186}}</ref>

Stratiform deposits are typically seen to be of [[Precambrian]] in age and are found in [[craton]]s. The [[mafic]] to [[Ultramafic rock|ultramafic]] [[Igneous rock|igneous]] provinces that these deposits are formed in were likely intruded into [[continental crust]], which may have contained [[granite]]s or [[gneiss]]es. The shapes of these intrusions are described as tabular or funnel-shaped. The tabular intrusions were placed in the form of [[Sill (geology)|sills]] with the layering of these intrusions being parallel. Examples of these tabular intrusions can be seen in the [[Stillwater igneous complex|Stillwater Igneous Complex]] and [[Bird River greenstone belt|Bird River]]. The funnel-shaped intrusions are seen to be dipping towards the center of the intrusion. This gives the layers in this intrusion a [[syncline]] formation. Examples of this type of intrusion can be seen in the [[Bushveld Igneous Complex]] and the [[Great Dyke]].<ref name="Duke-1983" />

Chromite can be seen in stratiform deposits as multiple layers which consist of [[chromitite]]. Thicknesses for these layers range between 1&nbsp;cm and 1 m. Lateral depths can reach lengths of 70&nbsp;km. Chromitite is the main rock in these layers, with 50–95% of it being made of chromite and the rest being composed of [[olivine]], [[Pyroxene|orthopyroxene]], [[plagioclase]], [[Pyroxene|clinopyroxene]], and the various alteration products of these minerals. An indication of water in the magma is determined by the presence of brown [[mica]].<ref name="Duke-1983" />

=== Podiform deposits ===
Podiform deposits are seen to occur within the [[ophiolite]] sequences. The stratigraphy of the ophiolite sequence is deep-ocean sediments, [[pillow lava]]s, [[Sheeted dyke complex|sheeted dykes]], [[gabbro]]s and [[Ultramafic rock|ultramafic]] [[tectonite]]s.<ref name="Duke-1983" />

These deposits are found in ultramafic rocks, most notably in tectonites. It can be seen that the abundance of podiform deposits increase towards the top of the tectonites.<ref name="Duke-1983" />

Podiform deposits are irregular in shape. "Pod" is a term given by geologists to express the uncertain morphology of this deposit. This deposit shows [[Foliation (geology)|foliation]] that is parallel to the foliation of the host rock. Podiform deposits are described as discordant, subconcordant and concordant. Chromite in podiform deposits form as [[Euhedral and anhedral|anhedral]] grains. The ores seen in this type of deposit have nodular texture and are loosely-packed nodules with a size range of 5–20&nbsp;mm. Other minerals that are seen in podiform deposits are [[olivine]], [[Pyroxene|orthopyroxene]], [[Pyroxene|clinopyroxene]], [[pargasite]], [[Mica|Na-mica]], [[albite]], and [[jadeite]].<ref name="Duke-1983" />