Editing Nickel (section)

===Occurrence===
{{See also|Ore genesis|Category:Nickel minerals}}
[[File:Widmanstatten hand.jpg|thumb|left|[[Widmanstätten pattern]] showing the two forms of nickel–iron, kamacite and taenite, in an octahedrite meteorite]]
Nickel ores are classified as oxides or sulfides.  Oxides include [[laterite]], where the principal mineral mixtures are nickeliferous [[limonite]], (Fe,Ni)O(OH), and [[garnierite]] (a mixture of various hydrous nickel and nickel-rich silicates).<ref name="Mudd 2010 pp. 9–26">{{cite journal |last1=Mudd |first1=Gavin M. |title=Global trends and environmental issues in nickel mining: Sulfides versus laterites |journal=Ore Geology Reviews |date=October 2010 |volume=38 |issue=1–2 |pages=9–26 |doi=10.1016/j.oregeorev.2010.05.003 |bibcode=2010OGRv...38....9M }}</ref> Nickel sulfides commonly exist as solid solutions with iron in minerals such as  [[pentlandite]] and [[pyrrhotite]] with the formula Fe<sub>9−x</sub>Ni<sub>x</sub>S<sub>8</sub> and Fe<sub>7−x</sub>Ni<sub>x</sub>S<sub>6</sub>, respectively. Other common Ni-containing minerals are [[millerite]] and the [[arsenide]]  [[niccolite]].<ref>[http://www.npi.gov.au/substances/nickel/index.html National Pollutant Inventory – Nickel and compounds Fact Sheet] {{Webarchive|url=https://web.archive.org/web/20111208083730/http://www.npi.gov.au/substances/nickel/index.html |date=December 8, 2011 }}. Npi.gov.au. Retrieved on January 9, 2012.</ref><ref>{{Cite web|title=Nickel reserves worldwide by country 2020|url=https://www.statista.com/statistics/273634/nickel-reserves-worldwide-by-country/|access-date=2021-03-29|website=Statista}}</ref>

Identified land-based resources throughout the world averaging 1% nickel or greater comprise at least 130&nbsp;million tons of nickel (about the double of known reserves). About 60% is in [[laterites]] and 40% in sulfide deposits.<ref name="USGSCS2019">{{cite web|first = Peter H.|last = Kuck|publisher = United States Geological Survey|title = Mineral Commodity Summaries 2019: Nickel|url = https://minerals.usgs.gov/minerals/pubs/commodity/nickel/mcs-2019-nicke.pdf|access-date = March 18, 2019|archive-url = https://web.archive.org/web/20190421125020/https://minerals.usgs.gov/minerals/pubs/commodity/nickel/mcs-2019-nicke.pdf|archive-date = April 21, 2019|url-status = live}}</ref>

On [[geophysics|geophysical]] evidence, most of the nickel on Earth is believed to be in Earth's [[outer core|outer]] and [[inner core]]s. [[Kamacite]] and [[taenite]] are naturally occurring [[alloy]]s of iron and nickel. For kamacite, the alloy is usually in the proportion of 90:10 to 95:5, though impurities (such as [[cobalt]] or [[carbon]]) may be present. Taenite is 20% to 65% nickel. Kamacite and taenite are also found in [[nickel iron meteorite]]s.<ref>{{cite journal|title = Trace element partitioning between taenite and kamacite – Relationship to the cooling rates of iron meteorites|last1= Rasmussen|first1=K. L.|last2= Malvin|first2=D. J.|last3= Wasson|first3=J. T.|journal=Meteoritics |volume= 23|date = 1988|pages = a107–112 |bibcode= 1988Metic..23..107R|doi = 10.1111/j.1945-5100.1988.tb00905.x|issue = 2}}</ref>

Nickel is commonly found in [[iron meteorite]]s as the alloys [[kamacite]] and [[taenite]]. Nickel in meteorites was first detected in 1799 by [[Joseph Proust|Joseph-Louis Proust]], a French chemist who then worked in Spain. Proust analyzed samples of the meteorite from [[Campo del Cielo]] (Argentina), which had been obtained in 1783 by Miguel Rubín de Celis, discovering the presence in them of nickel (about 10%) along with iron.<ref>{{Cite book|title=Construyendo la Tabla Periódica|last=Calvo|first=Miguel|publisher=Prames|year=2019|isbn=978-84-8321-908-9|location=Zaragoza, Spain|pages=118}}</ref>