{{Short description|Iron carbide mineral}} {{Infobox mineral | name = Cohenite | category = Native element mineral, carbide | boxwidth = | boxbgcolor = | image = Kristallstruktur Zementit.png | imagesize = | caption = Structure of cohenite (or cementite) | formula = (Fe,Ni,Co)<sub>3</sub>C | IMAsymbol=Coh<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | strunz = 1.BA.05 | system = Orthorhombic | class = Dipyramidal (mmm) <br/>H-M symbol: (2/m 2/m 2/m) | symmetry = ''Pnma'' | unit cell = a = 5.09 Å, b = 6.74 Å, <br/>c = 4.52 Å; Z = 4 | color = Tin-white; oxidizes to light bronze then golden yellow | habit = Platy to needlelike crystals; also as rims on or in dendritic intergrowths with iron | twinning = | cleavage = Good on {100}, {010}, and {001} | fracture = | tenacity = Brittle | mohs = 5.5–6 | luster = Metallic | polish = | refractive = | opticalprop = | birefringence = | dispersion = | pleochroism = | fluorescence= | absorption = | streak = | gravity = 7.2–7.65 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Opaque | other = Strongly magnetic | references = <ref>[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Cementit Mineralienatlas]</ref><ref name=Mindat>[http://www.mindat.org/min-1107.html Mindat.org Cohenite]</ref><ref name=Webmin>[http://www.webmineral.com/data/Cohenite.shtml Webmineral.com Cohenite]</ref><ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/cohenite.pdf Handbook of Mineralogy]</ref> }}
'''Cohenite''' is a naturally occurring iron carbide mineral with the chemical structure (Fe, Ni, Co)<sub>3</sub>C. This forms a hard, shiny, silver mineral which was named by E. Weinschenk in 1889 after the German mineralogist Emil Cohen, who first described and analysed material from the Magura meteorite found near Slanica, Žilina Region, Slovakia.<ref name=Mindat/> Cohenite is found in rod-like crystals in iron meteorites.<ref>Vagn F. Buchwald, ''Handbook of Iron Meteorites,'' University of California Press, 1975 {{ISBN|978-0520029347}}</ref>
On Earth cohenite is stable only in rocks which formed in a strongly reducing environment and contain native iron deposits. Such conditions existed in some places where molten magmas invaded coal deposits, e.g. on Disko Island in Greenland, or at the Bühl near Kassel in Germany.<ref name=HBM/>
Associated minerals include native iron, schreibersite, troilite and wüstite.<ref name=HBM/>
Similar iron carbides occur also in technical iron alloys and are called cementite.
==See also== *Edscottite * Glossary of meteoritics *List of minerals *List of minerals named after people
== References == {{Reflist}}
{{Meteorites}}
Category:Carbide minerals Category:Iron minerals Category:Meteorite minerals Category:Orthorhombic minerals Category:Minerals in space group 62 Category:Native element minerals