keilite
{{Short description|Iron-magnesium sulfide mineral}}
{{Infobox mineral
| name = Keilite
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| category = Sulfides
| formula = {{chem2|(Fe(2+),Mg)S}}
| molweight = 81.91 gm
| strunz = 2/C.15-15
| dana = 2.8.1.9
| system = Isometric
| class = Hexoctahedral
| symmetry = Fm{{overline|3}}m (No. 225)
| unit cell = a = 5.1717(18)Å
| color =
| colour = Grey
| habit = Microscopic crystals
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| cleavage = Distinct/good
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| tenacity = Brittle
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| luster = Metallic
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| diaphaneity = Opaque
| gravity = 3.958
| density = 3.958
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Keilite is an iron-magnesium sulfide mineral with the chemical formula {{chem2|(Fe,Mg)S)}} that is found in enstatite chondrites.{{Cite web|last=|first=|date=|title=Keilite Mineral Data|url=http://webmineral.com/data/Keilite.shtml|archive-url=|archive-date=|access-date=15 February 2021|website=WebMineral}} Keilite is the iron-dominant analog of niningerite.{{Cite web|last=|first=|date=|title=Keilite|url=http://www.handbookofmineralogy.com/pdfs/Keilite.pdf|url-status=dead|archive-url=https://web.archive.org/web/20160303171359/http://www.handbookofmineralogy.com/pdfs/keilite.pdf|archive-date=3 March 2016|access-date=15 February 2021|website=Handbook of Mineralogy}}{{Cite journal|vauthors=Shimizu M, Yoshida H, Mandarino JA|title=The New Mineral Species Keilite, (Fe,Mg)S, The Iron-Dominant Analogue of Niningerite|url=https://rruff.info/doclib/cm/vol40/CM40_1687.pdf|journal=The Canadian Mineralogist|year=2002|volume=40|issue=6|pages=1687–1692|doi=10.2113/gscanmin.40.6.1687|bibcode=2002CaMin..40.1687S |s2cid=93381076 |via=}} Keilite is named after Klaus Keil (born 1934).
Occurrences
Examples of keilite occurrences are enstatite chondrites and the Zakłodzie meteorite. It appears to be confined to impact-melt influenced enstatite chondrites that were quenched. There are also some meteorites interpreted as impact-melt breccias that do not contain keilite. This is explained as a deeper burial after impact, which slowed cooling and enabled retrograde reactions (diapthoresis) to take place.{{cite journal|last=Keil|first=Klaus|title=Occurrence and origin of keilite, (Fe>0.5,Mg<0.5)S, in enstatite chondrite impact-melt rocks and impact-melt breccias|journal=Chemie der Erde - Geochemistry|date=30 April 2007|volume=67|issue=1|pages=37–54|doi=10.1016/j.chemer.2006.05.002|bibcode=2007ChEG...67...37K}}