Editing Siderite (section)

{{Short description|Mineral composed of iron(II) carbonate}}
{{For|the type of meteorite|Iron meteorite}}
{{Infobox mineral
| name        = Siderite
| category    = [[Carbonate mineral]]
| boxwidth    = 
| boxbgcolor  = 
| image       = Harvard Museum of Natural History. Siderite. Gilman, Eagle Co., CO (DerHexer) 2012-07-20.jpg
| imagesize   = 260px
| alt         = 
| caption     = 
| formula     = FeCO<sub>3</sub>
| IMAsymbol   = Sd<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      = 5.AB.05
| dana        = 14.01.01.03
| system      = [[Trigonal]]
| class       = Hexagonal scalenohedral ({{overline|3}}m) <br/>[[H-M symbol]]: ({{overline|3}} 2/m)
| symmetry    = ''R''{{overline|3}}c
| unit cell   = ''a'' = 4.6916 <br> ''c'' = 15.3796&nbsp;[Å]; ''Z''&nbsp;=&nbsp;6
| color       = Pale yellow to tan, grey, brown, green, red, black and sometimes nearly colorless
| habit       = Tabular crystals, often curved; botryoidal to massive
| twinning    = Lamellar uncommon on{01{{overline|1}}2}
| cleavage    = Perfect on {01{{overline|1}}1}
| fracture    = Uneven to conchoidal
| tenacity    = Brittle
| mohs        = 3.75–4.25
| luster      = Vitreous, may be silky to pearly
| streak      = White
| diaphaneity = Translucent to subtranslucent
| gravity     = 3.96
| density     = 
| polish      = 
| opticalprop = Uniaxial (−)
| refractive  = ''n''<sub>ω</sub> = 1.875 <br> ''n''<sub>ε</sub> = 1.633
| birefringence = ''δ'' = 0.242
| pleochroism = 
| 2V          = 
| dispersion  = Strong
| extinction  = 
| length fast/slow =
| fluorescence= 
| absorption  =
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = 
| other       = 
| alteration  = 
| references  = <ref name="handbook">{{cite book |title=Handbook of Mineralogy: Borates, Carbonates, Sulfates |year=2003 |publisher=Mineral Data Publishing |location=Tucson, Arizona |isbn=9780962209741 |url=https://rruff.info/doclib/hom/siderite.pdf |access-date=2022-11-30 |archive-url=https://web.archive.org/web/20220313194153/https://rruff.info/doclib/hom/siderite.pdf |archive-date=13 March 2022 |language=en |chapter=Siderite}}</ref><ref name="Mindat">{{Mindat |id=3647 |name=Siderite |access-date=2022-11-30}}</ref><ref name="Webmin">{{WebMineral |url=https://webmineral.com/data/Siderite.shtml |name=Siderite Mineral Data |access-date=2022-11-30}}</ref>
}}

'''Siderite''' is a [[mineral]] composed of [[iron(II) carbonate]] (FeCO<sub>3</sub>). Its name comes from the [[Ancient Greek]] word {{wikt-lang|grc|σίδηρος}} ({{grc-transl|σίδηρος}}), meaning "iron". A valuable [[iron ore]], it consists of 48% [[iron]] and lacks [[sulfur]] and [[phosphorus]]. [[Zinc]], [[magnesium]], and [[manganese]] commonly substitute for the iron, resulting in the siderite-[[smithsonite]], siderite-[[magnesite]], and siderite-[[rhodochrosite]] [[solid solution]] series.<ref name=Mindat/>

Siderite has [[Mohs scale of mineral hardness|Mohs hardness]] of 3.75 to 4.25, a [[specific gravity]] of 3.96, a white [[Streak (mineralogy)|streak]] and a [[vitreous lustre|vitreous]] or [[Lustre (mineralogy)#Pearly lustre|pearly luster]]. Siderite is [[Antiferromagnetism|antiferromagnetic]] below its [[Néel temperature]] of {{cvt|37|K|C|0}} that can assist in its identification.<ref>{{cite journal |last1=Frederichs |first1=T. |last2=von Dobeneck |first2=T. |last3=Bleil |first3=U. |last4=Dekkers |first4=M. J. |title=Towards the identification of siderite, rhodochrosite, and vivianite in sediments by their low-temperature magnetic properties |journal=Physics and Chemistry of the Earth, Parts A/B/C |date=January 2003 |volume=28 |issue=16–19 |pages=669–679 |doi=10.1016/S1474-7065(03)00121-9|bibcode=2003PCE....28..669F }}</ref>

It crystallizes in the [[trigonal crystal system]]; crystals are [[rhombohedral]] in shape, typically with curved and striated faces. It also occurs in masses. Color ranges from yellow to dark brown or black, the latter being due to the presence of manganese.

Siderite is commonly found in [[Hydrothermal circulation|hydrothermal]] [[Vein (geology)|veins]], and is associated with [[barite]], [[fluorite]], [[galena]], and others. It is also a common [[Diagenesis|diagenetic]] mineral in [[shale]]s and [[sandstone]]s, where it sometimes forms [[concretion]]s, which can encase three-dimensionally preserved [[fossils]].<ref>{{cite journal |first1=Russell |last1=Garwood |first2=Jason A. |last2=Dunlop |first3=Mark D. |last3=Sutton |year=2009 |title=High-fidelity X-ray micro-tomography reconstruction of siderite-hosted Carboniferous arachnids |journal=[[Biology Letters]] |volume=5 |issue=6 |pages=841–844 |doi=10.1098/rsbl.2009.0464 |pmid=19656861 |pmc=2828000}}</ref> In [[sedimentary rock]]s, siderite commonly forms at shallow burial depths and its elemental composition is often related to the [[Sedimentary depositional environment|depositional environment]] of the enclosing sediments.<ref>{{cite journal|last=Mozley |first=P. S. |date=1989 |title=Relation between depositional environment and the elemental composition of early diagenetic siderite |journal=Geology |volume=17 |issue=8 |pages=704–706|doi=10.1130/0091-7613(1989)017<0704:RBDEAT>2.3.CO;2 }}</ref> In addition, a number of recent studies have used the [[Oxygen isotopes|oxygen isotopic composition]] of sphaerosiderite (a type associated with [[soil]]s) as a [[Proxy (climate)|proxy]] for the [[Isotope|isotopic]] composition of [[meteoric water]] shortly after deposition.<ref>{{cite journal|last1=Ludvigson |first1=G. A. |last2=Gonzalez |first2=L. A. |last3=Metzger |first3=R. A. |last4=Witzke |first4=B. J. |last5=Brenner |first5=R. L. |last6=Murillo |first6=A. P. |last7=White |first7=T. S. |date=1998 |title=Meteoric sphaerosiderite lines and their use for paleohydrology and paleoclimatology |journal=Geology |volume=26 |issue=11 |pages=1039–1042|doi=10.1130/0091-7613(1998)026<1039:MSLATU>2.3.CO;2 }}</ref> Evidence of the presence of siderite on Mars is being interpreted as a possible indicator of the presence of abundant water early in the climate history of that planet.<ref>Janice Bishop and M. Lane, ''Catching a glimpse of ancient Mars'', [[Science]], Vol. 388, April 18, 2025, p. 251. doi: 10.1126/science.adw4889 </ref><ref>Benjamin Tutolo et al., ''Carbonates identified by the Curiosity rover indicate a carbon cycle operated on ancient Mars'', Science, Vol. 388, April 18, 2025, p. 292. doi: 10.1126/science.ado9966 </ref><ref>Grossman, Lisa, ''[https://www.sciencenews.org/article/nasa-curiosity-rover-mars-missing-carbon A NASA rover finally found Mars’ missing carbon: The finding could help explain why Mars lost its habitable climate]'', [[Science News]], April 17, 2025 </ref>