{{Short description|Sulfate mineral}} {{infobox mineral | name = Siderotil | image = | imagesize = | alt = | caption = | category = Sulfate minerals | formula = Fe<sup>2+</sup>SO<sub>4</sub>·5H<sub>2</sub>O | IMAsymbol = Sdt<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> | molweight = | strunz = 7.CB.20 | dana = | system = Triclinic | class = Pinacoidal ({{overline|1}}) <br/><small>(same H-M symbol)</small> | symmetry = ''P''{{overline|1}} | unit cell = a = 6.26&nbsp;Å, b = 10.63&nbsp;Å <br/>c = 6.06&nbsp;Å; α = 97.25° <br/>β = 109.67°, γ = 75°; Z&nbsp;=&nbsp;2 | color = Pale green, yellowish, white | colour = | habit = Fibrous to powdery, rarely as acicular crystals | twinning = | cleavage = | fracture = | tenacity = | mohs = 2.5 | luster = Vitreous or silky | streak = | diaphaneity = Transparent to translucent | gravity = 2.1 - 2.2 | density = | polish = | opticalprop = Biaxial (-) | refractive = n<sub>α</sub> = 1.513 - 1.515 n<sub>β</sub> = 1.525 - 1.526 n<sub>γ</sub> = 1.534 - 1.536 | birefringence = δ = 0.021 | pleochroism = | 2V = Measured: 50°, calculated: 80° to 86° | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = Soluble in water | impurities = | alteration = | other = | references = <ref name=Mindat/><ref name=HBM/><ref name=Webmin>[http://www.webmineral.com/data/Siderotil.shtml Webmineral data]</ref> }} '''Siderotil''' is an iron(II) sulfate hydrate mineral with formula: FeSO<sub>4</sub>·5H<sub>2</sub>O which forms by the dehydration of melanterite.<ref name=Mindat>[http://www.mindat.org/min-3643.html Mindat.org]</ref> Copper commonly occurs substituting for iron in the structure. It typically occurs as fibrous or powdery encrustations, but may also occur as acicular triclinic crystals.<ref name=HBM/>

It was first described in 1891 for an occurrence in the Idrija Mine, Idrija, Slovenia. Its name derives from the Greek ''sideros'' (iron) and ''tilos'' (fiber) in reference to its iron content and typical fibrous form.<ref name=Mindat/> However, the material at the Idrija location may not be siderotil, but the mineral has been authenticated from a wide variety of worldwide locations.<ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/siderotil.pdf Handbook of Mineralogy]</ref>

==References== {{Reflist}}

Category:Sulfate minerals Category:Iron(II) minerals Category:Triclinic minerals Category:Minerals in space group 2 Category:Chalcanthite group

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