Siderotil

Siderotil is an iron(II) sulfate hydrate mineral with formula: FeSO4·5H2O which forms by the dehydration of melanterite.[1] 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.[2]

Siderotil
General
CategorySulfate minerals
Formula
(repeating unit)
Fe2+SO4·5H2O
Strunz classification7.CB.20
Crystal systemTriclinic
Crystal classPinacoidal (1)
(same H-M symbol)
Space groupP1
Unit cella = 6.26 Å, b = 10.63 Å
c = 6.06 Å; α = 97.25°
β = 109.67°, γ = 75°; Z = 2
Identification
ColorPale green, yellowish, white
Crystal habitFibrous to powdery, rarely as acicular crystals
Mohs scale hardness2.5
LusterVitreous or silky
DiaphaneityTransparent to translucent
Specific gravity2.1 - 2.2
Optical propertiesBiaxial (-)
Refractive indexnα = 1.513 - 1.515 nβ = 1.525 - 1.526 nγ = 1.534 - 1.536
Birefringenceδ = 0.021
2V angleMeasured: 50°, calculated: 80° to 86°
SolubilitySoluble in water
References[1][2][3]

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.[1] However, the material at the Idrija location may not be siderotil, but the mineral has been authenticated from a wide variety of worldwide locations.[2]

References


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