Many single specimens of the rare Fe mineral siderotil in a capsule. From Runge Mine, Edgemont, Fall River County, South Dakota, United States of America. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Siderotil
Iron sulfate pentahydrate — what melanterite becomes as it dehydrates.
Intro adapted from Wikipedia (CC BY-SA).
Siderotil is an IMA-recognized mineral species in the sulfate class, with the chemical formula Fe(SO₄)·5H₂O.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Chalcanthite structural group.
Key properties: Mohs hardness 2.5; specific gravity 2.1–2.2; White streak; Vitreous luster; refractive index 1.525; optically biaxial.
IMA symbol Sdt, IMA status: approved, named in 1892.
Forms by dehydration of cuprian melanterite.
It is found associated with Melanterite.
Its name comes from the Greek for iron, sideros, and for fiber, tilos, in reference to its composition and structure.