Xitieshanite

Xitieshanite is a hydrous iron sulfate–chloride mineral with chemical formula: Fe3+(SO4)Cl·6(H2O).

Xitieshanite
General
CategorySulfate mineral
Formula
(repeating unit)		Fe3+(SO4)Cl·6(H2O)
IMA symbolXit[1]
Strunz classification7.DC.20
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/a
Unit cella = 14.1 Å, b = 6.9 Å
c = 10.67 Å; β = 111.26°; Z = 4
Identification
Formula mass313.47 g/mol
ColorGreen; yellow green
Crystal habitAcicular
CleavageUncertain / indistinct
FractureConchoidal to uneven
Mohs scale hardness2.5 - 3
LusterVitreous
StreakYellow
DiaphaneityTransparent to translucent
Specific gravity1.99
Optical propertiesBiaxial (-)
Refractive indexnα = 1.536 nβ = 1.570 nγ = 1.628
Birefringence0.092
PleochroismColorless (x) to pale yellow (y) to light greenish yellow (z)
2V angleMeasured: 77°
Dispersionr > v
References[2][3]

It was discovered in 1983 and named for the discovery location of Xitieshan lead/zinc ore deposit in the Qinghai Province, China. It was approved by the IMA in the year of its discovery.[4] The mineral has also been reported in 2005 from acid mine drainage from a coal mine in Green Valley, Vigo County, Indiana.[5]

Properties

Xitieshanite mainly consists of oxygen (56.14%) and iron (17.82%), but otherwise contains chlorine (11.31%), sulphur (10.23%) and hydrogen (4.50%). This mineral grown in lead-zinc mines, in the oxidation zone of it. Xitieshanite is a pleochroic mineral, which is an optical phenomenon, meaning the mineral appears as if it's changing colors depending on the axis it is being inspected at. On the X axis it appears as it's colorless, while it looks pale yellow if viewed on the Y axis, and light greenish yellow on the Z axis. It doesn't show any radioactive properties whatsoever.[4]

References
  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. Xitieshanite mineral data from Webmineral
  3. Mindat.org
  4. "Xitieshanite Mineral Data". www.webmineral.com. Retrieved 2022-03-10.
  5. Melchiorre, Erik, et al., A new occurrence of xitieshanite [Fe3+(SO4)Cl·6H2O] crystals in acid-mine seepways, Green Valley, Vigo County, Indiana, U.S.A., American Mineralogist, v. 90 no. 10 p. 1518-1521, 2005


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