Xitieshanite

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

Xitieshanite
General
Category	Sulfate mineral
Formula (repeating unit)	Fe3+(SO4)Cl·6(H2O)
IMA symbol	Xit
Strunz classification	7.DC.20
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/a
Unit cell	a = 14.1 Å, b = 6.9 Å c = 10.67 Å; β = 111.26°; Z = 4
Identification
Formula mass	313.47 g/mol
Color	Green; yellow green
Crystal habit	Acicular
Cleavage	Uncertain / indistinct
Fracture	Conchoidal to uneven
Mohs scale hardness	2.5 - 3
Luster	Vitreous
Streak	Yellow
Diaphaneity	Transparent to translucent
Specific gravity	1.99
Optical properties	Biaxial (-)
Refractive index	nα = 1.536 nβ = 1.570 nγ = 1.628
Birefringence	0.092
Pleochroism	Colorless (x) to pale yellow (y) to light greenish yellow (z)
2V angle	Measured: 77°
Dispersion	r > v
References

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. The mineral has also been reported in 2005 from acid mine drainage from a coal mine in Green Valley, Vigo County, Indiana.

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.