Xitieshanite

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

Xitieshanite
General
Category	Sulfate mineral
Formula	Fe3+(SO4)Cl·6(H2O)
IMA symbol	Xit[1]
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	[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]