Chaidamuite

Chaidamuite is a rare zinc – iron sulfate mineral with chemical formula: ZnFe³⁺(SO₄)₂(OH)·4H₂O.

Chaidamuite
General
Category	Sulfate minerals
Formula	ZnFe3+(SO4)2(OH)·4(H2O)
IMA symbol	Cdm[1]
Strunz classification	7.DC.30
Crystal system	Triclinic
Crystal class	Pedial (1) (same H-M symbol)
Space group	P1
Unit cell	a = 7.309(2) Å, b = 7.202(2) Å, c = 9.691(3) Å; α = 89.64(3)°, β = 105.89(1)°, γ = 91.11(1)°; Z = 2
Identification
Color	Brown to yellow-brown
Crystal habit	Tabular pseudocubic crystals and granular masses; pseudomonoclinic
Cleavage	On {001} and {100}, perfect.
Fracture	conchoidal
Mohs scale hardness	2.5–3
Luster	Vitreous
Streak	Pale yellow
Diaphaneity	Translucent
Optical properties	Biaxial (+)
Refractive index	nα = 1.632 nβ = 1.640 nγ = 1.688
Birefringence	δ = 0.056
Pleochroism	Strong: X= pale yellow, colorless; Y= pale yellow; z= Brownish yellow
2V angle	44°
References	[2][3][4][5]

It was first described for an occurrence in the Xitieshan mine south of Mt. Qilianshan in the Chaidamu basin, Qinghai Province, China and was named for the locality. It occurs as an oxidation phase in a lead zinc deposit. In the type locality it is associated with the rare minerals: coquimbite, copiapite, butlerite and zincobotryogen.^[5] In addition to the Chinese occurrence, it has been reported from the Getchell Mine in the Potosi District in Humboldt County, Nevada.^[3]