Chaidamuite

Chaidamuite
General
Category	Sulfate minerals
Chemical formula	ZnFe3+(SO4)2(OH)·4(H2O)
Strunz classification	07.DC.30
Crystal symmetry	Triclinic pedial 1 - pseudomonoclinic
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 system	Triclinic
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	[1][2][3][4]

Chaidamuite is a sulfate mineral that was first found in Xitieshan mine south of Mt. Qilianshan in the Chaidamu basin, Qinghai (Chinghai) Province, China. It is named from locality and is a hydrated sulfate containing a hydroxyl and four dihydrogen monoxide molecules. It a secondary mineral possibly formed due to mining process.

Composition

Chemistry: ZnFe³⁺(SO₄)₂(OH)·4H₂O

Structure

The crystal structure has been determined by the Patterson method and Fourier syntheses and refined by the full-matrix least-squares method to an R factor of 0.032, using 2833 independent reflections. In the structure, a zigzag chain consists of [Fe(1)O₅(OH)] and [Fe(2)O₅(OH)] octahedra sharing the OH corners, and an octahedral-tetrahedral chain running parallel to the b axis consists of the zigzag chain of Fe octahedra and (SO₄) tetrahedra sharing four pairs of octahedral corners on either side of the zigzag chains. These chains are cross-linked by the isolated [Zn(1)O₂(H₂O)₄] and [Zn(2)O₂(H₂O)₄] octahedra into corrugated sheets parallel to the (100) plane. Adjacent sheets are hydrogen bonded through water molecules (Li, et al 1990).

References

1. ^ Li, W.M., and Wang, Q.G. (1990) Determination and Refinement of the Crystal Structure of Chaidamuite (Issue 5). Science in China Series B-Chemistry, 33, 623-630
2. ^ Mindat.org
3. ^ Webmineral data
4. ^ Handbook of Mineralogy

Bibliography

• Clark, A.M. (1993) Hey’s Mineral Index (3rd edition). Alphabetical Index of Mineral Species, Varieties and Synonyms and Chemical Classification. 121 p. Chapman & Hall, New York, NY.
• Jambor, J.L., and Burke, E.A.J. (1990) New Mineral Names. American Mineralogist, 75, 1431-1437.
• Li, W., Chen, G., and Peng, Z. (1986) Chaidamuite. Acta Mineralogica Sinica, 6, 109.
• Li, W.M., and Wang, Q.G. (1990) Determination and Refinement of the Crystal Structure of Chaidamuite (Issue 5). Science in China Series B-Chemistry, 33, 623-630
• Mandarino, J.A., and de Fourestier, J., (2005) Mineral Species First Found in People’s Republic of China. (No. 2). Rocks and Minerals, 80, 114-117.