User:Anderson,Darrell/Chaidamuite

Chaidamuite
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 SO3                40.63 SiO2                 0.15 Al2O3               0.12 Fe2O3             20.00 FeO                  2.09 MnO                 0.06 ZnO                17.00 Na2O                 0.02 K2O                  0.01 H2O                19.21 Total               99.29   (1)

(1) Xitieshan mine, China; corresponds to (Zn0.85Fe2+ 0.12)_=0.97(Fe3+1.01Al0.01)_=1.02(SO4)2.05(OH)0.90 •3.87H2O.

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)O_5(OH)] and [Fe(2)O_5(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 (SO_4) tetrahedra sharing four pairs of octahedral corners on either side of the zigzag chains. These chains are cross-linked by the isolated [Zn(1)O_2(H_2O)_4] and [Zn(2)O_2(H_2O)_4] octahedra into corrugated sheets parallel to the (100) plane. Adjacent sheets are hydrogen bonded through water molecules (Li, et al 1990).

Physical Properties
Cleavage: On {001} and {100}, perfect. Fracture: conchoidal. Hardness: = 2.5–3 D(meas.) = 2.722(2) D(calc.) = 2.72 Optical Properties: Translucent. Color: Brown to yellow-brown. Streak: Pale yellow. Luster: Vitreous. Optical Class: Biaxial (+). Pleochroism: Strong; X = pale yellow to colorless; Y = pale yellow; Z = brownish yellow. Orientation: X = b; Y ^ a = 12_; Z ^ c = 28_. Dispersion: r < v, strong. _ = 1.632(1) _ = 1.640(1) = 1.688(1) 2V(meas.) = 44(2)_  (Li, et al, 1990).