The extent to which secondary Sb minerals control Sb dispersion in the supergene environment is yet to be fully understood. Stability studies of klebelsbergite have been undertaken to better under-stand its role in controlling Sb mobility and relationships with other secondary Sb minerals. Solubility in aqueous 0.1084 M HNO3 was determined at 298.15 K and the data obtained used to derive Gfθ(klebelsbergite, s, 298.15 K) =-2056.4 ± 5.0 kJ/mol. Solubility data have been used to deduce the conditions under which the mineral can form as a thermodynamically stable phase. The single-crystal X-ray structure of synthetic klebelsbergite has been determined 293 K and is essentially the same as that reported earlier for atoms with Z ≥ 8. Crystal data: orthorhombic, space group Pca21, a = 5.7563(4), b = 11.2538(7), c = 14.8627(9) Å, V = 962.81(11) Å3, Z = 4. Refinement converged to R1 = 0.0154 for 2206 unique reflections with I > 2σ(I). The present study has located the hydroxyl H atoms on both O5 and O9. The H-bond arrangements are somewhat different to those proposed earlier with the quasi-linear O9-H···O3 interaction having <(DHA) = 171(6)°. The O5 hydroxyl H atom lies in a different position to that proposed earlier and is involved in a bifurcated H-bond arrangement with O2 and with itself in a symmetry-related position, with <(DHA) = 133(5) and 125(5)°, respectively.
- antimony sulfate
- hydrogen bonding