Solubility of the nadorite group minerals : implications for mobility of Sb and Bi in oxidised settings

As part of a study of the control that secondary minerals exert on the dispersion of antimony and bismuth in the supergene environment, syntheses and stability studies of nadorite (PbSbO2Cl) and perite (PbBiO2Cl) have been undertaken. Solubilities in aqueous HNO3 were determined at 298.2 K and the data obtained used to calculate values of ΔGfθ(298.2 K). The ΔGfθ(s, 298.2 K) values for PbSbO2Cl (–622.0 ± 2.8 kJ mol–1) and PbBiO2Cl (–590.0 ± 1.3kJ mol–1) have been used in subsequent calculations to determine relative stabilities and relationships with other common secondary Sb and Bi minerals. While the role of nadorite in immobilising Sb is dependent upon the prevailing redox potential such that SbIII is stable, perite may be a significant phase in limiting the dispersion of Bi in certain supergene settings.