Stabilities of byströmite, MgSb₂O₆, ordoñezite, ZnSb₂O₆ and rosiaite, PbSb₂O₆, and their possible roles in limiting antimony mobility in the supergene zone

Abstract

Abstract In order to clarify the roles that secondary minerals may have in determining the extent of dispersion of Sb in the supergene environment, syntheses and stability studies of the Sb(V) oxides byströmite, MgSb 2 O 6 , ordoñezite, ZnSb 2 O 6 and rosiaite, PbSb 2 O 6 , have been undertaken. Solubilities in aqueous HNO3 were determined at 298.2 K and the data obtained used to calculate values of Δ at the same temperature. The derived Δ (s, 298.2 K) values for MgSb 2 O 6 (–1554.1 ±3.6 kJ mol –1 ), ZnSb 2 O 6 (–1257.0 ±2.6 kJ mol –1 ) and PbSb 2 O 6 (–1154.2 ±2.6 kJ mol –1 ) have been used in subsequent calculations to determine their relative stabilities and relationships with other secondary Sb minerals.