Mineral formation from aqueous solution. Part I. The deposition of hydrozincite,Zn5(OH)6(CO3)2, from natural waters

Summary Naturally occurring waters in the oxidized zone of a Pb-Zn orebody have been collected where they are responsible for the formation of solid hydrozincite, Zn₅(OH)₆(CO₃)₂. The solutions were analysed and the computer programme COMICS used to describe the complex ion distribution in each case. From the results, the solubility product for hydrozincite has been recalculated as log K_SP=–14.9(0.1). This value has been used to calculate the fields of stability of some secondary zinc minerals and illustrates the reason for the apparently anomalous stability of hydrozincite in nature, compared with what might be expected from considerations of earlier data.