Zincian carbonates from the oxidized zone of the Waryński mine, Upper Silesia, Poland, a Pb‐Zn ore deposit, were analyzed by aem techniques. Compositions lie in the system CaCO3‐MgCO3‐(Fe,Mn)CO3‐ZnCO3, within three one-phase areas of CaCO3‐rich, dolomite, and CaCO3‐poor solid solutions similar to those in the system CaCO3-MgCO3‐FeCO3, (Rosenberg, 1967). Dolomite solid solutions extend from CaMg(CO3)2, to at least 72 mol% CaZn(CO3)2, and have electron‐diffraction patterns consistent with the R3 dolomite structure. The extent of solid solution is greater toward CaZn(CO3)2, than toward CaFe(CO3)2, in the system CaCO3‐MgCO3-FeCO3, at higher temperatures. However, neither of these end‐members has been observed in nature or synthesized. CaCO3‐poor solid solutions approach the system FeCO3‐ZnCO3, whereas CaCO3‐rich solid solutions are close in composition to the CaCO3 end‐member.

Analyses of carbonates from the Waryriski mine and from Tsumeb, Namibia (Garavelli etal., 1982), as well as inferences from experimental studies (Goldsmith, 1983) suggest that the dolomite end‐member CaZn(CO3)2 may be stable at low temperatures.

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