Green mawbyite, PbFe3+F0.42+Zn0.6(AsO4)(2)OH(H2O), from the Lagoa mine, northern Portugal

摘要

An occurrence of an unusual, green-coloured mawbyite was found coating arsenopyrite in a specimen from the Lagoa mine, Northern Portugal. Electron microprobe analyses combined with a single-crystal structure refinement gives the formula as PbFe3+F0.42+Zn0.6(AsO4)(2)OH(H2O). The change of color from the usual bright red or orange color of maw-byite is attributed to the high concentration of divalent cations, Fe2+ and Zn, in the metal atom site.