Wulfenite

Wulfenite is lead molybdate, PbMoO₄. It forms in the oxidation zones of lead deposits, where lead from weathered galena combines with molybdenum, and grows as square tablets: paper-thin plates or thick blocks, yellow, orange, red or honey brown. The mineral was first described from Bleiberg in Carinthia, Austria, and named in 1845 by Wilhelm Haidinger after Franz Xaver von Wulfen, the Jesuit naturalist who had studied the Bleiberg lead ores. Collectors know it from the Red Cloud and Glove mines in Arizona, Los Lamentos in Chihuahua, Mežica in Slovenia and Tsumeb in Namibia. Wulfenite is soft and brittle, and thin plates chip easily at their edges.