DESCLOIZITE

vanadate mineral containing lead, copper, and zinc that usually forms brownish red to blackish brown crusts of intergrown crystals or rounded fibrous masses; its physical appearance is varied, however, and specimens have been found in shades from orange-red to black and various greens. The chemical formula for descloizite is (Zn,Cu)PbVO4(OH). Descloizite forms a solid-solution series with the similar mineral mottramite, in which copper replaces zinc in the crystal structure. These minerals occur with vanadinite in the oxidized zone of copper and lead deposits, as in the Otavi region, Namibia, where they are abundant; San Luis Potosi, Mex.; Baden, Ger.; and New Mexico. For detailed physical properties, see vanadate mineral (table).