pyromorphite

Pyromorphite crystals, Chihuahua, Mexico.

pyromorphite, a phosphate mineral, lead chloride phosphate, [Pb₅(PO₄)₃Cl], that is a minor ore of lead. It occurs with galena, cerussite, and limonite in the oxidized zone of lead deposits, where it forms very brightly coloured, heavy, barrel-shaped crystals or globular masses. For properties, see phosphate mineral (table).

Arsenic and vanadium often replace phosphorus in the pyromorphite structure. Thus, in nature, pyromorphite occurs mixed with both mimetite and vanadinite; these mixtures, called solid-solution series, show continuous chemical variation between the pure compounds. Pyromorphite is a member of a group of minerals related to apatite in structure and properties.