Pyromorphite, which is a member of the apatite group, is a Lead Chlorophosphate mineral that forms close series with mimetite. Distinguishing between the two can be difficult, especially when the crystals are similar colors. It is used as a mineral ore of lead, and is usually found in association with other lead-bearing minerals such as cerussite and galena, as well as limonite. Significant localities include mines in Idaho and Pennsylvania, USA, as well as at Mapimi in Mexico, along with others in Germany, England, and Australia. Pyromorphite forms barrel-shaped crystals that have hexagonal sections — these are usually green, but can also be yellow, orange, or brown. It has a specific gravity of ~7.0+, a resinous to adamantine luster, and an off-white streak.