Mimetite and Pyromorphite Rare Mineral - New Mexico 2.4 oz are both lead-bearing minerals in the apatite group that are chemically and structurally similar, often making them difficult to distinguish without testing. Mimetite is a lead arsenate, while pyromorphite is a lead phosphate. They are found in similar hexagonal crystalline forms, typically in shades of yellow, orange, brown, and green, and form a continuous solid-solution series where arsenic and phosphorus can substitute for each other. Mimetite Chemical Formula: \(Pb_{5}(AsO_{4})_{3}Cl\)Resembles: Pyromorphite and vanadiniteColors: Typically yellow, orange-yellow, orange, or brown; rarely green or colorlessCrystal System: HexagonalLuster: Resinous or sub-adamantineHardness: 3.5-4 on the Mohs scaleOther: Named "mimetite" from the Greek word for "imitator" because it so closely resembles pyromorphite Pyromorphite Chemical Formula: Resembles: Mimetite and vanadiniteColors: Often green, but can also be yellow, yellow-orange, orange-brown, and shades of brown or grayCrystal System: HexagonalLuster: ResinousHardness: 3.5-4 on the Mohs scaleOther: Formerly known as "green lead ore" (Grünbleierz) Key differences and similarities Chemical makeup: The primary difference is the element in the anion group: mimetite has arsenate (\(AsO_{4}\)), while pyromorphite has phosphate (\(PO_{4}\)).Crystal structure and form: Both minerals have a similar hexagonal crystal structure and are often found in barrel-shaped crystals or rounded masses.Color: While colors overlap, pyromorphite is more commonly green, whereas mimetite is more often in the yellow to orange range.Solid-solution series: In nature, they form a solid-solution series where phosphorus and arsenic can substitute for each other, meaning many specimens are mixtures rather than pure samples. Pyromorphite - WikipediaPyromorphite is a mineral species composed of lead chlorophosphate: 488