Pyromorphite is a mineral belonging to the phosphate group. Its chemical formula is Pb₅(PO₄)₃Cl, meaning it is a lead phosphate containing chlorine. Pyromorphite typically forms in the oxidation zones of lead ore deposits, where primary lead minerals such as galena undergo alteration.
The pyromorphite specimens presented below illustrate this diversity of forms, colors, localities and mineral associations.
Pyromorphite crystallizes in the hexagonal crystal system, which means its internal structure is organized around sixfold symmetry. In collections, this may result in prismatic crystals, but it is also common to observe compact aggregates or surfaces covered with closely intergrown small crystals.
Crystal habits observed in collections
Pyromorphite can display several crystal habits (the external shape of the crystals):
• Prismatic crystals: elongated forms, sometimes showing a hexagonal cross-section.
• Acicular aggregates: groups of fine needle-like crystals.
• Botryoidal forms: rounded surfaces resembling a cluster of grapes.
• Druses: small crystals coating a rock matrix.
Color and visual appearance
Pyromorphite is most commonly green, sometimes in vivid tones, but it may also occur in yellow, orange, brown or light grey shades. These variations reflect local chemical conditions within the deposit.
Its luster is generally resinous to slightly bright, and well-formed crystals may be translucent.
Associated minerals
In lead deposits, pyromorphite may occur alongside cerussite, anglesite, galena, vanadinite or wulfenite, depending on the local geochemical environment.
Physical properties
• Hardness: 3.5 to 4 on the Mohs scale (a relatively soft mineral that should be handled with care).
• Density: high (around 7), due to its lead content.
Collecting interest and localities
Pyromorphite is appreciated by collectors for the diversity of its crystal habits and its range of colors. At Le Monde Minéral, the pyromorphite specimens offered originate mainly from French deposits and, depending on availability, from Hunan, China, allowing comparison of different habits and appearances within the same mineral species.
