What is Pyromorphite?
Pyromorphite is a dense lead phosphate with vivid green barrel-shaped crystals, one of the most desirable display minerals from oxidised lead deposits.
Mineralogy and crystal structure
Reference formula: Pb5(PO4)3Cl. Pyromorphite is a hexagonal member of the apatite group and forms a solid-solution series with mimetite and vanadinite. Lead content requires responsible handling. Pyromorphite is classified with phosphates and has a hexagonal crystal system. Typical hardness is 3.5–4 on the Mohs scale and specific gravity is approximately 6.5–7.1.
Colour, lustre and habit
Typical colours include bright green, yellow, brown, orange, grey. The usual prismatic, barrel-shaped, botryoidal habit and resinous, vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Pyromorphite forms in or is associated with oxidised zones of lead veins where phosphate-bearing groundwater alters galena. Important documented localities include China, Namibia, Mexico, Germany, France, Australia and the United States.
Green barrels from a weathered lead vein
Pyromorphite is a collector favourite because the crystals are both graphic and scientifically legible: oxidation transforms a lead sulfide vein into bright phosphate forms.
Collecting and care
Keep enclosed, avoid dust and acids, and do not grind or use lead-bearing specimens for jewellery or food-contact objects.
