Piromorfita
Piromorfita is a mineral with formula Pb₅(PO₄)₃Cl, in the Fosfatos group. This specimen comes from Yanga Koubenza Quarries, Mfouati, Mfouati District, Bouenza Department, República del Congo and joined the Terrium collection in 2026.
Description
Trident. Three pyromorphite crystals, the largest c. 2.5 cm. Small cluster, but with an unusually large main crystal. Strong resinous lustre and apple-green colour.
History of this specimen
The piece is restored. It arrived perfect, but when taking it out it slipped. In barely a month and a half my right thumb has failed me three times. It is twisting outwards. Age does not forgive. It forms a set with mimetite 0299 and vanadinite 0298.
About Piromorfita
One of the three lead chloroapatites. Lead chlorophosphate, isomorphous with vanadinite (V) chlorovanadate and mimetite (As) chloroarsenate. All belong to the chloroapatite group, which crystallise as hexagonal prisms.
About the locality
Yanga–Koubenza produces very irregular, episodic mineralisation. The mine prioritises tonnage and specimen recovery is difficult, so many pieces are damaged or not preserved. Here pyromorphite usually occurs as a solitary species, with well-formed prismatic crystals, slightly curved faces, and colours from apple green to darker green. Typical crystals are 5 to 15 mm. Specimens with clearly larger crystals or with very elongated growths are rare and, when they occur, they often arrive damaged. This specimen lies outside the norm, with a main crystal reaching almost 3 cm, an uncommon size for the locality and one of those exceptional cases within the known production.
Technical data
- Catalogue No.
- 0300
- Composition
- Pb₅(PO₄)₃Cl
- Name
- Piromorfita
- Group
- Fosfatos
- Category
- Estélites
- Mine
- Yanga Koubenza Quarries
- District / Municipality
- Mfouati
- Province
- Mfouati District
- Region
- Bouenza Department
- Country
- República del Congo
- Size (cm)
- 3 x 2.6 x 1
- Weight
- 10 g
- Acquired
- 2026
- Etymology
- From the Greek "pyro" (fire) and "morphé" (form), for changing colour on heating.
- Quality
- Notable
- Value trend
- Al alza