Mineral Database
Corkite
Crystal System: Trigonal
Formula: PbFe3+3(PO)4(SO)4(OH)6
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Lead iron phosphate sulphate hydroxide
Method(s) of Verification: Frongoch Mine - XRD & semi-quantitative EDS (National Museum of Wales, X-ray number NMW X-1401).
Scanning electron micrograph of rhombic corkite crystals on goethite from Frongoch Mine. National Museum of Wales Collection (NMW 2005.10G.M.1). © National Museum of Wales.
Chemical Group:
- Phosphates
- Sulphates
Geological Context:
- Supergene : post-mining oxidation & weathering deposits
- Supergene : in situ natural oxidation & weathering deposits
Introduction: corkite is a rare secondary species typically found within phosphate-dominated secondary mineral assemblages, particularly associated with lead-rich orebodies.
Occurrence in Wales: corkite has only recently been discovered in Wales (Cotterell and Todhunter, 2007) forming, minute euhedral crystals in iron stained quartz veinstone from Frongoch mine, in the Central Wales Orefield. Only a very small number of specimens are known, but this reflects the inconspicuous nature of this species.
Key Localities:
- Frongoch Mine, Devil's Bridge, Ceredigion: identified on specimens collected from the extensive dumps as minute (<0.3 mm) yellowish-green to olive-green rhombic crystals on goethite-coated quartz (Cotterell and Todhunter, 2007).
References:
- Corkite and hinsdalite from Frongoch mine, Devil's Bridge, Ceredigion, Wales, including evidence to suggest that orpheite is a variety of hinsdalite. Journal of the Russell Society, 10, 57-64.
