Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Chemical Composition: Basic hydrated copper zinc sulphate
Chemical Formula: (Cu,Zn)15(SO4)4(OH)12·6H2O
Method(s) of Verification: Penrhiw Mine - XRD (National Museum of Wales, NMW X-795); Brynyrarian Mine - XRD (NHM, London); Dylife Mine - XRD (NHM, London).
- Supergene: post-mining oxidation & weathering deposits
Introduction: ramsbeckite occurs in mine tips where sulphide-rich spoil has undergone weathering, and is also known from weathered metalliferous slags. It is invariably associated with other rare Cu-Zn bearing supergene species such as schulenbergite, namuwite and serpierite. The association most frequently occurs within voids in corroded vein carbonates adjacent to part-weathered sulphides. The visual identification of ramsbeckite is assisted by its crystal morphology (diamond-shaped crystals) and colour (a distinctive, lustrous bottle-green).
Occurrence in Wales: only first described as a mineral in 1987, ramsbeckite is one of a considerable number of microcrystalline supergene minerals restricted in their occurrence to the post-mining mineralization environment. The first UK occurrences of ramsbeckite date from the period 1985-1990 (Rust, 1992); however the finds at Penrhiw Mine between 1992 and 1995 set a new standard for the species (Mason & Green, 1995). Since then further minor UK occurrences have been discovered, most of which have been in Central Wales.
- Brynyrarian Mine, Tre-Taliesin, Ceredigion: rare poorly-crystallized masses and scattered microcrystals (Rust, 1992).
- Dylife Mine, Penegoes, Powys: bright green pseudo-orthorhombic crystals and elongate rod-like prisms (Rust, 1992).
- Eaglebrook (Nantycagl) Mine, Ceulanymaesmawr, Ceredigion: emerald green crystals (up to 0.5 mm) associated with linarite and hemimorphite (S.A. Rust collection).
- Frongoch Mine, Devil's Bridge, Ceredigion: emerald-green pseudo-orthorhombic crystals up to 0.7 mm (Green et al., 1996).
- Llangynog Mine, Llangynog, Powys: crystals up to 0.5 mm in size (S.A. Rust collection).
- Penrhiw Mine, Ystumtuen, Ceredigion: extensive crystalline crusts with crystals up to 3 mm in size, associated with well-crystallized schulenbergite, which it post-dates. It occurs both on weathered sulphide-rich veinstone and within voids in weathered dolomitic carbonate veinlets in mudstone, the latter producing the best specimens (Mason & Green, 1995).
- Ystrad Einion Mine, Furnace, Ceredigion: minute emerald-green blocky crystals on schulenbergite; extremely rare (Mason & Rust, 1997).
- Green, D.I., Rust, S.A. & Mason, J.S., 1996. Classic British mineral localities: Frongoch Mine, Dyfed. UK Journal of Mines & Minerals, 17, 29-38.
- Mason, J.S. & Green, D.I., 1995. Supergene minerals including exceptional ramsbeckite from Penrhiw Mine, Ystumtuen, Dyfed. UK Journal of Mines & Minerals, 15, 21-27.
- Mason, J.S. & Rust, S.A., 1997. The Mineralogy of Ystrad Einion Mine, Dyfed, Wales. U.K. Journal of Mines and Minerals, 18, 33-36.
- Rust, S.A., 1992. Ramsbeckite, the first three British occurrences. U.K. Journal of Mines and Minerals, No. 11, 24-25.