Schulenbergite

Crystal System: Trigonal
Status of Occurrence: Confirmed Occurrence
Distribution: Uncommon
Chemical Composition: Copper zinc sulphate carbonate hydroxide hydrate
Chemical Formula: (Cu,Zn)7(SO4,CO3)2(OH)10.3H2O
Method(s) of Verification: all Central Wales occurrences have been confirmed by X-ray diffraction. Eaglebrook Mine - XRD (NHM, 6879F); Dylife Mine (listed as Dyfngwm Mine, but shown to be part of Dylife) - XRD (NHM, 7029F); Brynarian Mine - XRD (NHM, x20225); Copa Hill - XRD

Chemical Group:

  • Sulphates

Geological Context:

  • Supergene: post-mining oxidation & weathering deposits
Schulenbergite (turquoise) aggregates (up to 0.5 mm across) associated with linarite (blue) from Penrhiw Mine. J.S. Mason Collection (JMPR515). © National Museum of Wales.
Scanning electron micrograph of an aggregate of twisted schulenbergite plates with minor pseudohexagonal susannite (bright white) from Frongoch Mine. National Museum of Wales Collection (NMW 2003.1G.M.229). © National Museum of Wales.
Introduction: schulenbergite is a rare secondary species typically developed through post-mining oxidation of copper- and zinc-bearing veinstone within mine dumps.
Occurrence in Wales: described as a new species by Hodenberg et al. in 1984, the rare secondary mineral schulenbergite was first noted in Wales by Rust (1992). Subsequent analyses of samples collected from a number of other localities in Central Wales have shown this region to be unusually 'rich' in schulenbergite occurrences. All of these occurrences are post-mining in origin, schulenbergite being formed through the interaction of groundwater with copper- and zinc-rich veinstone in mine dumps or through mine waters reacting with similar waste rock used as backfill within old mine workings.

Key Localities:

  • Brynyrarian Mine, Tre-Taliesin, Ceredigion: noted associated with very rare ramsbeckite (Rust, 1992).
  • Copa Hill, Cwmystwyth mines, Ceredigion: noted as confirmed from Copa Hill by the Natural History Museum, London (Bevins, 1994).
  • Dylife Mine, Penegoes, Powys: forms pearly turquoise blue-green crusts coating weathered sphalerite derived from dumps on the outcrop of Pen Dylife Lode close to Dylife Shaft.
  • Eaglebrook (Nantycagl) Mine, Ceulanymaesmawr, Ceredigion: bright blue-green, slightly twisted hexagonal crystals in rosettes covering areas to 4 mm are reported in the British Micromount Society Newsletter (No. 22).
  • Frongoch Mine, Devil's Bridge, Ceredigion: occurs as light blue-green rosettes of thin platy crystals to 0.7 mm, and as drusy crusts within weathered veinstone (Green et al., 1996).
  • Henfwlch Mine, Ceulanymaesmawr, Ceredigion: occurs as an uncommon mineral at this locality. Schulenbergite forms bright turquoise blue-green to pale blue aggregates of confused, twisted crystals intimately associated with serpierite within low-grade sulphide ore used as backfill underground (T.F. Cotterell, unpublished data).
  • Llangynog Mine, Llangynog, Powys: crystal groups, up to 2 mm across, occur on a specimen in the S.A. Rust Collection.
  • Penrhiw Mine, Ystumtuen, Ceredigion: relatively common as extensive pale blue poorly-crystalline coatings on the external surfaces of siltstone-dolomite blocks. Crystals, typically pseudohexagonal in form are often intergrown into rosettes. Crystals reach 1.5 mm but, are more usually 0.5 to 1 mm in size (Mason & Green, 1995). Specimens from Penrhiw are the richest from Wales in terms of coverage.
  • Ystrad Einion Mine, Furnace, Ceredigion: crusts of near-white hexagonal platy crystals (up to 0.75 mm) associated with minor serpierite are known from underground workings (Mason & Rust, 1997).

References:

  1. Bevins, R.E., 1994. A Mineralogy of Wales National Museum of Wales, Geological Series No. 16, Cardiff, 146pp.
  2. 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.
  3. Hodenberg, R. von, Krause, W. & Tauber, H., 1984. Schulenbergite, (Cu,Zn)7(SO4,CO3)2(OH)10.3H2O a new mineral. Neues Jahrbuch fur Mineralogie Monatschefte, 17-24.
  4. 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.
  5. 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.
  6. Rust, S.A., 1992. Ramsbeckite, the first three British occurrences. U.K. Journal of Mines and Minerals, No. 11, 24-25.