Wroewolfeite

Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence
Distribution: Uncommon
Chemical Composition: Copper sulphate hydroxide hydrate
Chemical Formula: Cu4(SO4)(OH)6.2H2O
Method(s) of Verification: Darren Mine - XRD (NHM); Drws-y-Coed Mine - IR, (Braithwaite, 1982); Dylife Mine - visual; Eaglebrook Mine - Infrared spectroscopy (Braithwaite, 1982); Esgair Hir Mine - XRD (NHM); Frongoch Mine - XRD (NHM); Glasdir Mine - IR; Llechweddhelyg Mine - visual

Geological Context:

  • Supergene: post-mining oxidation & weathering deposits
Bladed wroewolfeite crystals up to 1 mm long, from Eaglebrook Mine. Specimen National Museum of Wales (NMW 87.43G.M.36), ex A. Dean Collection, © National Museum of Wales.
Introduction: wroewolfeite is a late stage supergene copper mineral typically formed as microcrystals in the oxidized zone of copper-bearing ore deposits and in post-mining dump environments.
Occurrence in Wales: described as a new species by Dunn & Rouse (1975) from the Loudville lead mine, Massachusetts, U.S.A., wroewolfeite was already known on specimens from Eaglebrook (Nantycagal) Mine in Cardiganshire (now Ceredigion). In 1965 R.S.W. Braithwaite collected some of the finest examples of the species from the dumps at Eaglebrook Mine, including well-formed bladed crystals up to 1 mm in length. Further investigations revealed wroewolfeite at Drws-y-Coed Mine, in North Wales and then during the 1980s and 1990s a small number of new occurrences at minesites in Central Wales came to light with the increasing popularity of micromineral collecting.

Key Localities:

  • Darren Mine, Pen-bont Rhydybeddau, Ceredigion: listed without description by Bevins (1994).
  • Drws-y-Coed Mine, Nantlle, Gwynedd: Braithwaite (1982) describes specimens collected by George Ryback in 1969. Wroewolfeite forms greenish-blue blades between 0.1 and 1 mm in length in association with amorphous blue-green crusts on calcite.
  • Dylife Mine, Penegoes, Powys: described by Rust & Rust (1987) as very rare thin to thick tabular greenish blue crystals tup to 1 mm in size.
  • Eaglebrook (Nantycagl) Mine, Ceulanymaesmawr, Ceredigion: this locality is well known as a source of finely crystallized specimens. Clear, sharp, greenish-blue blades exceeding 1 mm in length, with rectangular, chisel-shaped terminations are described by Braithwaite (1982). Braithwaite notes that the longer blades generally have less well defined terminations. Associated secondary minerals include linarite and brochantite, both of which pre-date the wroewolfeite.
  • Esgairhir Mine, Tal-y-bont, Ceredigion: a very rare component of the supergene assemblage. Rust & Mason (1988) recorded blue-green thin to thick tabular crystals, up to 0.8 mm in size, and prismatic crystals, typically encrusting or associated with altered chalcopyrite. Wroewolfeite has been observed in association with all of the other basic sulphate minerals and also, on rare occasions with cerussite.
  • Frongoch Mine, Devil's Bridge, Ceredigion: described by Green et al. (1996) as forming part of the mixed basic sulphate-covelline replacement of galena and cerussite, and rarely with hemimorphite as tabular crystals, up to 0.5 mm in size. Unusual, blocky deep blue-green microcrystals associated with minute gemmy cerussite crystals have been collected from underground workings (P. Hay pers. comm.).
  • Glasdir Mine, Dolgellau Gold-belt, Gwynedd: aggregates of blue microcrystals associated with malachite on shale are recorded by G. Ryback (Bevins, 1994).
  • Gwaith-yr-Afon Mine, Goginan, Ceredigion: Rust & Mason (1994) tentatively identified poorly-formed blue prismatic post-mining microcrystals of the langite group on chalcopyrite as wroewolfeite.
  • Llechweddhelyg Mine, Penrhyncoch, Ceredigion: very rare. Minute, dark blue-green euhedral chisel-shaped crystals occur within small cavities in pale altered veinstone.

There are no key localities for this specimen.

References:

  1. Bevins, R.E., 1994. A Mineralogy of Wales National Museum of Wales, Geological Series No. 16, Cardiff, 146pp.
  2. Bevins, R.E. & Mason, J.S., 1997. Welsh metallophyte and metallogenic evaluation project: Results of a minesite survey of Dyfed and Powys. CCW Contract Science Report No. 156. National Museums & Galleries of Wales.
  3. Braithwaite, R.S.W., 1982a. Wroewolfeite in Britain. Mineralogical Record, 13, 167-174.
  4. Dunn, P.J. & Rouse, R.C., 1975. Wroewolfeite, a new copper sulphate hydroxide hydrate. Mineralogical Magazine, 40, 1-5.
  5. 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.
  6. Jones, A.D., 1983. Nant-y-Cagl. Mineral Realm, 3, 42-76.
  7. Rust, S. & Rust, D., 1987. Micro-minerals from Dyfngwm Mine. U.K. Journal of Mines and Minerals, No. 2, 28-32.
  8. Rust, S.A. & Mason, J.S., 1994. An unusual occurrence of arsenate minerals at Gwaith-yr-Afon mine, Dyfed, Wales. Journal of the Russell Society, 5(2), 109-113.
  9. Rust, S.A. & Mason, J.S., 1988. The minerals of Esgair-Hir mine, Dyfed, Wales. UK Journal of Mines & Minerals, 5, 35-43.

There are no references for this specimen.