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Cymraeg

Langite

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: many visual identifications, XRD data from: Cwmystwyth - (NHM, 3213F); Eaglebrook Mine - (NHM, 5843F); Frongoch Mine - (NHM, x10099, x10100 & 338F); Llechweddhelyg Mine - (NHM, 8032F & National Museum of Wales, NMW X-1123).

Chemical Group:

Geological Context:

Langite crystals (up to 1 mm in length) from Lodge Park copper trial, near Tre'r-ddol, in the Central Wales mining district. Specimen J.S. Mason Collection. Photo M.P. Cooper, © National Museum of Wales.
Blue-green, pseudohexagonal langite crystal from Darren Mine in the Central Wales Orefield. Specimen and photo S.A. Rust. © S.A. Rust.
Introduction: langite is a secondary mineral dimorphous with wroewolfeite and typically found within oxidized copper-bearing veinstone within mine dumps and underground as flowstone on mine walls. langite is frequently confused with wroewolfeite and posnjakite, other so-called langite-group minerals because of their similar blue-green colour. Well-crystallized specimens can be identified visually with relative confidence, but more often finely crystallized or amorphous-looking aggregates are encountered, which require additional analysis.
Occurrence in Wales: langite is the commonest of the so-called langite-group of minerals in Wales. The earliest account of langite from Wales is that by Jones & Moreton (1977) recording langite from a couple of sites in the Central Wales Orefield (Frongoch Mine and Esgair Fraith Mine). However, langite was confirmed from Frongoch during the 1960s by the Natural History Museum, London, on a sample collected by R.S.W. Braithwaite in 1962. Many more occurrences have come to light during the past twenty years, but the majority continue to be from the Central Wales Orefield and typically as microcrystals. The richest discovery to date was recorded by (Mason & Green, 1996) from the Lodge Park copper trial in north Ceredigion, where langite crystals coat adit walls.

Key Localities:

There are no key localities for this specimen.

References:

  1. Bevins, R.E. & Mason, J.S., 1998. Welsh Metallophyte and metallogenic evaluation project: Results of a Minesite Survey of Gwynedd. National Museums of Wales, Cardiff.
  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. 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.
  4. Jones, A.D., 1983. Nant-y-Cagl. Mineral Realm, 3, 42-76.
  5. Jones, J.A. & Moreton, N.J.M., 1977. The Mines and Minerals of Mid-Wales 40pp.
  6. Mason, J.S. & Green, D.I., 1996. Supergene copper mineralisation in situ at Lodge Park Copper trial, Dyfed. UK Journal of Mines and Minerals. 17. 19-23.
  7. 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.
  8. Rust, S., 1986. British Micro Localities. No. 15: Bwlchrennaid Mine or Level Newydd (SN 706 823), Goginan, Tirymynach, Wales. British Micromount Society Newsletter, 18, 9-10.
  9. Rust, S. & Rust, D., 1987. Micro-minerals from Dyfngwm Mine. U.K. Journal of Mines and Minerals, No. 2, 28-32.
  10. Rust, S., & Rust, D., 1986. British Micro Localities. No. 12 (continued): Dyfngwm Mine, Penegoes, Powys (SN 850931). British Micromount Society Newsletter. 16, 15-16.
  11. Rust, S.A., 1992. Ramsbeckite, the first three British occurrences. U.K. Journal of Mines and Minerals, No. 11, 24-25.
  12. 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.
  13. Rust, S.A. & Mason, J.S., 1988. The minerals of Esgair-Hir mine, Dyfed, Wales. UK Journal of Mines & Minerals, 5, 35-43.
  14. Saich, D.A. & Rust, S.A., 1987. Micro-minerals from a trial level in Wales. U.K. Journal of Mines and Minerals, No. 3, 3-4.

There are no references for this specimen.