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Cymraeg

Anglesite

Crystal System: Orthorhombic
Status of Occurrence: Confirmed Occurrence - Type Locality In Wales
Distribution: Locally Abundant
Chemical Composition: Lead sulphate
Chemical Formula: PbSO4
Method(s) of Verification: Parys Mountain - XRD at the Natural History Museum, London; Central Wales Orefield - many localities by XRD including Cwmystwyth, Dylife, Eaglebrook, Esgairhir & Frongoch (all at the NHM, London); Dolyhir Quarry - XRD (Manchester Museum).

Chemical Group:

Geological Context:

Rich yellow anglesite crystals in gossan from Mona Mine, Parys Mountain, Anglesey. Crystals reach up to 10 mm in length. National Museum of Wales specimen (NMW 86.83G.M.1). Photo M.P. Cooper, © National Museum of Wales.
Pale yellow to colourless anglesite crystals (up to 4 mm in length) from Mona Mine, Parys Mountain, Anglesey. National Museum of Wales specimen (NMW 91.12G.M.5), ex Barstow, ex Sutcliffe collections. Photo M.P. Cooper, © National Museum of Wales
Colourless prismatic anglesite crystal 1.2 mm tall from a cavity in oxidized galena-tennantite from Dolyhir Quarry. N. Hubbard Collection. Photo D.I. Green. © D.I. Green.
Introduction: anglesite occurs in the oxidation zones of lead-bearing ore deposits. It forms early during the galena alteration process, in relatively acidic conditions where fluid circulation is restricted. In more open systems, carbonate ions contributed by dissolved CO2 in rainwater raise the pH beyond that where anglesite is stable and the much commoner lead carbonate, cerussite, forms instead. Similar micro-environments occur within mine spoil and anglesite is not uncommon as a post-mining mineral, often in association with covellite and linarite. The name anglesite is derived from Anglesey, the island in North Wales upon which the mineral was first discovered - at Parys Mountain.
Occurrence in Wales: Although named by Beudant (1832), the existence of this mineral, previously known as 'vitriol de plomb', at Parys Mountain had been known for many years. It was, for example, mentioned by Monnet (1779). The late 18th Century was the time when the majority of the anglesite specimens from Parys Mountain were obtained, for example specimen 91.6G.M.1 in the National Museum of Wales Collection, which was collected in 1784. These specimens were discovered during removal of the gossan overlying the primary sulphide zone and few have been found since: consequently well-formed Parys Mountain anglesites now command high prices on the mineral specimen market. Other minor occurrences of anglesite in North Wales are from Bwlch Mine, near Deganwy (Russell, 1944), Castell Carn Dochan Mine, near Bala (S.A. Rust Collection) and from Llanengan (XRD record, Natural History Museum, London) and Penrhyn-Du mines on the Llŷn. More recently, anglesite has been identified at a significant number of old lead mines and also at several working quarries across Wales with a nucleus of occurrences, many of the post-mining category, within the Central Wales Orefield. Apart from the more noteworthy occurrences described in detail under 'key localities' below, it has been reported from Bodcoll Mine (Bevins & Mason, 1997), Bwlchrhennaid Mine (British Micromount Society Newsletter 18), Cwmystwyth Mine (Natural History Museum, London, XRD record), Darren Mine (Rust, 1990), Esgairddu Mine (Bevins & Mason, 1997), Esgairmwyn Mine (S.A. Rust Collection), Gellireirin Mine (Bevins & Mason, 1997), Geufron Mine (British Micromount Society Newsletter 15), Glogfawr Mine (British Micromount Society Newsletter 16), Hafan Mine (S.A. Rust Collection), Hendrefelin Mine (S.A. Rust Collection), Henfwlch Mine (T.F. Cotterell, unpublished data), Llettyevan-hen Mine (S.A. Rust Collection), Mynyddgorddu Mine (D.I. Green, unpublished data), South Nantycar Mine (British Micromount Society Newsletter 34), Nantycreiau Mine (T.F. Cotterell, unpublished data), Penpompren Mine (S.A. Rust Collection), Penrhiw Mine (Mason & Green, 1995), Quarry Shaft, Llywernog Mine (S.A. Rust Collection) and Ystrad Einion Mine (Mason & Rust, 1997). In South Wales, some very fine specimens of anglesite were obtained at Machen Quarry in the 1980s (see below) and it has also been recorded from Rhyd-y-Gwern Mine, near Machen (Natural History Museum, London, XRD record) and from Hendy Quarry, Miskin (British Micromount Society Newsletter 35).

Key Localities:

There are no key localities for this specimen.

References:

  1. Beudant, F.S., 1832. Traité élémentaire de Minéralogie. 2nd Edition. Paris.
  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., 1982b. Pyromorphite, wulfenite and other minerals from the Bwlch-Glas mine, Central Wales. Mineralogical Record, 13, 151-153.
  4. Braithwaite, R.S.W., 1982a. Wroewolfeite in Britain. Mineralogical Record, 13, 167-174.
  5. Green, D.I., 1995. Carbonate-cyanotrichite from the Wedding Cave mine, Bwlchgwyn, Clwyd. UK Journal of Mines & Minerals, 15, 19.
  6. 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.
  7. Jones, A.D., 1987. The minerals of Llechweddhelyg. U.K. Journal of Mines and Minerals, No. 3, 25-27.
  8. 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.
  9. 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.
  10. Monnet, M., 1779. Nouveau Systême de Minéralogie. Paris.
  11. Russell, A., 1944. Notes on some minerals either new or rare in Britain. Mineralogical Magazine, 27, 1-10.
  12. Rust, S. & Rust, D., 1987. Micro-minerals from Dyfngwm Mine. U.K. Journal of Mines and Minerals, No. 2, 28-32.
  13. Rust, S.A., 1990a. Mattheddleite from the Darren Mine, Dyfed, Wales. UK Journal of Mines and Minerals. 8, 47-48.
  14. 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.