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Wulfenite

Crystal System: Tetragonal
Status of Occurrence: Confirmed Occurrence
Distribution: Uncommon
Chemical Composition: Lead molybdate
Chemical Formula: PbMoO4
Method(s) of Verification: visual identification except:- Dylife Mine - XRD; East Glogfach Mine - XRD; Ty-Coch Mine - IR spectroscopy; Dolyhir Quarry - EMPA

Chemical Group:

Geological Context:

Introduction: wulfenite is a supergene lead mineral, typically encountered in the oxidation zones of veins, stockworks, disseminated and stratabound ore deposits in which galena and other primary lead minerals occur. The molybdenum may be supplied by molybdenum-bearing primary minerals such as molybdenite but in many cases, in which primary molybdenum is not present in sufficient quantity, it may be supplied by pervasive leaching of the wallrocks hosting the mineralisation. The classic associate of wulfenite is pyromorphite, but it may occur in association with a wide range of supergene minerals, particularly carbonates, phosphates and silicates. Wulfenite is an extremely stable mineral that tends to occur in fairly evolved supergene assemblages, characteristically in association with pyromorphite and cerussite as in the majority of its Central Wales occurrences (Mason, 2004). The associated species help with identification but the key is its distinctive crystal morphology and colour.
Occurrence in Wales: the first record of wulfenite in Wales, from Treffgarne Rocks in Pembrokeshire, was made as long ago as 1866, by Spencer George Percival. However, this was an erroneous identification - the mineral proving instead to be brookite - and it was not until just over 100 years had passed that the first authenticated occurrence, in Central Wales, was described (Ryback & Saville, 1967). Since that time, growing interest in the minerals of Wales has led to a minor flood of new occurrences: a review by Rothwell & Mason (1992) listed 22 Welsh localities and in the years since the list has grown to 29, including some important material in specimen terms. The majority of the localities (22 out of 29) are in the Central Wales Orefield.

Key Localities:

References:

  1. 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.
  2. Braithwaite, R.S.W., 1982b. Pyromorphite, wulfenite and other minerals from the Bwlch-Glas mine, Central Wales. Mineralogical Record, 13, 151-153.
  3. Braithwaite, R.S.W. & Lamb, R.P.H., 1986. Wulfenite from Ty Coch, Glamorgan (Powys), South Wales. Mineralogical Magazine, 50, 180-181.
  4. Cooper, M.P., 1987. New finds. British Micromount Society Newsletter, 20, 6-9.
  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., 1987. The minerals of Llechweddhelyg. U.K. Journal of Mines and Minerals, No. 3, 25-27.
  7. Jones, J.A. & Moreton, N.J.M., 1977. The Mines and Minerals of Mid-Wales 40pp.
  8. Mason, J.S., 2004. The development of supergene lead mineralisation in Central Wales. UK Journal of Mines and Minerals, 24, 35-46.
  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. Perceval, S.G., 1866a. Discovery of wulfenite, etc., in Pembrokeshire. Geological Magazine, 3, 377-378.
  11. Roe, D., 1988. New finds (Wulfenite from Mynydd Gorddu). British Micromount Newsletter, 22, 7.
  12. Rothwell, M. & Mason, J.S., 1992. Wulfenite in the British Isles. UK Journal of Mines & Minerals, 11, 30-41.
  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. Ryback, G. & Saville, G., 1967. Wulfenite from Ysbyty Ystwyth, Cardiganshire. Mineralogical Magazine, 36, 458-459.