Beudantite

Crystal System: Trigonal
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Lead iron arsenate sulphate hydroxide
Chemical Formula: PbFe3(AsO4)(SO4)(OH)6
Method(s) of Verification: all published records of beudantite from Wales have been verified. Darren Mine - XRD at the National Museum of Wales (NMW X-942); Dolyhir Quarry - EMPA (Manchester Museum); Ystrad Einion Mine - XRD (Natural History Museum).

Chemical Group:

  • Arsenates

Geological Context:

  • Supergene: in situ natural oxidation & weathering deposits
Scanning electron micrograph of an individual beudantite crystal from Dolyhir Quarry. Photo D.I. Green, © D.I. Green.
Introduction: a secondary mineral typically formed in the oxidized zone of lead-bearing ore bodies and within weathered lead-rich mine spoil.
Occurrence in Wales: records of beudantite in Wales are few. Bevins (1994) briefly mentioned an identification of beudantite from Ystrad Einion Mine near Tre'r-ddol, in the Central Wales Orefield. This, the first Welsh occurrence was described in detail by Mason & Rust (1997). Further investigations looking into the identification of secondary minerals in Central Wales has, revealed the presence of beudantite at Darren Mine. However, the absence of any substantial primary arsenic phases within the Central Wales Orefield clearly limits the possibility of further significant finds. In the Welsh Borderland, beudantite has recently been recorded in the oxidized portions of a tennantite-dominated vein in Wenlock Limestone at Dolyhir Quarry.

Key Localities:

  • Darren Mine, Pen-bont Rhydybeddau, Ceredigion: beudantite is rare at this locality (Bevins & Mason, 1997). National Museum of Wales specimens (collected by J.S. Mason) show glistening green-brown crusts of minute globular beudantite aggregates, associated with yellow, powdery beaverite and minor cerussite.
  • Dolyhir Quarry, Old Radnor, Powys: beudantite forms a very rare component of an oxidized section of the main sulphide vein, exposed in 1995/1996. One minute crystalline specimen showing euhedral, yellow crystals to about 0.2 mm was collected from the main vein and yellow crusts on sulphide fragments from clay fault gouge at the top of the vein contain beudantite (D.I. Green, unpublished data).
  • Ystrad Einion Mine, Furnace, Ceredigion: very rare, minute (< 0.15 mm) transparent yellow-green rhombohedral crystals forming sparkling crusts on goethite in thin joints in veinstone (Mason & Rust, 1997). Rarely associated with beaverite.

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. 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.

There are no references for this specimen.