Beaverite

Crystal System: Trigonal
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Lead copper iron aluminium sulphate hydroxide
Chemical Formula: Pb(Cu,Fe,Al)3(SO4)2(OH)6
Method(s) of Verification: Darren Mine - XRD at the National Museum of Wales; Ystrad Einion Mine - XRD at the Natural History Museum, London.

Chemical Group:

  • Sulphates

Geological Context:

  • Supergene: post-mining oxidation & weathering deposits
  • Supergene: in situ natural oxidation & weathering deposits
Introduction: beaverite is a supergene mineral typically occurring in the oxidized zones of lead-copper bearing ore deposits, or in post-mining assemblages at lead/copper mines. In many of its worldwide localities it is found with Fe-bearing arsenates such as beudantite and carminite. It is not particularly easy to identify, because of its rather indistinctive appearance (powdery yellow-brown crusts being fairly typical).
Occurrence in Wales: beaverite is, due to its colour and habit, easily overlooked by mineralogists and may be more widespread in Wales than the two Central Wales records would suggest. These both resulted from XRD analyses of specimens collected by micromineral specialists during the 1990s.

Key Localities:

  • Darren Mine, Pen-bont Rhydybeddau, Ceredigion: powdery yellowish crusts associated with iron oxides and beudantite have been identified as beaverite (National Museum of Wales specimens).
  • Ystrad Einion Mine, Furnace, Ceredigion: beaverite is relatively common as a component of a post-mining supergene assemblage found in a local occurrence underground at this mine (Mason & Rust, 1997). It forms yellow-brown microbotryoidal crusts and rarer spherical masses of platy microcrystals up to 1 mm in size. It is associated with goethite and beudantite but is often overgrown by basic copper and zinc sulphates.

References:

  1. 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.