Hedleyite

Crystal System: Trigonal
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Distribution: Rare
Chemical Composition: Bismuth telluride
Chemical Formula: Bi7Te3
Method(s) of Verification: Clogau Mine - EMPA (Naden, 1988).

Chemical Group:

  • Sulphides

Geological Context:

  • Hydrothermal: mesothermal polymetallic veins
Introduction: hedleyite occurs typically with other tellurides in hydrothermal veins. It is also known from tellurium-enriched, skarn-type deposits.
Occurrence in Wales: only one occurrence - the first from the UK - has been noted, from Clogau Mine (Naden, 1988). No other examples have come to light despite quite extensive studies into the Clogau mineralization. Therefore, although confirmed analytically, the caution required with any ex-Kingsbury material due to his rather creative specimen provenancing practices (Ryback et al., 1998) has to be highlighted in this context.

Key Localities:

  • Bontddu, Dolgellau, Gwynedd: hedleyite occurs on a specimen (K3) in the Kingsbury Collection at the Natural History Museum, London, as tiny (20 µm) inclusions in galena (Naden, 1988).

References:

  1. Naden, J., 1988. Gold mineralisation in the Caledonides of the British Isles with reference to the Dolgellau Gold Belt and the Southern Uplands of Scotland. Unpublished Ph.D thesis, University of Aston, UK.
  2. Ryback, G., Clark, A.M. & Stanley, C.J., 1998. Re-examination of the A.W.G. Kingsbury Collection of British Minerals at the Natural History Museum, London. The Geological Curator, 6(9), 317-322.