Crystal System: Trigonal
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Distribution: Rare
Chemical Composition: Bismuth telluride
Chemical Formula: Bi4Te3
Method(s) of Verification: Clogau Mine - 'wehrlite' revealed by EMPA (Naden, 1988).

Chemical Group:

  • Sulphides

Geological Context:

  • Hydrothermal: mesothermal polymetallic veins
Introduction: pilsenite occurs in complex bismuth telluride assemblages typically associated with gold deposits.
Occurrence in Wales: the presence of 'wehrlite' was recorded in galena dominated gold-bearing veins at Clogau Mine by Naden (1988). However it has been shown that 'wehrlite' is not a valid mineral species but is instead intimately intergrown pilsenite and hessite (Ozawa & Shimazaki, 1982). Thus, by default, pilsenite found its way onto the Welsh mineral species list.

Key Localities:

  • Clogau Mine, Bontddu, Gwynedd: intergrowths of pilsenite with hessite occur as grains which were identified by Naden (1988) as the subsequently discredited species wehrlite.


  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 Unpublished Ph.D thesis, University of Aston, UK.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. Ozawa, T. & Shimazaki, H., 1982. Pilsenite redefined and wehrlite discredited. Proceedings of the Japanese Academy, 58, 291.