Matildite

Crystal System: Hexagonal
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Distribution: Rare
Chemical Composition: Silver bismuth sulphide
Chemical Formula: AgBiS2
Method(s) of Verification: Clogau Mine - electron microprobe (Naden (1988).

Chemical Group:

  • Sulphosalts

Geological Context:

  • Hydrothermal: mesothermal polymetallic veins
Introduction: matildite is found, with other bismuth minerals, in medium-temperature ore deposits.
Occurrence in Wales: only one occurrence, limited to a single microscopic grain, of matildite has been noted in Wales.

Key Localities:

  • Clogau Mine, Bontddu, Gwynedd: Naden (1988) recorded a single microscopic (40 ┬Ám) grain of matildite occurring within a complex assemblage with tellurobismuthite, tetradymite, galena, chalcopyrite, pyrrhotite, hessite, altaite, gold, ''wehrlite', cobaltite and native bismuth. The sample was obtained from the No. 4 Level below the main Llechfraith Adit.

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 Unpublished Ph.D thesis, University of Aston, UK.