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Nagyagite

Crystal System: Orthorhombic
Status of Occurrence: Discredited Occurrence
Distribution: See individual species entries for details
Chemical Composition: Lead gold tellurium antimony sulphide
Chemical Formula: Pb5Au(Te,Sb)4S5-8
Method(s) of Verification:

Chemical Group:

  • Sulphides

Geological Context:

  • Hydrothermal: mesothermal polymetallic veins
  • Hydrothermal: epithermal polymetallic veins & pipes
Introduction: nagyagite typically occurs in precious metal deposits, including both mesothermal and epithermal gold-lodes. It is typically accompanied by other gold and silver tellurides.
Occurrence in Wales: the presence of 'nagyagite' was noted by Gilbey (1968), who described it occurring as thin contact-rims between native gold and tellurides in a sample from Clogau Mine, Bontddu, Gwynedd. However, subsequent work with the electron microprobe on this sample, by D.H.M. Alderton, indicated that the rim-forming phase was in fact native bismuth, a re-identification published by Mason et al. (2002). Therefore, nagyagite is not a valid Welsh species.

Key Localities:

There are no key localities for this specimen.

References:

  1. Gilbey, J.W., 1968. The mineralogy, paragenesis and structure of the ores of the Dolgellau Gold Belt, Merionethshire, and associated wall rock alteration. Unpublished Ph.D thesis, University of London, UK.
  2. Mason, J.S., Bevins, R.E. & Alderton, D.H.M., 2002. Ore Mineralogy of the mesothermal gold lodes of the Dolgellau Gold Belt, North Wales. Transactions of the Institution of Mining and Metallurgy (Section B, Applied earth science), 111, B203-B214.