Pt-Ag-Au alloy

Crystal System: Cubic
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Gold-silver-platinum alloy
Chemical Formula: Au2AgPt0.04
Method(s) of Verification: Afon Wen - EMPA (National Museum of Wales).

Chemical Group:

  • Elements & Alloys

Geological Context:

  • Hydrothermal: mesothermal polymetallic veins
  • Sedimentary
Introduction: alloys of gold and silver with minor to moderate levels of platinoids occur locally in various hypogene gold deposits and in placers. However, as a general comment the platinoid metals are rare in most gold deposits and the converse is also the case in that gold tends to be only a very minor component of classic platinoid deposits (Boyle, 1979).
Occurrence in Wales: despite various claims relating to occurrences of native platinum and other PGM's in the Dolgellau Gold-belt, dating back to the 19th Century (e.g. Readwin, 1888), no subsequent discoveries have been made, as noted in the sections of this site concerning those native elements. However the presence of small amounts of this platinum-bearing alloy in a single grain of alluvial gold from the area was determined analytically in 2001 during research studies at the National Museum of Wales.

Key Localities:

  • Afon Wen, Gwynedd: during an electron microprobe examination of a polished section of five flakes of alluvial gold from the placer deposits of this river, a thin (0.1 mm) wide veinlet of clearly different composition was detected in one grain by using the equipment in backscatter mode. Analysis of the veinlet showed it to be a silver-rich gold alloy (Afon Wen gold tends to be >> 90% Au 10% Ag) carrying nearly 1.5% Pt (National Museum of Wales/ J.S. Mason, unpublished data).


  1. Boyle, R.W., 1979. The Geochemistry of Gold and its Deposits. Bulletin of the Geological Survey of Canada, 280.
  2. Readwin, T.A., 1888. Gold in Wales. London, 12pp.