Clogau-St David's lode. Clogau Mine, Wales, Britain

The Dolgellau gold belt of north Wales contains gold mineralization within shear zones and veins in the Clogau shales and Vigra flags of Middle to Upper Cambrian age. In the Clogau-St David's lode the mineralization is enclosed in a quartz and carbonate gangue. Gold is associated with arsenopyrite and pyrite and with bismuth-tellurium mineralization.

Major Minerals:

Arsenopyrite, pyrite, marcasite

Minor Minerals:

Pyrrhotite, chalcopyrite, sphalerite, galena, cobaltite, tellurobismutite, native gold, magnetite

Trace Minerals:

Include tetradymite, hessite, altaite, native bismuth, tetrahedrite, bismuthinite, pyrargyrite, bournonite, graphite, TiO2 minerals


Pyrrhotite is altered to pyrite and marcasite. Replacement of pyrite by native gold is common, forming symplectite-like intergrowths. Galena forms discontinuous rims between tellurobismutite and tetradymite


Bottrell et al., 1988