J.S. Mason - Central Wales Orefield: Early and late varieties of galena

Galena impregnating fine-grained turbidite sandstone wallrock from Leri Valley mine, Talybont (L). The effect only goes in a few mm from the vein margin. This texture is quite rare in Central Wales, and appears to be limited to the early, complex polymetallic mineralisation.

Later mineralising events have generally started with the deposition of a thin (just visible in this case!) layer of quartz on wallrock clasts (R), thus forming a barrier to subsequent fluids. In general, ore petrologists will find later Central Wales galenas relatively disappointing - hardly any inclusions or much else of note (as a very general rule!!).