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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!!).
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