Fine-grained galena is (or was) common at some of the Mid-Wales mines, where
the miners referred to it as "steel-ore". It long had a reputation of being
richly argentiferous with grades in the tens of ounces per ton.
In mineralogical terms this is a recrystallisation texture. Steel-ore
samples from the Darren and nearby mines have been examined in polished
section and the reason for their richly argentiferous nature is that they
contain lots of little inclusions of highly argentiferous tetrahedrite
(15-20 wt% Ag). Whilst I appreciate that you might not want to chip a bit
off your sample, it would nevertheless merit petrological investigation.
Tetrahedrite is certainly known from the Combe Martin mines.
Cheers - John
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