Hi Dave,
The Harlech Dome manganese mines worked carbonate-silicate manganese ores,
which formed a statiform bed best developed around the southern/western
flanks of the Rhinogau, chiefly from above Bontddu, around west to Barmouth
and northwards beyond Harlech.
Although the footwall-rocks have a bit of cubic pyrite, it never
constituted a signifcant component of the mineralisation.
Chief pyrite localities where it was recovered for "sulphur" ie. sulphuric
acid & byproducts were:
Cae Coch near Llanwrst - a huuuu-uuuge massive volcanogenic pyrite deposit,
now chiefly famous for the extraordinary acid-water loving microbiology
that thrives underground - the so-called acid streamers that some of us
trolls refer to as "snot-gobblies". David Jenkins of Bangor did the
groundbreaking work on this site. Estimated to be 100 cubic M of biomass in
there living off the oxidising pyrite!!
Brynyrafr and Cwmrheidol/Ystumtuen mines - as noted by Bernard - in Central
Wales both produced "pyrites" which was marcasite. Production nothing close
to Cae Coch but the mineralisation can still be classified as significant.
In environmental terms it still is!!!
Parys Mountain: I don't know whether this site produced pyrite or not but
there is one hell of a lot of it there!
That's it so far as I can immediately recall. Cae Coch was the mega-site.
Dave - give me the locality names and I'll try to look into it in more
detail for you.
All the best - John
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