Plynlimon Mine, Ponterwyd, Cwmrheidol, Ceredigion, Wales, UKi

Regional Level Types
Plynlimon Mine	Mine (Abandoned)
Ponterwyd	- not defined -
Cwmrheidol	- not defined -
Ceredigion	County
Wales	Country
UK	Country

Probably the highest mine developed in the mid-Wales area at 540 mts. Although the mine is one of the most remote in in mid-Wales. It was quite succesfull at times. A shoot of ore was developed between the 36 and 48 fathom levels for a lenth of about 58 fathoms. The first recorded working was in about 1854, and then on a number of occassions utill 1896.
The total recorded output is 3271 tons of lead ore.

Jan 2019. The mine was developed on a lode that obliquely crosses the stream from the south-west to north-east. An adit is located above the track on the west bank whilst between the track and stream are several spoil heaps and a well preserved wheelpit.
Tips dominate the eastern bank with 2 shafts and a flooded open gunnis towards the north where the track crosses the stream. The tips have been excavated for aggregate for the track which is consequently a source of galena.
There is a prominent dam that once retained a reservoir north of the bridge. Where the dam has been breached the stone facing on the pond side has been revealed. The course of the aqueduct from the western side of the dam is apparent and beneath the tips beside the stream the remnants of a wooden boxed launder can be seen.
A further shaft is located at the crest of the hill on the north east side of the site, though development does not appear to have been extensive.
The main tips are abundant with solid pieces of galena many bigger than a golf ball with bright cubic crystal habit (possibly the best samples of galena from any of the mines so far visited within the Ceredigion Mountains locality). Sphalerite and marcasite are also relatively common, whilst pyromorphite is uncommon though abundant within individual samples. The tip at the north-eastern shaft on the hilltop produces abundant calcite associated with pyrite, rarely as 1-2mm cubes, and is also abundant with sphalerite whilst galena is noteably absent which represents a distinct change from the main tips which were presumably excavated from the shafts beside the stream.
Also notable is the tip associated with the adit which is barren for minerals but is comprised of highly fractured sandstone, whereas the main tip is comprised of blocks of foliated mudstone and the tip at the crest of the hill is of a paler mudstone. These are all classed within the Bryn-glas formation but clearly represent different phases of deposition as noted by the British Geological Survey: "Bryn-glas Formation - Slumped Mudstone, Slumped Siltstone And Slumped Sandstone. Sedimentary Bedrock formed approximately 444 to 445 million years ago in the Ordovician Period. Local environment previously dominated by deep seas. These sedimentary rocks are marine in origin. They are detrital and comprise coarse- to fine-grained slurries of debris from the continental shelf flowing into a deep-sea environment, forming distinctively graded beds."

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