Gwydyr Lead Mines
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The Gwydyr Forest has been the scene of lead and zinc mining since the 17th Century. The myriad of small, ancient workings developed with the coming of the railway to the Conwy Valley in the 19th Century into larger, better organised concerns. Often share speculation in the hands of unscrupulous dealers & promoters was more important than actually removing ore from the ground. A few mines such as Parc and Aberllyn were viable and they continued to produce ore well into this century. For the most part however, most of the mines are small, overgrown and forgotten. They heyday of the mines was during the second half of the 19th Century when a combined total of about 25,000 tonnes of lead and zinc ore were extracted, mainly from the mines in the vicinity of Llyn Sarnau.
The mineralisation is associated with steep dipping, normal faulting orientated along three main directions: N-S, ENE-WSW and ESE-WNW. The character of a lode varies with it's orientation; the N-S lodes generally being broad (up to 80 wide) with poorly defined margins, with the others being narrower (up to 6 wide) with well defined sides. Consequently it was the N-S lodes (particularly the Gors Lode) that first drew attention in the district. The characters of the lodes vary locally as well, with orientation, degree of mineralisation and inclination varying with rock lithology and with intersections with other lodes. The host rocks are cleaved slaty sediments or volcanic tuffs. The faults are believed to be late Caledonian in age (late Silurian to early Devonian) whereas the mineralisation itself is believed to be late Carboniferous or early Permian in Age. Hot hydrothermal fluids passing through the pre-existing fault zones deposited the minerals. No zoning of mineralisation is evident, the minerals present being locally controlled by lithology (typically shales or volcanics) e.g. lead at Cyffty, lead and zinc at Parc, zinc at Aberllyn. There is also a close relationship between dolerite intrusions and mineralisation in the most important mines, although their effects on mineralisation are not fully understood.
Most of the mines are on Forest Enterprise land, which will not allow access. Some of the more important mines have been gated, bared or capped. In the vast majority of cases, the remainder have been fenced off. This is a good thing, because many of the sites are potentially lethal since overgrown shafts and stopes abound. Any area that lies off the trackways should be treated with the greatest of respect. Similarly, underground workings (where accessible) should be treated with caution. Many of the workings, particularly the most recent ones have seriously deteriorated in the last few decades.
Pandora Mine is the only major mine which is accesible, although the contributor is not aware of what the official access status of Pandora is.
The following text is based on the personal journal of Robin Griffiths, and was compiled during extensive site visits in the late 1990's. Although the sites are generally gated, some sites do appear to be open from time to time. Entry is not recommended however due both the access situation and poor state of the mines.
Parc Mine Area
- No 2 Adit SH 7868 5980
- No 3 Adit SH 7877 6015
- No 5 Adit SH 7880 6075
- Fucheslas Deep Adit SH 7863 6009
- Air Shaft & stopes SH 7879 5969
None of the workings are currently accessible. The older workings are flooded or lost whereas the more recent adits have been gated. Prior to being gated, Parc was a popular trip with extensive underground workings, some providing access to older workings. Parc Mine was formed by the amalgamation of older workings on the N-S trending Gors and Fucheslas lodes. During this century stoping along the E-W Principal Lode became the main concern. This was done on the number Two and Three levels for about 2 miles to pass beneath the older Llanrwst and Cyffty workings. Parc is approached by following the forest road south from Nant Cottage.
- Level 3 - Gors Lode
The gated number 3 adit is a prominent feature disgorging ochreous water at the head of an area of 'landscaped' mine tailings. Just below is the smaller arched brick entrance to Adit 4 which is blocked after some distance. The large Number 3 adit was the main haulage level during this century. Both adits were driven south along the Gors Lode. Just to the south of the adits is a large open stope known as Kneebone Cuttings. Nearby is the flooded Gors Shaft which was sunk down a rich pipe of ore to a depth of over 400’. There is a choke dam a short distance up the adit, the purpose of which is to prevent catastrophic flooding should a choke on Level 3 along the Principal Lode fail.
- Hafna Passage
Some 500’ along Adit 3, a fork to the right leads to recent workings on the Hafna Lode. Sections of the passage are heavily silted due to surface tailings being swept in via older workings above. A waterfall enters one of the stopes corresponding with surface shaft on the Reservoir Lode. Heavy silting and a major collapse terminate the Hafna passage.(RG I havn't been able to verify whether this passage is connected to Hafna Mine).
- Parc Shaft
Continuing along the No 3 level, a complex area is reached in the vicinity of the underground Parc Shaft. A circular section of passage surrounds the shaft, and there are extensions southerly and easterly along the Gors and Principal Lodes respectively, whilst to the west are the main 20th century workings along the Principal Lode. The southern extension was driven to within 100' of the Gwaynllifon Deep Adit. Parc Shaft is a large bore (10m square) underground shaft that was driven 220’ below level 3. Nearby is a flooded incline to level 4. There is a large gantry above the shaft in an intermediate level between levels 2 and 3.
- Level 3 Principal Lode
This proceeds westwards as a large access passage in the footwall of the stope. 150’ high stopes lie to the right with ore chutes at regular intervals. Within about 1000’ a small blockage is followed by a major collapse which terminates the level and holds behind it vast tonnages of water. It was possible to bypass the choke from the level 2 adit above.
- Level 2
This is one of the old workings on the Fucheslas Lode and lies 1000’ to the south and some hundreds of feet to the west of the Gors Lode. This reaches the Principal Lode at a junction about 150' above a deep stope). To the east, the Gors Lode is reached. Further to the east again is the remains of the Bidston Tidal Experiment – an attempt to measure the tilting of the earth due to the incoming tide. Just further on is the bottom of the Air Shaft. The Gors Lode is driven southwards for some distance to where the load deteriorated as evidenced by three short passages searching for the lode. Near the junction is an old ladderway shaft which leads to the Parc Shaft gantry. From here a 40’ pitch bypasses the Parc Shaft entering level 3 via an ore hopper.
- Level2 Principal Lode
Every few hundred feet, this passage has deep holes linking it with Level 3 on the right, and holes above and to the left leading to stopes above. About 2500’ in, a pumping shaft from the Llanrwst Mine comes in from above. This is New Shaft, an underground shaft giving access to the main Llanrwst pumping shaft – Endean’s. This still has a large wooden pump rod installed. Further along, the tramway is suspended from the walls by chains, until terminated by absence of a section of floor overlooking a deep stope. During the 1970s a hair raising traverse along an old pipe gave access to Cyffty mine. It was also possible to enter the old Gorlan workings from Level 2.
Some distance back, a ladderway shaft connects level 2 with level 3 on the other side of the blockage. This led through chest deep slime to a 200' ladder shaft upwards rise connecting with the workings of Cyffty Mine.
To the north, are the Fucheslas Deep Adit, No 5 Adit, and other shafts. On the side of the road to the north of No3 adit is a gated adit (Cilsten Mine ?) to limited workings along the Shale Lode. Up the spoil heap from the No2 Adit is a covered shaft (Fucheslas Lode) with section of false floor. Commencing upwards from a similar altitude, but to the east and on the Gors Lode is a series of workings (gated adits) up the hillside of the Fucheslas escarpment. At the base is a deep (estimated 150’+), covered shaft about 10’ square. This is probably be the Parc Air shaft. These workings are probably linked to the stopes above Level 2 on the Gors Lode.
These workings occupy the high plateau area to the south of Parc Mine and are driven mainly along a number of parallel north-south lodes including southerly continuations of the Gors and Fucheslas Lodes – Red Lode and Owen’s Lode respectively. The workings occupy a heavily worked area of spoil and ruined buildings in the forest surrounded by a fence. There are a number of stone lined open shafts in the vicinity of the junction of the New Lode with Sutton’s Lode. The 1200’ long Gwaynllifon Deep Adit, now gated was driven from a point just to the north of Llyn Parc along Sutton’s Lode to intersect the main workings. To the west are fenced off, overgrown surface stopes along the Cobbler’s Lode.
This small sett is just to the north east of Gwaynllifon adjacent to a forest track. It consists of an overgrown, fenced off area. There are a couple of open shafts sunk along the Red Lode.
Ty’n Twll (Clementina Mine)
This mine is just to north of a ford on a wooded hillside between the Llanrychwyn and Trefriw roads. The site is overgrown and fenced off. There are a number of shafts, all overgrown to some degree leading to stopes. At the eastern end is the stone lined, square Engine Shaft. Adjacent to the Trefriw road is the semi-collapsed, but still accessible Adit which leads to the bottom of the Engine Shaft. Given that the lode dips to the east, the westerly surface shafts (which are presumably old workings) must be shallower than adit level. There was also a nearby Roadside Shaft which was not located.
Extensive mine driven on five levels on the Hafna Lode and some workings on the Rabbit Lode. The site which is next to the Gwydyr road is marked by the remains of the Hafna Mill, with it’s fine chimney. All entrances are gated and access is not possible. The most prominent entrances are the Winding Shaft and No. 3 adit which are just above the mill.
Vale of Conwy Mine
Adit No. 2 is in fenced off, overgrown area immediately to the west of the Gwydyr Road between Hafna and Bwlch yr Haiarn and opposite Llanrwst Deep Adit. Adit not properly investigated. Further up, at the base of an escarpment are older workings, the target of the adit. There is another adit below the road which was not found. A path opposite No2 descends passing the Llanrwst Deep Adit to the Vale of Cnowy Mill which has been renovated. There are a number of capped shafts in the vicinity.
Pant yr Ewig
Taking the forest track to the north of Hafna, Pant-yr-Ewig is a fenced off area of spoil to the west of the track. There are a number of shallow looking workings with semi-collapsed adit/shafts leading to a shaft above the most westerly area of spoil.
Minor workings. Not visited
Fridd Sian/ Rhaiadyrwst/ Trefriw Lead Mine
A number of small workings that were later worked as a single unit. Shown in survey in the MOTGF as being about 250’ deep. The workings extend beneath, but are not linked to Pant-yr-ewig.
- Clogwyn Gwlyb SH 7840 6055
A number of trial adits in dense woodland along a steep escarpment to the south of the Rhaiadyrwst stream. At the base of the line of workings is a more substantial looking cutting with a large spoil heap beneath.
- Ffridd Sian SH 7855 6069
A large fenced off cutting amidst dense woodland below Rhaiadyrwst. This is to the west of a forestry road just before it reaches the main Gwydyr road.
- Rhaiadyrwst SH 7840 6066
This small mine is to the north of a stream as it plunges down the steep Clogwyn Gwlyb escarpment. At the head of the escarpment is some stonework which represents the remains of a dam. The workings are fenced off and extend down the escarpment for a distance of about 200’. At the top is a small shaft. Further down are a couple of semi-blocked adits, with an open, but fenced off adit at the bottom.
The following is an extract from Robin Griffiths's 1999 Journal
The Gwydyr Forest mines have been an area of interest for a long time. However, until this year they have been relatively unknown to us. I started a reconnaissance program at the start of summer in order to get the area into some kind of perspective.
The southern part of the district has been pretty well placed off bounds by the Forestry Company and their gating scheme. In contrast, the northern section is still quite accessible. The Pontifex level is in a shallow gully just behind the car park near Llyn Geirionydd and has a half hearted fence around it. My initial surface foray was a look at this before proceeding to the Pandora mine proper. Near the road between Geirionydd and the Cyffty mine is an extensive area of fines. This was the original dressing area for the Pandora mine and lesser mines to the west. Before the Pontifex level was driven, ore from Pandora was taken by a tramway down to Geirionydd. Just across the stream from the tramway is the Netherton level. This was driven to intersect the New Vein, but was never completed.
To the south of the dressing area are two workings on the Talyllyn and Bodgynydd Lodes. The first, known as the Talyllyn Mine is a series of shallow workings and a couple of deeper shafts, including the large bore, square sectioned Bwlch y Groes Shaft which is about 30’. The Loveridge level, which is still open was a crosscut to these workings.
Further to the south again is the Bodgynydd Mine on the opposite side of Bodgynydd Lake. These are mostly shallow, flooded workings.
Walking towards Pandora itself, there are a number of shallow workings on the Champion Lode. These consist of surface stopes and a couple of crosscuts and represent the original Pandora Mine. A compact spoil heap and the remains of zinc and lead separation cells mark the site of Pandora itself. The shafts by which the ore was raised have been filled. It is however possible to enter the Pandora via workings on the Francis Lode.
A few weeks after, John Parker and myself entered the Pontifex Adit. This 450m long adit initially starts thigh deep in water, and gradually shallows until the intersection of the New and Goddard lodes is met at the foot of the Pyne Shaft. Here is a false floor over flooded workings and a large pumping shaft upwards. The workings were originally over 55 fathoms deep (300ft), but are now flooded to the 33 fathom level (180’). We explored stoped workings on the New Lode in both directions. A ladder shaft on this lode as illustrated in the Gwydyr Mines book is now defunct. The ladder has deteriorated and is scattered across the stope.
Onwards are workings on the Goddard Lode. This carries a good draught, which comes from shallow workings on the Francis Lode above. There are a number of ore chutes still intact along the Goddard Lode and in one section an old ladder upwards, which may be the link with the surface.
Myself, and a couple of others did a through trip later that Summer. Entering one of the adits on the Champion Lode, we soon came to a large shaft down to some large stope workings. Another abseil down a large shaft landed in an ore hopper which we slid down to reach the Goddard lode. A wet exit via the Pontifex adit made an interesting through trip.
The mine lies in an area of prominent spoil to the right of the Cyffty to Llyn Geirionydd road. The early shallow workings were based on the Champion and Francis lodes to the south east. There are a number of open workings and two shallow adits. An underground shaft (rigged) connects shallow Francis lode workings with deeper workings on the Goddard Lode. In order to exploit the New and Goddard lodes, a number of shafts were sunk including the Engine (Spion Kop) and Ladderway Shaft. Both of these have now been filled in. Later, the 500m long Pontifex Adit was driven from Llyn Geirionydd to intercept the New Lode. This adit is open but fenced off and is found near the Llyn Geirionydd car park. Near the old tramway is the abandoned Netherton Level, intended to intercept the New Lode.
A prominent series of levels and stopes up the hillside near a promontory on the west side of Llyn Geirionydd.
Not visited. To the north of the prominent Gilvyn Ddu mine on the north west bank of Llyn Geirionydd. Two adits.
This mine is discussed in greater detail in Ogofa 5, Spring 1997. The area consists of a number of adits and shallow shafts along the Geirionydd Gorge between the Klondyke Adit and the Taliesyn monument near Llyn Geirionydd. The lower entrances are levels driven on both sides of the gorge, some with substantial stoping. At the head of the gorge is a line of shallow shafts.
The large main adit is adjacent to the prominent Klondyke Mill at the base of the Geirionydd Gorge. The level has been driven along three parallel N-S lodes although no stoping was undertaken. The following is an extract from an article written in 1997 by Robin Griffiths.
The site of the old Klondyke Lead Mine is dominated by the impressive remains of the old Klondyke Mill. The mine itself consists of one main level adjacent the mill and numerous smaller working following the Geirionydd Gorge upstream, although some of these working are part of the Bryn Cenhadon Mine.
I first visited the site during spring after a visit to the nearby Clogwyn y Fuwch slate mine. On this occasion I just visited the Klondyke Main Adit. The adit numbering system adopted in this article is arbitrary.
On Sunday 1st of December I returned to do a survey. Again I visited the main adit (ADIT 1) which lies immediately across the stream from the mill. The entrance section is quite large and stone lined. The workings basically consist of three passages trending southwards from a cross cut. There does not seem to any great signs of actual lead working despite the fairly extensive passages.
Just upstream from here is the Geirionydd Gorge which is quite a narrow ravine leading up to Llyn Geirionydd. There are numerous small and more extensive workings on both sides of the river here. Small nondescript workings are those Adits marked on the map as numbers 3, 7, 8, 9 and 10.
Adits 2, 3, 4 and 5 are just below some cascades in the river. In fact the entire river drops down a shaft in the river bed and emerges as a foaming cascade from a small mine level (not numbered). Numbers 4 and 5 are linked and lead to a quite large stope which is about 2m high and dips at about 20° to the west. As ADIT 4 enters the stope there is a large timber lined door frame.
ADIT 2 is on the opposite side of the river and is basically a single passage leading to a small stope with a single side branch. The survey shows the passage to go underneath the river onto the opposite bank. This is accomplished because of the climb in river bed above this group of entrances.
ADIT 6 is a short length of passage leading to a square section flooded shaft. The shaft appears to vary from about 5m to about 10m in depth, although it could be deeper. Ladders and old timbers can be seen in the water. It is possible to cross the shaft by crawling on some old timbers, but both branches of the subsequent fork quickly terminate.
ADIT 11 was the most southernmost adit surveyed. This soon enters a steeply inclined, narrow stope with a surface shaft above. Onwards a passage to the left exits to the river bank again. The main passage terminated just after a ninety degree bend where there is a shaft in the roof with a timber frame type structure supporting a pile of deads. The survey shows this point to be in the vicinity of a number of surface workings belonging to Bryn Cenhadon Mine.
Upon surfacing I followed the river upstream again and reached and area containing a large number of 10m deep shaft and stopes in a line parallel to the river. These were not entered on this occasion.
It is interesting to note that most of the passages trend from north to south. Despite the presence of the nearby mill, no stoping is present and not much ore appears to have been won from the Klondyke Adit - it appears to have been a largely unsuccessful prospecting venture trying to intercept the veins that had been exploited in the older Bryn Cenhadon mine further up the gorge. The levels further up the gorge - although smaller in extent have extensive stoping testifying to the ore removed.
The mill itself was built in the early 1900’s and processed ore from the Pandora Mine near Llyn Geirionydd. Ore was transported via tramway and then aerial ropeway to the mill. The Klondyke achieved a degree of notoriety just after the First World War as the scene of an elaborate fraud - See Below.
The ‘Klondyke’ Fraud It seems that during the period 1918 to 1921, the Klondyke was the scene of a massive fraud. The story is related in some detail in Mines of the Gwydyr Forest, but briefly what happened was this. A certain Joseph Aspinall took over the mine in 1918 and claimed to have discovered a huge vein of silver. What he did was to clean the passages of dirt, purchase 20 tons of powdered lead concentrate and glue it onto the walls giving the impression that the entire passage passed through a huge vein of silver. He then bought parties up from London to view the vein and procure an investment in the venture. A mass of miners were employed who actually did no work, let alone any mining. Whenever Aspinall turned up with a viewing party, a hoot of his car horn triggered the miners to busy themselves around the premises - some guarding the adit with cudgels, others running around the place like ants on an ant hill. By the time he was rumbled, he managed to secure £166,000 ! He got 22 months.
South Pandora Mines
These mines – known as Ffridd Talyllyn and Bwlch-y-Groes are to the south of an area of fine spoil - the Wiloughby Dressing Floor to the south of the Cyffty to Geirionydd Road. The most prominent entrance is the square sectioned, large bore Bwlch y Groes shaft which was sunk about 60’ onto the Silver Lead Lode. There are other surface workings and small shafts on this lode. The Loveridge Level which is still open was driven southwards to intercept this lode.
This mine is illustrated on page 17 of this issue of Ogofa. There are a number of small shafts and flooded pools along the Bodgynydd Lode on the southern shore of Llyn Bodgynydd. There is also a fenced off adit to the east of the road, presumably on the same lode.
Cae’r Hegle Mine
Not visited. A number of small mines on the north side of the Crafnant Valley.
Not visited. Shaft and adit to the north west of the South Pandora mines.
Llanrwst Mine Area
This was a large and prominent mine marked by an engine house chimney. Situated at Bwlch yr Haiarn. There are a number of capped and locked shafts none of which are currently accessible. Most prominent is Endean’s Engine Shaft next to the old engine house. On a hillock to the south east is the capped Doctor’s Shaft. Just across the forest track to the east is the gated Shallow Adit and the capped Air Shaft. The capped Footway and Diagonal shafts are in the grounds of the Outdoor Centre. To the right of the road to the north, and just opposite the Vale of Conwy Level 2 adit is the gated Llanrwst Deep Adit. The adit is in an area of extensive surface workings, all overgrown, dangerous and fenced off.
Underground, both the New Shaft (an underground pumping shaft offset from Endean’s) and the Diagonal Shaft were intercepted by the Parc Mine Number 2 level, through which Llanrwst ore was to be extracted, but in the event was never utilised.
The collapsed adit of the Alltwen Level driven to cut the Alltwen Lode lies just across the Llyn Sarnau causeway. Quite a bit of water seeps out during wet weather. Old shafts sunk on the lode itself haven’t been located.
Workings were on the Reservoir and Principal lodes. The only level so far identified is a prominent gated one on the escarpment near the forest road.
The site lies to the west of Llyn Sarnau. Adjacent the car park is a collapsed adit driven along the Principal lode. To the south west the nearby Sarnau cross cut, driven to intercept the same lode is also collapsed. Fenced shafts on the same lode are however still open.
This large mine lies in the Aberllyn gorge between Betws-y-coed and Llyn Parc. The mine was worked for zinc along the Shale lode well into this century and has only recently been gated. Prior to this it was a popular and impressive trip. It is approached via a forestry track from a caravan site on the Llanrwst to Betws-y-coed road. The most apparent surface feature are the large floors visible from the forestry track, behind which the Brunner-Mond haulage level can be followed to the portal of the 6 level.
Further on up the gorge, more entrances can be found, level 4 being the one that was used by explorers. This is to the right of and below the path. The 3a level is just up the path and on the left.
Level 4 commences through some deep sludge. This soon lowers and disappears, and quickly reaches the Cathedral Stope. To the left is the bottom of an open shaft, to the right is the main mine. If followed as far as possible, the 4 level gets underneath Llyn Parc, evidenced by the large amounts of water coming through the roof and walls. Near the end of the Cathedral Stope, a ladder in the left wall goes up to the three level, and another ladder in the right floor descends with water to the 5 level.
Level three is the most complicated, at the Southern end there is access to an open shaft from where daylight is visible. It is also possible to get up to the 2 level by climbing up a shaft from one of the tunnels.
The five level is much wetter than the three level, and can be followed to a collapse near the old 5 adit. There is also a shaft down to level no. 6.
Not visited. On the eastern bank of the River Conwy near Cilcenus Farm. A couple of adits and an open stope.
On the east side of the Conwy River. A series of workings, some substantial adjacent to Cilcenus land. There are a series of adits leading up the hillside with some open stopes and a couple of shafts.
Wheal George/Coed Mawr
Not Visited. A number of adits – condition unknown.
Rhyd y Creau
Not visited. On the east side of the Conwy River. Exploratory workings in and around the Rhyd-y-Creau Gorge.
Griffin Mine & Pen-yr-allt/South D’Eresby Mountain
Griffin Mine consists of a series of gated levels up the hillside behind the Aberllyn mill. Workings on 5 levels. The top, westerly workings are the Pen-yr-allt workings and were originally independent. The Pen-yr-Allt Shaft is sunk to the number 1 level. A large area of spoil on the surface mark the location of Pen-yr-allt. The adit and shafts (No 2 near Penrallt Cottage) have not been approached.
Not visited. A number of trials overlooking Betws-y-coed
Cyffty (Betws-y-Coed Mine, Pencraig Mine)
A prominent restored site opposite the Geirionydd junction of the Gwydyr Forest road. Both the Shallow and Deep adits have been blocked. The Engine Shaft is also blocked whereas the 120’ deep Western Shaft is open but capped. Workings were along the Cyffty and Principal lodes, the later which was also worked at Parc. Parc was connected to Cyffty during it’s final years.
This small mine lies between the Geirionydd road and a forest trackway. The adit is run in, but a couple of fenced off shaft are still open.
Coed Mawr Pool Site
Extensive workings near Llyn Pencraig. I haven't seen any enterable workings but there are some shafts still open. Being beneath the lake, the workings were prone to flooding so a deep adit was driven from the banks of the river Llugwy for over 1km. The adit is fenced and disgorges a great quantity of water into the river. The level commences through neck deep water gradually shallowing. At the end is a choke which is presumably at the base of a shaft as evidenced by a rope and the remains of an old electron ladder. This point is presumably beneath the main workings. Just before this point is a small stope in a vein.The mine is also linked underground to the Ffriddllechwedd workings.
Glyn Llugwy Mine
The wet Deep Adit is a few metres from the A5 opposite the army camp. Another two open, unfenced shafts can be founds by walking uphill near the stream. There may be others hidden away in the undergrowth so beware. The workings are about 1000’ long and are driven along the Main and King’s lodes.
Two shafts near Ffridd Cottage. One is fenced off and near the path between Cyffty and Ffridd Cottage. The other is between the track leading to the cottage and the stream. Linked underground to Coed Mawr Pool.
A small working on the western bank of the Llugwy near the A5 bridge. Workings are believed to be Roman and are fenced off. Adit is open, and there are a couple of semi choked shafts.
Derwen Deg Copper Mine
Cae Coch Pyrites Mine
On the west side of the Conwy Valley near Llanrwst. Igneous sill intruded into shales producing 2m thick orebody of quartz, calcite and pyrite. 90,000 tonnes extracted between 1860 and 1875. Reopened by government during WW1, 1600 tonnes extracted. The oxidised pyrite has been leached by water filling the workings with sulphuric acid which support copious growths of slimy bacteria.
The standard reference work is the seven part book series, 'The Mines of the Gwydyr Forest' by John Bennet and Robert W Vernon.
- Mines of the Gwydyr Forest, Part 1, Llanrwst Mine and it's Meighbours ISBN 0951479806
- Mines of the Gwydyr Forest, Part 2, The Hafna Mine, Llanrwst and some early ventures in Gwydyr Nant ISBN 0951479814
- Mines of the Gwydyr Forest, Part 3, Parc Mine, Llanrwst and Adjacent Setts ISBN 0951479822
- Mines of the Gwydyr Forest, Part 4, Aberllyn Mine, Betws-y-Coed and Adjacent Setts ISBN 0951479830
- Mines of the Gwydyr Forest, Part 5, Coed Mawr Pool, Cyffty and Other Mines in South West Gwydyr ISBN 0951479849
- Mines of the Gwydyr Forest, Part 6, Pandora and Other Mines in North West Gwydyr ISBN 0951479857
- Mines of the Gwydyr Forest, Part 7, Llanrwst: Coed Gwydyr and Cae Coch, Llangelynin: Trecastell and Derwen Deg ISBN 0951479865