Part two of our continuing adventures around Aberllefenni...
Last time, we had come down from the East side of Foel Grochan in failing light, and had gazed (from a respectful distance) at the famous "Alma Cavern", a deep abyss quarried vertically into the mountain. We left, vowing to return and explore further...
Of course, exploring here is discouraged. A mine historian friend had warned me to be careful, as he had been caught by the landowner while underground, and it wasn't a pleasant or decorous meeting. So we were on our mettle when we returned on a very misty, damp day, the sort of weather that is a speciality in these parts.
We'd scoped out an entrance halfway up the mountain that would get us in to the mine, so made our approach under cover of the dense spruce woods that cloak the south side of Foel Grochan. There's a rough but official footpath that goes through there, if you don't mind climbing over countless wind-felled trees. Hard hats on, lamps and back-up lamps checked, we walked carefully in. The usual thrill of being underground hit us; the cold atmosphere, the sounds of water dripping and an all-pervading smell of damp rock.
We walked on through a well-engineered tunnel, past stacked waste, until we came to a section that had obviously become unstable. Massive RSJ's were formed into a supporting arch. For a while, we had begun to sense light ahead. Now we could see that it was a chamber...the big one. We emerged into a scene reminiscent of the "Lord of the Rings" as a mighty hall rose up hundreds of feet to the surface and uncertain light. Below, rubble and huge blocks of slate punctuated the descent- a similar number of feet into total blackness. Eerie skeins of mist swirled through the chamber like ghost dragons. A ladder dangled crazily down, inviting the explorer to certain death. Because of the light coming from above, moss cloaked the wet surfaces everywhere- it was a wonderful ecosystem for them.
We carried on into the mountain, walking probably more than a third of a mile in the blackness, punctuated occasionally by more chambers opening out. Some were flooded, blocked off with wire and corrugated iron, some just with a ledge and an old wooden crane hanging above an impenetrable black abyss. I wondered what the old miners thought, as they worked in these places. Was there a sense of the incredible spaces they were creating, or was it just a job, another day to be got through? I'd hate to think that they were oblivious to the incredible monuments that they had made to themselves here, in the middle of the mountain.
Eventually, we found ourselves at the top of a ladder that descended into a deep chamber. It was claustrophobic and unpleasant, difficult to get a sense of the height as you looked down. I knew what was at the bottom anyway; a crane, sitting over another, deeper chamber. Despite Petra and I having been in a great many mines, this one had started to freak me. I began to have a sense of impending doom- we had been underground for a few hours; perhaps the dark was getting to me. There are plenty of shots of the crane at the bottom of the ladder on the 'net and I decided that we didn't need to add to them. The strain of keeping vigilant against the many perils underground had begun to tell on us. It was time to come out.
So, we turned back, feeling weary, but very happy to have explored such an uncanny and awe-inspiring place. It doesn't seem enough to say that I was impressed by the spaces created in the mountain by the miners. Working men, highly skilled, using primitive tools until the last few years. Later, Korfmann chain saws and wire saws took over, making the job more accurate and producing less waste; although requiring a whole new set of skills to be learnt.
There are rumours that this place is to be developed as a tourist attraction- stories abound locally. It would certainly be a shot in the arm to the local economy, and it seems a shame that people can't see these wonderful caverns and marvel at the skills of the men who made them. It will be a different experience, a changed place, but nothing could take away from the majesty of the "Alma Cavern".
It's incredible to think that slate was being quarried here from the C14th! - so quarrying/mining was carried on continuously until 2003, a world record. Extraction was achieved by boring eight adits separated by approximately 60 feet (18.3 m) vertically. These were mined into the valley side just to the north of the near-vertical narrow vein. Each tunnel bored into the hards at the side of the vein, opening up chambers which formed as the rock was extracted. These chambers ranged from 100 to 187 feet (30.5 to 57.0 m) in length with 24 to 30 feet (7.3 to 9.1 m) of rock left between the bottom of one chamber and the top of the next lower chamber. As more slate was extracted, several of the upper chambers were joined vertically to form an extremely large cavern known as "Twll Golau" (light hole) or alternatively, the "Alma Cavern" which is open at the top. This cavern goes down into the mountain to about 800 feet depth. As with most mines on the Corris narrow vein, the oldest workings are near the top, as mining continued down the vein. A look at the sectioned drawings of the mine show many vertical chambers, almost hollowing out the mountain at some points.
The mine certainly had it's vicissitudes over the years, but was a major player in the Corris area. In approximately 1860, the owner of the mine commissioned a steamship, the 83 foot long "Aberllefenni Quarry Maid" with a steam engine built by DeWinton of Caernarfon- possibly the first marine engine built by them. The quarry outputs were high for the area, with 4,814 tons in 1883, with 177 men employed. In 1893, tonnages were up to 4,044 with 193 men per year, then 5,185 tons in 1895- with only 140 men, the tonnage per man/year being extremely high by local standards.
After the Great War, with export markets non-existant, the market for slate withered, slowly picked up, then was knocked on the head again by the second great conflict. It was never to recover to pre war standards, although there was a steady demand. But worker's conditions and wages then became a sore point, culminating in a strike in 1947. The men found work elsewhere, constructing forestry roads. By the time the dispute was settled, the quarry were lucky to get the men back, as seen elsewhere, workers had become used to higher wages for easier, less dangerous work- and most quarries struggled to get a workforce.
Finally, the last years saw technological improvements, as have already been noted. The new wire saws improved productivity so that the waste rock to product ratio was up to 1-3, as opposed to 1-67 in force during most of the quarries' life! Getting slab was ever more difficult owing to the depth of the chambers, the way that they became wider as they went down- and the fact that short-sighted operations in earlier years had "sterilised" chambers by tipping waste into them. Chambers that could have been worked with modern equipment. But it was always thus. So, the story closes on this fantastic mine- but the mill, at least, is still producing slate from other quarries at the time of writing, December 2018.
Richards, Alun John (1994). "Slate Quarrying at Corris". Gwasg Carreg Gwalch. ISBN 0-86381-279-1.
Ray Gunn's lovely photographs and monologue: "Aberllefenni Quarry" here
Here's a shot, sadly not mine, of the Alma Cavern from across the valley, showing the sheer size and depth of the operation. Bear in mind that the big cavern descends down from the top hole to a couple of hundred feet below the bottom of the valley surface level! Under Foel Crochan cc-by-sa/2.0 - © Michael Graham - geograph.org.uk/p/4939486
If you enjoy my content, please consider supporting what I do. Buy me a coffee! Thank you :-)