The Conglog Slate Quarry was opened in 1854, when it was the subject of a temporary permission to extract minerals order, or “take note” from Cwmorthin Ucha farm. One of the partners of the enterprise was Robert Roberts, a surgeon at the Oakeley Quarry hospital at Rhiwbryfdir, and it is assumed that he provided the capital for the venture. By 1868 a 21 year lease had been taken out on the land.
Historians believe it was Robert who provided the initial funds for the formation of this quarry. And so William and Robert took on this task of extracting slate and worked this quarry on their own.
Meanwhile, nearby Rhosydd had been extracting slate up the hill since 1853 and their spoil tips and buildings began to encroach on the Conglog sett. They, Rhosydd, had built their manager’s house, Plas Cwmorthin, on land to the east of Conclog, just outside the leased territory. But in a later, possibly aggressive move, they built a barracks on Conglog land, next to where the mill would be in 1865.
From then on, there would be frequent disputes about land . No written evidence exists that proves whether they had help from other collaborators or completed this task heroically on their own. When the lease agreement was renewed in 1866, Robert was the only name mentioned in this document. And so he went on and formed the Conglog Slate Company.
He had a total of 716,000 square meters of land. It was required of him to pay 2 shillings for every ton of rock he extracted from the quarry.
A total of 250 tons were extracted per year which totaled £25. An extra £5 was required for every extra hectare used for dumping the rock waste. Several years later, in 1865, a number of cottages were built in close proximity to Conglog Slate Quarry, a place named Tan-yr-Allt.
These cottages were used by the workers from the nearby Rhosydd quarry. With time, the Conglog quarry grew even more. It grew so much that with time a dispute arose between these two quarries over a piece of earth found in the south-west part of Robert’s land.
A period later, an agreement was reached. Both companies kept their lands and the disputed area would be used for dumping the rock waste generated by both companies.
The cottages were kept by the Rhosydd quarry. But the agreement stated that the Rhosydd was to give up the cottages if Robert ever wanted them.
Robert went on with his business and even leased a part of this land to T.M. Matthews and W.H.B. Kempe. Kempe and Matthews were required to pay £900 every year plus £2 for every acre they would use as a dumping site.
The pits themselves (four in total) were 18 meters apart. The pits were named A through D beginning with the lowest. The ‘A’ pit was 105 meters wide, though not deep enough to reach a vein. The ‘B’ pit was somewhat bigger standing at 20 meters and reached the back vein. The ‘C’ vein ran a bit to the north and just like ‘B’ also reached the back vein. The ‘C’ pit was the highest and thus the only one that remains open to daylight today. The ‘D’ pit was only a trial dig.
It is believed that that the slate was taken out of the quarry using horses. At a later point, this was done by using a tramway built for this purpose from the materials used in building the Ffestiniog Railway, this tramway was built for the purposes of the quarry, such as transport of materials.
After several more changes of ownership and management, the quarry finally closed in 1910. It had never been a major player, but had it’s moments- 862 tons in 1901, for instance- although production declined steadily then until closure. There was development underground and four chambers were opened out to daylight, now all sadly inaccesible due to collapses. Now, the remains sit evocatively at the head of the cwm, the chambers looming darkly on the hillside.
Today the quarry remains abandoned with its structures continuously being battered by the elements. All of the buildings now stand roofless, crumbling, surrounded by scorched grass and the lonely peaks of the surrounding mountains.