CN303

Gorseddau Slate Quarry  

12/10/1998  

Designated  

Gwynedd  

Dolbenmaen  

257232  

345275  

Transport  

Quarry  

Post Medieval/Modern  

The following provides a general description of the Scheduled Monument. The monument consists of a slateworks, dating to the 19th century. It was developed with considerable capital according to the best practice of the day, but failed to find a good slate vein and was not subsequently redeveloped or worked over. A small quarry at Gorseddau was offered for sale in 1836, but it began to develop in 1854 under the ownership of Robert Gill and John Harris and with the arrival of the German mining engineer Henry Tobias Tschudy von Uster. The quarry was opened out on the gallery system first developed at Penrhyn Quarry, whereby a spinal counter-balance incline connected a sequence of terraces from the top of the quarry to the bottom. Each terrace contained a quarry gallery, rubble tips, slate trimming sheds, and trimming waste tips beyond. The quarry was served by its own railway to its magnificent slab mill at Ynys y Pandy (scheduled as Gorseddau Slate Factory CN160) and thence to Porthmadog. A village for the quarry workers, Treforys, was built nearby. It was said of the quarry, "everything that could facilitate the works was produced, nothing being wanted but the slate vein". It operated for probably only twelve years, and closed for good in 1871. The quarry features include the remains of the quarry faces, the incline, a drainage adit, waste tips, barracks, stock yards, railways, gwaliau for hand splitting roofing slates, and blast shelters. The monument is an outstanding example of a mid nineteenth-century quarry layout and has a remarkable history of ambitious investment and financial disaster. It is of national importance for its potential to enhance our knowledge of 19th century slate production and industrial practices. It retains significant archaeological potential, with a strong probability of the presence of associated archaeological features and deposits. The structures themselves may be expected to contain archaeological information concerning chronology and building techniques. A slateworks may be part of a larger cluster of monuments and their importance can further enhanced by their group value. The scheduled area comprises the remains described and areas around them within which related evidence may be expected to survive.