Penarth Slate Mine, Corwen

Penarth Slate Mine, also known as Penarth Slate Quarry, is located above the village of Carrog near Corwen in Denbighshire, Wales. It is part of the Cambrian slate belt that runs through the Dee Valley and played a modest but important role in Wales’s 19th and early 20th-century slate industry.

The quarry likely originated with small-scale workings before the mid-19th century. However, significant development began around 1868, coinciding with the arrival of the railway in the area. This allowed Penarth to expand its operations and transport slate more efficiently. A narrow-gauge tramway and incline linked the quarry to the Penarth Slate Wharf on the Ruabon–Barmouth railway, improving access to broader markets.

By the early 1870s, the workforce had grown to around 150 men, and slate was extracted through a mix of open terrace workings and later underground chambers. However, production levels fluctuated, and by 1883, only about 10 men were employed, producing approximately 500 tons annually. The quarry first closed in 1890 due to financial difficulties but reopened in 1895. By 1898, the workforce was back up to 50, and output increased to around 1,700 tons in the early 1900s.

As the mine expanded underground, it adopted more advanced machinery. Initially, slate was dressed by hand, but by the early 1900s, water- and oil-powered sawmills had been introduced. A sawmill at the railway wharf used water-powered sand-saws. In 1904, modernisation continued with the installation of a 12hp Blackburne oil engine and a later 40hp Hornsby gas engine to power air compressors and cutting machinery, including a rare reciprocating oil-powered shot-saw.

Despite these improvements, the quarry never matched the scale of North Wales’s larger operations like Penrhyn or Dinorwig. Penarth ultimately specialised in slate slabs rather than roofing tiles, and by the time of its final closure in 1932, production had dwindled to around 1,000 tons per year.

Today, the site is abandoned but retains substantial remains, including the drumhouse, incline, mill buildings, sawmill remains, and dressing sheds. Underground, the mine features multiple flooded and collapsed levels, chambers, and inclines—some of which are still explored by urban explorers. Locals sometimes refer to the mine as “Dragon’s Breath” due to the warm air that flows from its tunnels.

Although now largely reclaimed by nature, the Penarth Slate Mine remains a fascinating glimpse into the industrial heritage of the Dee Valley. Its story is preserved in part by the Corwen Museum, which features exhibits on slate mining in the region. While the site is unsafe for casual visitors, it continues to capture the interest of historians and enthusiasts alike, reflecting a broader chapter in Wales’s once-thriving slate industry.

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Cambrian Slate Mine, Llangollen

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Keele Railway Tunnel