Gauge: 1ft 11½in (600mm)
The Blaenau Ffestiniog area produced about a third of Welsh slate during the nineteenth century. No underground working came close to rivalling Oakeley Slate Quarry which was claimed to be the largest slate mine in the world. There were 26 floors from almost sea level to 1500ft and 50 miles of 2ft gauge track underground. One of its underground inclines had no fewer than 6 tracks.
Oakeley Slate Quarry was an amalgamation of three quarries, upper, middle and lower, worked by separate owners, including Samuel Holland, one of the first customers of the Festiniog Railway in 1839. The middle quarry (Gloddfa Ganol) was worked by Nathaniel Mathew and pioneered the use of mechanical slate dressing tools. In 1878 the leases on both upper and middle quarries expired and the landowner, W.E. Oakeley decided to work them himself.
The lower quarry, known as Lord Palmerston had been a spectacular success. It had an output of 50,000 tons per annum, and a workforce of almost 1000. New technology had been brought in and the quarry had an extensive tramway system and connection to the Festiniog Railway. Success had been won at the cost of safety and there had been two huge underground collapses which had damaged Oakeley’s quarries above. Following legal action Oakeley bought out the owners of the Lord Palmerston and amalgamated all three quarries under his own name. The damage and the downturn in trade during the 1880s meant that the Oakeley Quarries were never as profitable as one unit as they were previously. Nevertheless they held their position as the third largest producer in Wales with an output of some 60,000 tons a year.
An extensive steam loco worked surface tramway served the nine mills. Inclines gave access to the Festiniog Railway and later directly to the mainline railway. Steam power was extensively used for bringing up slate, pumping and operating the mills. Electricity began to be introduced after 1906.
The quarry was profitable up until the 1960s when the market was again lost. It closed in 1970, but was reopened as two separate units, Gloddfa Ganol and Ffestiniog Quarry. A tourist visitor attraction and Railway collection were also operated on the site. in 1997 the site was acquired by Alfred Macalpine Slate and the tourist operation closed. Vigorous extraction recommenced and it was planned to use the waste rock at Oakeley as building material. There are an estimated 100 million tonnes of waste rock at the quarry and current production is increasing this at the rate of 2 million tonnes a year.
Together with McAlpine's other slate interests in North Wales, it was sold to a firm named Rigcycle (linked to the Irish construction group Lagan) in December 2007
Diana Kerr, Stuart & Co. No. 1158 of 1917; 0-4-0 tank. Sold to Pen-yr-Orsedd 1945