The Pentrefelin slab and slate works were located on a canal wharf, in a narrow strip of land between the north bank of the River Dee and the Llangollen Canal. It is an example of a 'remote' mill, processing material imported from the Bwlch Oernant quarries (NPRN 420091) some 6 kilometres to the north-west, via the Oernant tramroad. Dating from the 1840s, it had at one time eight planers, three circular saws and a sand polisher operated by a 18 ft by 4 ft water-wheel. Although shown on contemporary maps as 'Disused' in 1899 and a 'Rubber Factory' in 1912, it reputedly continued to function as a slate works until the 1920s. This was despite waste tipping problems resulting from complaints about blocking the river. The building is now the site of a motor museum.
Sources:
D.Gwyn, Welsh Slate: the Archaeology and History of an Industry (RCAHMW 2015), p.108-9.
Ordnance Survey County Series 25-inch map: sheet Denbighshire XXXIV.11, editions of 1875, 1899 & 1912.
A.J.Richards, A Gazeteer of the Welsh Slate Industry (1991), p.207.

David Leighton, RCAHMW, 17 June 2015

Other sources:
I.Edwards, `Slate Quarries In The Llangollen District?, Denbighshire Historical Society Transactions 34 (1985), p.95.
R.Martin, ?Changes in the Vale of Llangollen, 1790-1865?, Transactions of the Denbighshire Historical Society 48 (1999), p.65-8.