Llwyngwern Slate Quarry dates from at least 1835, when Simon Cook of Llwyngwern is listed as a `Slate proprietor?. By 1853 the Mining Journal describes the working as `a long-neglected quarry now reopened? and lists it as having a 30ft. diameter waterwheel. The Llwyngwern Slate Quarry Co. Ltd. was formed in 1863 and by 1878 the concern was working as the Llwyngwern Slate and Slab Quarry.

The Ordnance Survey plan of 1888 shows that most of the fundamental elements of the quarry were already extant: The stream had been dammed to form a reservoir and was presumably culverted beneath the workings to emerge at the bottom of the waste tips, close to the bottom of the present railway; a large processing mill had been built, with a waterwheel against its southeast corner providing power for the slate dressing machinery; a range of cottages had been erected to the east of the mill. The quarry pit itself extended over the western part of the present `hole? and probably down to approximately the level of the mill, as it was accessed via a level tunnel, through which ran a tramway. A magazine was situated in the woods to the north - west of the mill.

Over the next two decades the workings were expanded and by 1900, 144 men were employed and the undertaking was working as Maglona Quarries Ltd. The quarry had been sunk below the tunnel level, the pit being drained by a lengthy new tunnel driven from near the bottom of the present railway; the point where this emerges can still be traced. The short tunnel from the mill level still exists and emerges into the quarry half-way up the sheer rock face! The Ordnance Survey plan of 1901 shows the routes of the tunnels. It also shows the access tramway from the Corris Railway that ran along the opposite side of the main valley. The branch tramway was built in 1896 and crossed the valley on a substantial slate rubble embankment that can be seen today. When it reached the foot of the tips, an inclined plane connected it to tramways on the mill level. The present railway follows the route of the incline. The mill had been considerably extended to the southwest.

By the end of the nineteenth century, the disposal of waste rock was becoming a problem. The Ordnance Survey map for 1901 shows that tipping was being carried out on the south side of the valley, at a level just below that of the reservoir dam. In 1906 a ropeway was constructed from a point just east of the cottages, up onto the southern slope and the tipping of waste material commenced at this level. The lower anchorage can still be found, as can the remains of the engine house high on the hillside. A bailiff's inventory for 1910 included two steam engines to power `Sawing Machines? and `Overhead Tramway?. The same list incidentally, included a 40 foot by 3 foot waterwheel.

The quarry continued to be worked at a much reduced level through the 1920s and 30s, the workforce varying between ten and thirty. Working was discontinued in 1941 and although attempts were made to reopen during the 1950s, the remaining machinery was scrapped in 1959 and the buildings were allowed to fall into ruin.

The quarry is now the site of the Centre for Alternative Technology (see NPRN 302254).

Claire Parry, RCAHMW. 14 June 2011.