Tanybwlch slate quarry is located close to the village of Rachub (NPRN 419797), north of Bethesda, at the foot of Moel Faban. It was established in about 1805 and continued in sporadic use, including as a cooperative, until 1911. Rock was uphauled from a pit and reduced in a small mill. Later some underground working took place from the pit when the Cornish manager, Michael Williams, and the local overseer, John Griffith, sank a shaft and installed a beam engine to wind at some stage between 1865 and 1873. Two steam engines were used. The constricted nature of the site made tipping a problem. A drainage level from the workings is said to have emerged near Llanllechid church. Material was initially carted but a later connection to the Moelfaban incline was possibly made (NPRN 420102). Tonnage is not thought to have exceeded 550 per annum.
Remains (in 1991) included buildings in re-use, much tipping, abutments of two rubbish run bridges, a stockyard piled with finished product, an unusually large engine house with adjacent (filled) shaft measuring 4.6m by 41m on plan, stone lined. It is not clear where the second steam engine - presumably for saw power - was sited.

Sources:
D.Gwyn, Welsh Slate: the Archaeology and History of an Industry (RCAHMW 2015), p.154.
A.J.Richards, A Gazeteer of the Welsh Slate Industry (1991), p.24.

D.Leighton & N.Vousden, RCAHMW, 11 March 2015