The quarry was a remote site; it was nearly 4 miles (6.4 km) to north-east of Duffws, the Festiniog Railway's terminus in Blaenau Ffestiniog.

The land on which it was located was owned by Lord Newborough, and small scale working of the site by local people needing roofing materials was carried out in the eighteenth century.

More organised working of the site began in 1812, by two men from Penmachno and Ysbyty Ifan, which gradually developed into a five-man partnership.

[1] The quarry was located in the parish of Penmachno, and the finished slates were exported by boat down the Conwy River.

[2] In order to get the slates to the river, they used an old trackway, previously used by drovers taking their cattle to markets in England.

[5] In the meantime, Rhiwbach built a wharf at Porthmadog in 1861, and carriage of their slates on the Ffestiniog Railway was first recorded in 1863, when 3,964 tons were transported.

Some slate was exported via the Ffestiniog Railway in 1918, despite the fact that the quarry was officially closed, and the First World War legislation concerning labour still applied.

It reduced the distance that the men had to walk, rather than eliminating it, as the climb from the Cwm Machno quarry to Rhiwbach was too steep for the lorry to negotiate.

There are five main veins of Ordovician slate which pass through Blaenau Ffestiniog, longitudinally (from east to west).

Immediately to the east of the Cwt y Bugail main adit, the strata are cut by the Dolwyddelan fault.

The same two veins re-appear at Rhiwbach, 0.6 miles (1 km) further to the south east, at a considerably lower altitude.

[11] New underground workings were started in 1899, to the east of the main mill, and the incline to raise the slate was again powered by the Injan Fawr.

There were barracks with two or three bedrooms, but whereas some larger concerns such as the Dinorwic quarry provided such accommodation free of charge, the men at Rhiwbach had to pay rent of between 2s 4d and 5s 8d (12p and 28p) per month.

It shows that the "Barracks Mawr" consisted of two-storey buildings, and that there were workshops in the centre of the hamlet, while the schoolroom was constructed of corrugated iron.

From there, slates could be loaded into river boats for onward transfer to Conwy, or directly into sea-going vessels.

This in turn gave the Rhiwbach quarry a rail link to Portmadoc, a major port on Cardigan Bay.