The now disused Gorseddau Slate Quarry was first opened 1807, but its main period of working was between 1854 and 1857, when it was developed by the Bavarian mining engineer Henry Tobias Tschudy von Ulster. The visible remains include tiered workings and waste tips set into and against a south-west facing hillside. There are remains of an incline and several ruined structures including; the Gorseddau Tramway (NPRN 34663) that was built to connect the quarry with Porthmadog, Ynys-y-Pandy Mill (NPRN 40572) and Treforys Workers Village (NPRN 306319).
Source: David Gwyn & Merfyn Williams (1996) ‘A Guide to the Industrial Archaeology of North West Wales’. Association for Industrial Archaeology
J.Wiles, RCAHMW, 23 September 2003 (edited November 2011)