Ancient Monuments

History on the Ground

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Gorseddau or Ynysypandy Slate Factory

A Scheduled Monument in Dolbenmaen, Gwynedd

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Latitude: 52.968 / 52°58'4"N

Longitude: -4.1599 / 4°9'35"W

OS Eastings: 255044

OS Northings: 343369

OS Grid: SH550433

Mapcode National: GBR 5N.K3YW

Mapcode Global: WH55D.2NCH

Entry Name: Gorseddau or Ynysypandy Slate Factory

Scheduled Date:

Source: Cadw

Source ID: 2439

Cadw Legacy ID: CN160

Schedule Class: Industrial

Category: Slate mill

Period: Post Medieval/Modern

County: Gwynedd

Community: Dolbenmaen

Traditional County: Caernarfonshire


The magnificent remains of a slate mill erected between 1855 and 1857 as part of the Gorseddau Quarry complex. The building is of three storeys and attics. The tramway bringing raw materials in entered on the upper floor, and slate waste was removed by a tramway from the middle floor; the processing was done on these two floors. The middle floor lies mostly on solid rock, and the lower floor, because of the nature of the sloping site, consists of only one quarter of the mill floor area. The wheel-pit lies in the centre of the building, and originally contained a 26 ft diameter pitch-back wheel.

The building is now a stone shell, with no internal fittings or roof. The terrace which carried the incoming tramway is well preserved, and the bases of the stone pillars which supported the aqueduct are visible.

The monument is of national importance for its potential to enhance our knowledge of the slate industry. It retains significant archaeological potential, with a strong probability of the presence of associated archaeological features and deposits. The structures themselves may be expected to contain archaeological information concerning chronology and building techniques.

The scheduled area comprises the remains described and areas around them within which related evidence may be expected to survive.

Source: Cadw

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