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Penrhyn Quarry: relict areas, quarry hospital and underground levels is an industrial quarry in Wales, protected by Cadw under reference CN416. The site exploits the Upper Cambrian bedrock beneath, which includes Tremadoc sandstone and conglomerate formed during the Tremadocian period. These interbedded rocks provided the raw material that drove extraction at scale from the nineteenth century onwards.
The quarry's surviving features reveal the infrastructure of industrial slate production. Relict areas of the worked landscape remain visible, testament to the scale of excavation undertaken across the site. An on-site hospital building documents the hazardous conditions faced by quarry workers, whilst the underground levels preserve the engineering solutions developed to access and extract stone at depth. These voids represent the most intensive phase of quarrying activity.
The monument stands as evidence of Wales's dominant role in global slate supply during the industrial period. The geological character of the Tremadoc strata—their natural jointing and composition—made them particularly suited to working into roofing slates and other products. The physical remnants of quarrying infrastructure, from surface workings to underground chambers, illustrate both the technical demands and the human toll of large-scale mineral extraction.
Penrhyn Quarry: relict areas, quarry hospital and underground levels is a scheduled monument protected by Cadw under reference CN416. View the official record →
Penrhyn Quarry: relict areas, quarry hospital and underground levels is an industrial quarry in Wales, protected by Cadw under reference CN416.
Penrhyn Quarry: relict areas, quarry hospital and underground levels dates from the industrial period, and is classified as a quarry. It is one of over 32,000 scheduled monuments protected across the UK.
Penrhyn Quarry: relict areas, quarry hospital and underground levels is a Scheduled Ancient Monument, legally protected by Cadw — the body responsible for designating and safeguarding heritage sites in Wales. The official designation reference is CN416.
Several scheduled monuments lie within 10 km, including Carnedd Fach cairn (3.7 km), The Holyhead Road: the Ogwen Pass (4.4 km), Nant Ffrancon Anti-invasion Defences (4.7 km).
This page is just one thread. A full Aubrey report pulls together 13 strands of Penrhyn Quarry: relict areas, quarry hospital and underground levels's history, each drawn from the record and mapped to the exact spot:
Every location is different. Not every section appears for every place, only what the historical record actually holds turns up in a report.
Penrhyn Quarry: relict areas, quarry hospital and underground levels stands on Upper Cambrian, Including Tremadoc, bedrock that formed in the Tremadocian. The rock here is sandstone and conglomerate, interbedded.