Slate Workers in Hendreddu chamber 1920s
Photographic Archive Tywi Mountain
Hanes y Goedwig, Erwyd Howells
'The Carved Slates of Dyffryn Ogwen 1830...
Nantlle Valley and slate quarries
Penrhyn Quarry
Penrhyn Slate Quarries, Bethesda 1904
Pharmacy minerals