This research explores the cultural geologies and global circulations of Welsh slate before, during, and after its extraction from the mountains of North Wales. The social and language-based histories of Welsh slate are well covered in the literature and are now becoming integrated into the bid to UNESCO for World Heritage status for the slate-producing landscapes of Gwynedd, North Wales. However, the subterranean and off-site geographical, social, technical and aesthetic legacy of Welsh slate is less understood. This research aims to gain a greater understanding of these global impacts of Welsh slate through a multi-disciplinary mapping of the connections that slate is involved in across the world.