Narrow Vein Mudstone Formation
| Narrow Vein Mudstone Formation | |
|---|---|
| Stratigraphic range: Hirnantian | |
The Aberllefenni Quarry showing the main working of the Narrow Vein | |
| Type | Group |
| Unit of | Abercorris Group |
| Underlies | Garnedd-Wen Formation |
| Overlies | Broad Vein Mudstone Formation |
| Thickness | 400 metres (1,300 ft) to 560 metres (1,840 ft) |
| Lithology | |
| Primary | Mudstone |
| Other | Slate |
| Location | |
| Coordinates | 52°40′33″N 3°49′23″W / 52.6757°N 3.8230°W |
| Region | Mid Wales |
| Country | Wales |
| Extent | Dinas Mawddwy to Tywyn |
The Narrow Vein Mudstone Formation (commonly known as the Narrow Vein) is an Ordovician lithostratigraphic group (a sequence of rock strata) in Mid Wales. The rock of the formation is silty, homogeneous or finely-laminated mudstone. It generally a medium blue colour. This formation has been commercially quarried as slate in several locations along its length. The formation is between 400 metres (1,300 ft) and 560 metres (1,840 ft) thick and runs from Dinas Mawddwy south-west to Cardigan Bay at Tywyn.