Narrow Vein Mudstone Formation facts for kids

Quick facts for kids Narrow Vein Mudstone Formation Stratigraphic range: Hirnantian Age
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 / 52.6757; -3.8230
Region	Mid Wales
Country	Wales
Extent	Dinas Mawddwy to Tywyn

The Narrow Vein Mudstone Formation is a special layer of rock found in Mid Wales. Geologists call it a "group" because it's a sequence of similar rock layers. This formation was created during the Ordovician period, which was a very long time ago!

The rock in this formation is mostly mudstone. Mudstone is a type of rock made from hardened mud. It can be smooth or have very thin layers. The Narrow Vein Mudstone is usually a medium blue color. For many years, people have dug up this rock to use it as slate.

This rock layer is quite thick, ranging from 400 metres (1,300 ft) to 560 metres (1,840 ft). It stretches across Mid Wales, from a town called Dinas Mawddwy all the way south-west to Cardigan Bay near Tywyn.

Where Can You See It?

You can see the Narrow Vein Mudstone Formation in several places in Mid Wales. These spots are called "outcrops," which means the rock layers are exposed at the surface. This often happens where old glaciers carved out valleys. You can especially see this rock in the old quarries along its path.

Digging for Slate: Quarrying the Narrow Vein

The Narrow Vein is one of the two main types of slate rock in Mid Wales that people dug up for money. The other is called the Broad Vein. The Narrow Vein rock is generally easier to split into thin pieces than the Broad Vein. This made it perfect for making things like roofing slates for houses.

People dug for slate from the Narrow Vein in many places:

• At Bryn Eglwys, where they also worked with the Broad Vein. This quarry was connected to the Talyllyn Railway.
• At Gaewern and Braichgoch quarries in Corris Uchaf. These were linked to the Upper Corris Tramway.
• The Aberllefenni Quarry was used for digging slate from the 14th century until 2002! They also worked the Broad Vein here. It was connected to the Corris Railway.
• Cymerau Quarry was connected to the Ratgoed Tramway.
• Ratgoed quarry mostly dug up the Narrow Vein and was also connected to the Ratgoed Tramway.
• Hendre Ddu quarry was a smaller operation linked to the Hendre-Ddu Tramway.
• Gartheiniog quarry was also connected to the Hendre-Ddu Tramway.