Derry Schist

Greenish grey in colour with obvious schistose partings. Used for rubble stonework on many buildings in the County Londonderry area. It tends to weather along partings and preferentially deteriorates in the presence of cement mortar.

Extracted from quarries to the SW of Derry city such as Prehen Quarry and Kittybane Quarry 2 to 3 km SSW of the city, most to all of which are now inactive.