Armagh Limestone is probably the most well recognised of Northern Ireland’s limestones, and the second most commonly used. The majority of its usage is within County Armagh, with a small number of buildings in County Down and Belfast. It is a Carboniferous, fossiliferous limestone varying in colour from pale grey to purplish red and was used extensively in Armagh City and the surrounding areas in the 18th and 19th Centuries.
Several of the main stone quarries are still active, although largely used for aggregate. Armagh Limestone shows little decay over time (open porosity 0.37%) with only mild weathering along stylolites, where fossils are present and occasional mortar damage where cement pointing has been used.