Derry Chalk

Also known as Antrim Chalk this Cretaceous limestone is fine-grained, white, and very hard with an open porosity of around 4%. Antrim chalk is very brittle, fractures heavily in situ and contains numerous bands of flint nodules. Thus it is generally unsuitable for building but is occasionally seen as quarry-faced stone blocks on buildings along the County Antrim coast and in Moneymore (County Londonderry). Almost all of the original quarries are now inactive.