Slate

Although some slate was quarried in County Londonderry and on the Rosemount Estate, Greyabbey, the majority has been imported with the most common varieties being Welsh or Penrhyn slate (Bangor Blue) and Westmoreland Slate from the Lake District area. Slate is made up of fine-grained metamorphosed shale sediments which spilts easily into sheets making it ideal as a roofing material. It is generally light to dark and occasionally purplish grey in colour and is usually relatively resistant to weathering