‘Scrabo Sandstone’ is probably the best known building stone in Northern Ireland. It is well known both for its beauty and variety for carved detail and for its relatively poor performance as a building stone in polluted environments.
Scrabo is part of the Sherwood Sandstone Group. This geological formation outcrops around the Newtownards area and within the Lagan Valley with some occurring near Cookstown in East Tyrone and in County Londonderry. Sherwood Sandstone was formed during the Triassic Period 248 to 206 million years ago. The sediments were formed at a time when deserts and tropical oceans prevailed and the British Isles occupied the position of where Sudan is today. During this time flood events deposited sand and silt to produce the sandstones and mudstones seen today.
Given these climatic conditions, some of the stone types of this geological formation are iron-rich and red in colour, red Sherwood Sandstone was quarried mainly in Dundonald, County Down and to a smaller degree in Dunmurry, Belfast and Whiteabbey Shoreline, County Antrim. Dundonald Sandstone is included under the heading ‘Red Sandstone’ along with the other Permo-Triassic red sandstone varieties used as building stone throughout Northern Ireland.
Other Triassic sandstones such as Scrabo and Cookstown Sandstone are buff to pink in colour