Historical reference: Do not rely on this information. It is very old. About this collection
Flagstone, a rock belonging to Lower Silurian series, so laminated that it naturally splits into thin layers or flags suitable for paving. This is a characteristic of certain sandstones, limestones, and indurated clays. Among the best known are those in Caithness and at Fcstiniog in North Wales. In common language a "flagstone" is any flat stone used for paving.