Under the microscope, Caithness Flagstone reveals its finely layered structure, with low porosity and minimal water flow. Formed around 390 million years ago during the Devonian Period, when Scotland was near the Equator, it consists of mud and fine sand deposited in the Orcadian Basin. Tightly packed, it has been used for centuries in masonry, paving, and roofing, becoming a key part of Caithness' construction heritage. | British Geological Survey