16/06/2026
πͺ¨ The pavements of Victorian London were paved with Caithness stone. The flagstones under the feet of Edinburgh's New Town, the pathways of cities across the British Empire, the courtyard floors of institutions whose architects demanded something flat and durable and permanent β much of it came from a remote corner of the far north of Scotland where the geological accident of near-perfect horizontal cleavage in the local sandstone made the production of flat flags a natural operation rather than a difficult one.
Caithness flagstone is an Old Red Sandstone formation of the Devonian period, laid down approximately three hundred and seventy million years ago in the shallow lakes of a semi-arid landscape that would become the far north of Scotland. The sandstone was deposited in thin horizontal layers under specific conditions of seasonal flooding and evaporation, and those conditions produced a stone that splits naturally along its bedding planes into slabs of remarkable flatness, consistency, and durability. The fossil fish preserved in some Caithness flagstone beds β the extraordinary Devonian fauna documented by Hugh Miller β were deposited in the same lake sediments that produced the industry.
The flagstone industry at Castletown and across Caithness reached its peak in the mid-nineteenth century, when the demand for urban paving across Britain and the empire coincided with the development of shipping routes that could carry heavy stone from the far north coast economically. At its height, dozens of quarries were operating across Caithness and thousands of tons of flags were exported annually from small harbours whose modest scale belied the global reach of their trade.
The quarries are now largely silent. Concrete replaced flagstone for most purposes in the twentieth century. But the Caithness flags are still there, under the feet of London and Edinburgh, outlasting the industry that laid them.