Flagstone

A thinly bedded siltstone or fine sandstone that splits naturally along parallel bedding planes into flat, durable slabs.

Historical usage

The Caithness and Orkney flagstones formed around 370-387 million years ago from mud and fine sand settling on the bed of Lake Orcadie during the Devonian. James Traill began commercial extraction in Caithness in 1758, using windmill-powered pumps to keep quarries workable, and by 1793 flagstone was already being shipped as far as Boston, USA. The industry peaked between the 1850s and 1920s: by 1902 Caithness alone was producing around 35,000 tonnes a year, employing over 1,000 workers across eleven major quarries, with dedicated harbours built at Castlehill and Harrow specifically to export it worldwide -- including, notably, to the Fray Bentos meat-packing works in Uruguay. Cheap mass-produced concrete paving displaced flagstone through the early 20th century and the industry contracted sharply, though quarrying resumed on a smaller scale from 1949 at Spittal, which remains active today.

Value over time

Flagstone's value lay in its ready-made flatness: because it split naturally into usable slabs along its own bedding planes, it needed far less dressing than a stone that had to be sawn to shape, keeping it competitive as a paving material despite the cost of shipping it worldwide by sea. That advantage disappeared once cheap, locally pourable concrete paving became widely available in the early 20th century, and the industry never recovered its earlier scale even after reviving in 1949.

Hazards & challenges

No hazard specific to flagstone itself is well documented; the generic risk of any hard-rock quarrying and dressing is airborne silica dust, carrying a risk of silicosis without proper dust control.

Images

Mines associated with this term

Included only where MineArchive's own research gives a reasonable evidential basis — not every mine where this might plausibly apply.

• Stromness Flagstone Quarries — Orkney (well documented example)
  Named 3 times in this record, first in the history: “The Stromness Flags take their name from the town they helped build: flagstone used to construct Stromness itself was quarried from the shore at…”

See every mine that worked flagstone →

Sources

1. (primary) Stromness Flagstone — Building Stone Database Scotland (British Geological Survey)
2. (secondary) History — A & D Sutherland Ltd

Record created: 27 August 2026 · Last researched: 29 August 2026