Merstham Chalk Mines

Overview

Underground stone mines worked into the North Downs escarpment at Merstham for perhaps a thousand years, supplying the calcareous 'firestone' building stone used at Westminster, Windsor Castle and Old St Paul's — and, in 1868, the site where Alfred Nobel gave a public demonstration of dynamite.

History

Merstham's underground stone workings are believed, from archaeological and documentary evidence, to have been worked continuously from the 7th or 8th centuries until 1961 — one of the longest working lives of any mine in Britain. The mines were driven into the Upper Greensand, the bed of soft, calcareous sandstone known locally as firestone or Malm stone, which outcrops along the North Downs escarpment through Godstone, Bletchingley, Merstham and beyond; the stone is soft when freshly dug and must be seasoned and laid in the same orientation it lay underground if it is to last. Merstham firestone supplied some of medieval England's grandest building projects — the king's palace at Westminster in 1259, Windsor Castle in 1359, and Old St Paul's Cathedral and London Bridge. Operations were important enough in the Middle Ages that the mines were taken into Crown ownership, and the Prophete family controlled working here through the 14th century. The Croydon, Merstham and Godstone Iron Railway, an extension of the Surrey Iron Railway — itself the world's first public railway — opened in 1805 to carry stone and lime from Merstham to Croydon by horse traction, closing around 1840 as the London to Brighton railway was being built. As building tastes and transport improved through the 18th and 19th centuries and other building stones became more easily available, the underground stone trade at Merstham declined, reviving only on a smaller scale as a source of hearthstone, used for whitening doorsteps, stone floors and hearths. In July 1868, Alfred Nobel gave a public demonstration of his newly invented dynamite in one of Merstham's chalk quarries, at Price's Grey-lime Stone quarry.

Geology

Merstham's mines were driven into the Upper Greensand, a calcareous, iron-stained sandstone (locally 'firestone' or Malm stone) that outcrops along the foot of the North Downs chalk escarpment from Godstone through Bletchingley and Merstham; the overlying chalk itself was also worked, for lime.

Workings

Worked as underground galleries following the firestone bed, on a pillar-and-stall pattern typical of soft-rock stone mining, rather than as open quarries; some sections show Roman-period stone-cutting characteristics, evidence of the site's exceptionally long working life.

Closure

The underground stone trade declined from the 18th century as transport improved and other building stones became easier to source, surviving latterly as a smaller hearthstone trade before the last workings finally closed in 1961.

What remains

Extensive underground galleries survive beneath Merstham and the neighbouring escarpment, some explored and recorded by caving groups; a section of the trackbed of the 1805 Croydon, Merstham and Godstone Iron Railway is preserved and displayed near Quality Street, Merstham.

A preserved section of the 1805 horse-drawn tramway's track is on display near Quality Street; capped shafts and underground galleries survive elsewhere around the village.

Abandoned workings can be dangerous — unstable ground, uncapped shafts, flooding and bad air are common even where a site looks safe from the surface. This entry describes history and general location only; it is not an access guide.

The underground workings are hazardous and not open to casual access — this entry describes history only, not an access guide.

Recorded claims

Individual factual claims, each attached to the source(s) that support it below. Where sources disagree, both are kept.

• Archaeological and documentary evidence indicates the stone mines were worked from the 7th or 8th centuries until 1961. ¹
• Merstham firestone was used at Westminster in 1259, Windsor Castle in 1359, and Old St Paul's Cathedral and London Bridge; the mines were important enough to be taken into Crown ownership in the Middle Ages. ¹
• The Croydon, Merstham and Godstone Iron Railway, an extension of the world's first public railway, opened in 1805 to carry stone and lime to Croydon by horse traction, closing around 1840. ²
• Alfred Nobel gave a public demonstration of dynamite in Merstham's Price's Grey-lime Stone quarry in July 1868. ²

Sources

1. (primary) Parishes: Merstham — Victoria County History (British History Online)
2. (secondary) History of Merstham — Reigate and Redhill Society

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