Great Carnon Stream Works

Overview

The most important tin-streaming operation in Cornwall in its day, working the tin-rich alluvial gravels of the Carnon Valley and Restronguet Creek by damming back the tidal water and working the exposed streambed beneath. Around 150 men and boys worked the site at its peak in 1797, recovering both tin and, as a valued by-product, small grains and occasional nuggets of alluvial gold, before a severe gale and exceptionally high tide breached the dam in 1812 and ended the operation for good.

History

The Carnon Valley's tin-bearing gravels have been worked since prehistory: tin and gold from the valley have been identified, through modern isotope analysis, in the Nebra Sky Disc, a Bronze Age artefact found in Germany, and an antler pick recovered from the valley in 1790 was later dated to the Early Bronze Age. In the medieval and early modern periods, streamers here and along the wider Restronguet Creek and Helford catchment routinely recovered small amounts of alluvial gold alongside their tin, and petitions were made to Henry VIII drawing attention to the effect tin-streaming was having on the depth of water available to shipping. By the eighteenth century the lower Carnon Valley and Restronguet Creek had become the site of the most important stream works in Cornwall, worked in five successive attempts: the first two by embankment, damming back the tidal water to expose the streambed beneath, and the last three — including the later Carnon Mine of 1824 — by mining under the water itself. The Great Carnon Stream Works was the more intensive of the two embankment operations, at its height in 1797, when around 150 men and boys were employed there; the 1805 Ordnance Survey preliminary map shows workings running from a bridge near Carnon Downs downstream as far as the later Old Carnon Mine. Dykes were cut into the rocky shore on the Carclew side and a smaller channel on the Devoran side, the spoil used to build the dams that held back the tide while the exposed ground was worked down under a strong central dam; experienced tinners assessed the ore while boys wheeled material away in barrows. Small grains of gold, known locally as prill and usually no bigger than a pinhead, turned up regularly in the workings and were treated as a customary worker's perquisite rather than the operator's property; the largest single nugget recorded from the site weighed around 18 grams. The operation ended in 1812, when a severe gale combined with an exceptionally high tide breached the dam and flooded the works; it was not reopened, and the site's tin-bearing ground was instead worked from 1824 by the very different, underwater method of the new Carnon Mine.

Workings

An embanked, open working: dykes cut into the shore on both the Carclew and Devoran sides of the creek, with a strong central dam holding back the tidal water while the exposed streambed beneath was dug out and the tin- and gold-bearing gravel washed and sorted.

Closure

Ended in 1812 when a severe gale and an exceptionally high tide breached the dam and flooded the works; not reopened as an embanked operation, though the same tin-bearing ground was later worked from 1824 by the shaft-mining Carnon Mine, using a different method to reach beneath the water rather than exclude it.

What remains

No structure survives above ground from the embankment operation itself; the creek has long since reclaimed the site, and the valley's tin-bearing history is instead marked today by the surviving engine house of the later Carnon Mine nearby.

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.

Recorded claims

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

• Tin and gold from the Carnon Valley have been identified through isotope analysis in the Nebra Sky Disc, a Bronze Age artefact found in Germany; an antler pick recovered from the valley in 1790 was later dated to the Early Bronze Age. ¹
• Streamers in the Carnon Valley and wider Restronguet Creek and Helford catchment routinely recovered small amounts of alluvial gold alongside tin from the medieval period onward; petitions were made to Henry VIII about the effect of tin-streaming on shipping draught. ²
• By 1797 around 150 men and boys were employed at the Great Carnon Stream Works, the more intensive of two successive embankment operations in the lower Carnon Valley; an 1805 Ordnance Survey preliminary map shows workings from a bridge near Carnon Downs downstream to the later Old Carnon Mine. ³
• Small grains of gold, called prill and usually no larger than a pinhead, were recovered regularly and treated as a customary worker's perquisite; the largest recorded nugget weighed around 18 grams. ³
• The works ended in 1812 when a severe gale combined with an exceptionally high tide breached the dam and flooded the site. ³

Images

Sources

1. (secondary) Carnon River — Wikipedia
2. (secondary) Later Mineral Workings — Feock Parish Council
3. (secondary) The Great Carnon Stream Works — Feock Parish Council

Record created: 26 August 2026 · Last researched: 26 August 2026