Great Rock Mine

Overview

The last working mine on Dartmoor, and one that sold its ore by the shine rather than the iron: Great Rock's micaceous haematite went into the paint on Royal Navy battleships, the Royal Albert Bridge and the Sydney Harbour Bridge.

History

Working began around 1822, at first as the Hennock Iron and Tin Mine on five iron lodes — the Main South, Middle and Beadon lodes and two smaller North lodes. It closed in the late 19th century and reopened in 1902, when the Ferrubron Manufacturing Company took over the iron ore operations of the Teign Valley and kept only Great Rock and neighbouring Kelly at work. Waterwheels drove the plant until the 1920s and electricity did not arrive until 1950. Production peaked at about 2,500 tons a year in the 1940s, when the Admiralty's demand for protective paint was at its height, and labour shortages brought women underground for the first time — Nesta Burton of Hennock was the first woman Ferrubron employed there. The mine closed in 1969, the last active mine in what is now Dartmoor National Park.

Geology

The lodes carry micaceous haematite, an iron oxide that forms as minute greyish-purple flakes with a bright metallic lustre — hence 'shiny ore', a name the Geological Survey ended up adopting from the miners as 'shining ore'. It is chemically the same substance as the massive haematite worked for iron in Cumbria, but its value here had nothing to do with its iron content and everything to do with its shape: flat flakes that lie down flat.

Geological setting: Veins and Lodes (well documented example)

Workings

A complex of adits and levels driven on the several lodes, with waterwheel-driven dressing plant until the 1920s. The ore was ground rather than smelted, and the product left as a powder. Miners were recognisable off shift by the metallic sheen the dust left on their clothes. Before blotting paper, the same powder had a quieter trade as 'pounce' or 'Devonshire sand', shaken over wet ink to dry it.

Closure

Great Rock closed in 1969; the Coal Authority's abandonment plans for the mine are dated 1974. The market it depended on had moved to synthetic pigments, and a small Devon mine grinding flakes by the ton could not follow.

What remains

Abandoned, and treated as an industrial archaeological site rather than an explorable one. Its better-known neighbour Kelly Mine, which worked the same material, survives as a preserved and restored site. The five east-west lodes were worked principally by adits with few shafts, and the adit mouths can be seen from the public footpath; the workings themselves are barred.

Adits, dressing floors and the remains of the processing plant among the woods above the Teign.

Redevelopment

None.

Related mines

• Kelly Mine — The two mines worked the same material (micaceous haematite/ochre); Kelly survives as a preserved site while Great Rock does not.

Recorded claims

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

• Working began at about 1822, initially as the Hennock Iron and Tin Mine, on five iron lodes — the Main South, Middle and Beadon lodes and two smaller North lodes. ^1,2
• The mine closed in the late 19th century and reopened in 1902 when the Ferrubron Manufacturing Company took over local iron ore operations, retaining only Great Rock and Kelly. ¹
• Peak production reached about 2,500 tons a year in the 1940s, much of it for the Navy's protective paint. ³
• Micaceous haematite from the mine went into rust-resisting paint used on Royal Navy ships and on the Royal Albert Bridge and Sydney Harbour Bridge. ³
• Waterwheels powered the plant until the 1920s and electricity did not reach the mine until 1950; during Second World War labour shortages Nesta Burton of Hennock became the first woman Ferrubron employed there. ¹
• Before blotting paper, the same powder was sold as 'pounce' or 'Devonshire sand', sprinkled over wet ink. ¹
• The mine closed in 1969, the last active mine in the Dartmoor National Park area; abandonment plans are dated 1974. ^3,4
• The sett comprises five east-west lodes worked principally by adits with few shafts; these can be viewed from the public footpath but the workings are barred and reported to be very unsafe. ²

Photographs & further reading

Sources

1. (secondary) Hennock — Mining in the Parish — Hennock Parish
2. (secondary) Great Rock Mine, Hennock, Teignbridge, Devon — Mindat
3. (secondary) Great Rock Mine — Wikipedia
4. (primary) Mine plans MP23336, MP23337, KP23343, MP24145, MP24146: Great Rock Mine — British Geological Survey / Mining Remediation Authority mine plans catalogue

Record created: 24 August 2026 · Last researched: 24 August 2026