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Situated on the eastern side of the Carn Marth granite this district has been an important producer of copper ores in the past having produced some 1.25 million tones of copper concentrates. Additionally it has been a producer of tin ores mainly associated with rhyolite dykes, one such mine Wheal Jane only closed in 1990.
Symonds map.
Wheal Jane today


The country rock is of metasediments cut by ENE to WSW trending rhyolite dykes dipping mainly to the north, and fissure lodes of a similar trend but dipping both north and south. Many of the mines in the area have been the subject of supergene enrichment producing rich copper ores. Substantial amounts of placer tin have been recovered from the Carnon Valley and have also been recovered from Restronguet Creek by underground mining from well below sea level.
After Dines, 1956.
  Other ores of lead and zinc with minor wolfram and small amounts of gold have also been produced. North-south crosscourses crosscut the district and are clay filled and occasionally mineralized with galena and marcasite.

Wheal Jane in the 1970s
Mount Wellington
Wheal Jane mine was reopened in 1966 although early production had taken place at outcrop in small opencast operations from as early as 1740. The main part of mineralization, occurring mainly on the footwall, is closely associated with a ENE-WSW trending rhyloite dykes which extends for over 3 km and includes the Mount Wellington Mine. However, one part of the lode system is entirely in metasediments. The mine produced not only tin but also a large tonnage of zinc concentrates and minor copper with contained silver.

The rhyolite dykes in the mine often have chilled margins and the occasional xenolith of granite indicates the near proximity of granite at depth. A concealed granite ridge probably extends out from Carn Marth.

Xenolith of granite

The mineralization is polyphase, in a shear zone, and is extensively brecciated. The average ore grade was 1.0 %Sn but with zinc grades exceeding 5%.

Wheal Jane ore
Underground surveying
Wheal Jane lode



Three main phases of mineralization recognised are:

1) Greisen mineralization with wolframite, cassiterite and lollingite.

2)  An early phase of tourmalinite-tin mineralization. This has been recognised in the footwall of the dyke and may predate some dyke emplacement and occurs as breccias.

3) Chlorite-sulphide assemblage of abundant pyrite and sphalerite and minor chalcopyrite, stannite and arsenopyrite with fluorite, quartz and chlorite as gangue minerals.

A deep phase of oxidation has been recognised in the mine by the discovery of silica bubbles containing copper rich fluids, a vapour phase, and detached relic fluorite crystals.

Fluorite and amythyst
Aerial view of the Carnon Valley
In the Carnon Valley below Wheal Jane Mine cassiterite has been recovered from gravels deposited by rivers at periods of lower sea level. These are now covered by estuarine silty-clays and tailings from mining operations up-stream. Mining operations here commenced in prehistory and continued up to the 1980s.
Carnon Valley


It was in working these deposits that the largest nugget of gold found in Cornwall was recovered in 1808. Further downstream in the Restonguet Creek tin bearing basal gravels were recovered by underground mining. This was effected by sinking shafts on land, extending tunnels out just below the bed of the creek and rising up to extract the basal gravels and retreating as the overlying silty clays settled to close up the excavation. These mining operations included Carnon Mine and the Restronguet Mine.
Carnon Nugget
Camm et al. 1981
Carnon Mine
Drawing of Carnon Mine
Plan of Restronguet Mine
Near the contact with the Carn Marth granite at St Day lies Wheal Gorland Mine. This mine and the adjacent mine of Wheal Unity are world famous for the variety and rarity of the secondary minerals found during mining.
Plan of Wheal Gorland
The minerals were found near the contact zone with granite in the zone of oxidation and supergene enrichment. As the ore was rich in both copper and arsenic, many arsenates of copper, iron and lead have been found. Little remains of the surface workings today, the dumps having been removed to recover the cassiterite contained in them.
AfterLeBoutillier, 2003

Wheal Gorland today
Clinoclase and liroconite

For more information on Wheal Gorland and historic photographs please see this link

Other virtual geological field excursions in PDF files are for:

West Penwith, (2.83MB)

Marazion to Porthleven, (1.22MB)

Porthleven to Polurrian, (0.67MB)

The Lizard, (2.11MB)

St Austell Area, (1.40MB)

East Cornwall, South Devon and Dartmoor. (1.73MB)

Click on the one you wish to visit and download.



This site was last updated on Monday, October 17, 2005 8:41 AM .
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