County Geological Site

Site reference no. WSX46NE2 Name: George and Charlotte Mine

District: West Devon Parish: Gulworthy

National grid ref: SX45236993 OS sheets: 1:50k 201 1:25k 108 1:10k SX46NE GS 1:50k 337

GridRef x y Lat Long SX452698 245200 69800 50.507478 -4.1844472

Locality description (address): George and Charlotte Mine, Monwellham Quay.

Nature of site: Disused mine, now reopened and extended underground as a mining heritage attraction. Surface remains include overgrown dumps, shafts and a dressing floor.

Geological / geomorphological features: An old copper mine working an irregular lode with a quartz-chlorite gangue containing chloritised slate fragments and pyrite, chalcopyrite, rare galena, and irregular cavities lined with the very rare phosphate mineral, childrenite. The mineralogical, depositional sequence is unusual with cassiterite and pyrite formed before chalcopyrite. The characters of the lode are very well displayed in the cleared and maintained Deep Adit level, which opens onto the east bank of the Tamar around 300 yds north of Newquay. Slopes opening up from the adit provide further opportunities to study the lode and associated branches. The return passage for the installed touristic mine train in addition shows an excellent and relatively clean transect through the country rock (Tavy Formation, Upper Devonian) with a range of structural features such as tension gashes, folds and cleavage. Whim Shaft intersects the adit at around 70 m E of the river and was the main shaft for lifting ore from mine to an area of dressing floors above. The dumps here show abundant pyrite, with vein quartz, chlorite and rare childrenite. The mine is reputed to have yielded the largest known crystals of the latter and is the probable type locality of the synonymous ‘Tavistockite‘. Tenorite, galena, sphalerite, haematite and rare cassiterite are also recorded. Old records (unconfirmed) suggest that antimonite and bismuthinite may also have been present. Notably arsenopyrite appears to be absent or very rare.

Reasons for registration as a County Geological Site: George and Charlotte Mine is the only preserved mine in the Tamar Valley and as well as providing safe opportunities for scientific study underground (subject to Mines and Quarries safety legislation) it is unique in that managed public access is promoted, as part of a visit to the Monivellham Quay heritage site. Crucially, however, the lode worked has an unusual sequence of formation and has yielded a number of rare minerals including the largest known crystals of childrenite in the world. The type locality of this mineral was either the Canal Tunnel or Wheal Crebor, but as exposures at these sites are now virtually inaccessible, George and Charlotte Mine represents the most important surviving site for the mineral in its type area.

Site sensitivity: Management of the underground workings ensures that key geological features are not threatened or destroyed.. Surface features such as dumps, which are limited in extent, could be at risk if collecting is not managed appropriately .

Safety: The adit is subject to mines and quarries legislation and access is therefore only normally permitted as part of a guided tour of the Morwellham Quay heritage site. Surface workings include shafts and steep slopes that may therefore present a hazard.

Interest groups: Schools. Years 5-11: Years 12-16: Years 17-18. University. Undergraduate - Research Professional geologists - Amateur geologists - General public.

Access and Parking: Parking is available for visitors to the Morwellham Quay heritage centre and a visit to the mine is included within the price of entry. No other access is normally permitted to either underground or surface features, for obvious safety considerations, excepting by prior arrangement for bone-fide study.

Date of assessment (V = visited) : V Aug 2004

Site owner :

Other: Link: http://www.tvia.org.uk/pages/miningtincopper.shtml

References: BULL. B.W. 1982. Geology and Mineralogy of an area around Tavistock, SWEngland. Unpublished PhD thesis, University of Exeter, pp.119, 175, 178, 211, 218-220; BOOKER, F. AND EMERSON G. 1990. Morwellham Quay: George and Charlotte Copper Mine. (folded leaflet). Monivellham Quay, Devon; COLLINS, J.H. 1892. A handbook to the mineralogy of Cornwall and Devon. (2nd edition, Reprinted 1969). D.B. Barton, Truro. 108pp; DINES, H.G. 1956. The metalliferous mining region of South-West — Volume 2. Memoirs of the Geological Sun/ey of Great Britain, England and Wales. HMSO. London, pp.676-677; EMBREY, P.G. And SYMES, R. 1987, The minerals of Cornwall and Devon , British Museum (Natural History) and the Mineralogical Record lnc., pp.58, 100;