Devon County Geological Sites

Site reference no. SX59SE1 Name: Meldon (Red-a-ven) Mine

District: Dartmoor National Park, Parish: Okehampton Hamlets West Devon National grid ref: 57009175 OS sheets: 1:50k 191 1:25k OL28 1:10k SX59SE GS 1:50k 324

GridRef x y Lat Long SX57009175 257000 91750 50.707751 -4.0266117

Locality description (address): Beside the Red-a-ven Brook and its tributary about 750 metres SE of Meldon Viaduct.

Nature of site: A disused mine, probably only a trial, with a filled shaft, small dumps, a partly collapsed adit and the remains of a wheal pit. There are exposures of the ore body in the Red-a-ven Brook and the adjacent tributary.

Geological / geomorphological features: The minerals worked at Meldon Mine is mainly exposed on small dumps. The one surrounding a filled shaft is composed of a dark fine-grained pelitic hornfels, probably with incipient growth of cordierite weathering out as raised spots, grey weathering recrystallised chert and grey limestone , some of which occurs as a granular aggregate of calcite crystals. Fragments containing skarn minerals including, wollastonite, axinite, diopside, the calcium garnets andradite and grossularite. The tin-bearing sphene analogue, malayite has also been found Pyrrhotite with pyrite and chalcopyrite occurs on the dumps close to the Red-a-ven Brook. The exposure in the Red-a-ven brook shows beds of hornfelsed mudstone and chert dipping north west at about 550 . These enclose rusty weathering lenses up to 0.5 metres wide and reaching over 5m in length over a width of about10 metres. The lenses appear to be mainly of pyrite which is tending to decompose in places, the presence of pyrrhotite can be detected by its magnetism. There is some chalcopyrite and löllingite. The workings date to about 1839, when they were noted during the first geological survey of South West England.

Reasons for registration as a County Geological Site: This site, which is related in its mineralogy to Ramsley, with an interesting range of skarn minerals and sulphide ores, has also yielded the rare tin-bearing sphene, malayite. It is also of particular interest in showing the outcrop of the ore body which is not seen elsewhere.

Site sensitivity: This site is believed to be popular with specialist mineral collectors looking for malayite. At present it does not seem to be to be being greatly disturbed.

Safety: Generally safe

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

Access and Parking: Direct access from the Meldon Quarry road through a gate and by a well defined track between the ‘Granulite Quarries’. This is not indicated as a public footpath but is in frequent use to reach access land. The mine is outside the boundary of the MOD range area. The exposure in the Red-a-ven Brook may not be accessible from the east bank if the stream is high. Parking is available in places on the Meldon quarry road, care is needed because of heavy lorries. Some cars have been seen parking near the old granulite quarry buildings but this is not a public parking area

Date of assessment (V = visited) : V 14th May 1998 R T Taylor

Site owner : Common (Access) Land – Duchy of Cornwall.

References: DEARMAN, W.R. and Butcher,N.E., 1959. The geology of the Devonian and Carboniferous rocks of the north-west border of the Dartmoor-Granite, Devonshire. Proceedings of the Geologist’s Association. Vol.70, pp.51-90. EL SHAKARWI, M.A.H. and DEARMAN, W.R.,1966. Tin-bearing skarns from the from the north-west border of the Dartmoor Granite. Economic Geology. Vol. 61, pp. 362-369. EDMONDS, E.A. and others. 1968. geology of the Country around Okehampton. Memoirs of the Geological Survey of Great Britain. London, Her Majesty’s Stationary Office