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Penberthy Croft Mine, St Hilary, Mount's Bay District, Cornwall, England, UK

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Latitude & Longitude (WGS84): 50° 8' 25'' North , 5° 25' 19'' West
Latitude & Longitude (decimal): 50.14028,-5.42222
UK National Grid Reference:SW555324
Köppen climate type:Cfb : Temperate oceanic climate
Other regions containing this locality:Devon and Cornwall metalliferous mining district, England, UK


Penberthy Croft mine is situated approximately one mile northeast of the village of Goldsithney in the parish of St. Hilary, Cornwall, England (NGR SW 555 324). The locality is a prolific source of rare and unusual secondary minerals of which the Cu-Pb-Fe-Al arsenates are the best known. Penberthy Croft is the type locality for the following species: the copper lead arsenate bayldonite and the aluminium arsenates bettertonite and penberthycroftite.

Penberthy Croft is the first, or joint first recorded site for the tin hydroxide minerals jeanbandyite and natanite in the British Isles. Segnitite is also first recorded at this location.

The land is owned by the St. Aubyn Estate. Permission for site visits and bona fide research must be made prior to any visit through the Agent for the St. Aubyn Estates. The address is Manor Office, Marazion, Cornwall, TR17 0EF, England. Telephone: +44 (0) 1736 710507.

History:


The mine is quite ancient and records of output give approximately 3000 tons of copper ore toward the end of the 18th century. Mixed copper and tin mining took place at depth at a later date, the lodes being stoped out to a depth of 53 fathoms below adit level. The mine closed around 1840. There being no further activity until recent years when at a time of high tin prices the dumps were sampled to evaluate their cassiterite content. The mine became listed as a SSSI by English Nature for its mineralisation in 1993.

Geology:


The sett is situated in Devonian metasediments consisting of lower-grade-greenschist facies (killas) slates between the Land's End and Godolphin granite masses. The slates belong to the Mylor Slates Formation and are a series of dark coloured rocks with a slaty cleavage and well-developed foliation. They are generally characterised by a series of siltstones and mudstones, with occasional impersistent sandstone sequences. A series of interbedded metabasic rocks strikes east-west within the sett. The main Penberthy lode strikes east-west and dips to the south. The lode is associated with a rhyolite porphyry elvan dyke and cross course structures and is probably related to a shear zone. There are in addition five other named lodes within the sett.

Mineralisation:


The mineralisation is of a multi-stage, polymetallic and hydrothermal character. The deposit consists of several, but distinct overlapping assemblages: Minor, burial-related quartz-albite-anatase-monazite veins of a pre-tectonic, metamorphic origin; main-stage high-temperature hypothermal-mesothermal Sn-Cu-As-W veins; later lower-temperature epithermal Pb-Zn sulphide mineralisation; and a late-stage, low-temperature Fe-Mn mineralisation. Subsequent supergene oxidation and weathering of lodes resulted in the formation of complex gossans with oxide and supergene enrichment zones. Post-mining formation of other minerals both underground and on the dumps has resulted in a very large variety of mineral species in a small area. These in order of approximate abundance include arsenates, arsenate-sulphates and phosphates. The greatest diversity in terms of species has been located in five main areas of the old dumps: Three in the western and two in the eastern section of the workings. Most minerals here are found as good quality subhedral to euhedral microcrystals with occasional miniature specimens. Brecciation, fracturing, silicification, chloritization and carbonatization are abundant. The mineralisation formed over a very wide period of time extending from the Upper Palaeozoic through to the Cenozoic.
A major comprehensive mineralogical study was recently completed on this important locality by Betterton (2000) and was published in the UK Journal of Mines & Minerals, 20, 7-37.

Note on the mineral list:


Reference to adamite at Penberthy Croft is from Kingsbury. Given the doubts about the provenance of other Kingsbury specimens (Ryback et al. 1998, 2001), investigated this and discredited the occurrence.

Unknowns (UK PC = Unknown Penberthy Croft) from the John Betterton Collection under investigations:
UK PC2 ? MnxOx
UK PC3 ? Cu+Zn+As+Mn+Fe+Co??+La???+O
Additional work is required on these unknowns.

Mineral List

Mineral list contains entries from the region specified including sub-localities

Adamite

Agardite-(Ce)

Agardite-(La)

Alloclasite

Anatase

Anglesite

Ankerite

Annabergite

'Apatite Group'

Aragonite

Arseniosiderite ?

Arsenolite

Arsenopyrite

Atacamite ?

Aurichalcite

Azurite

Bayldonite (TL)

Beaverite-(Cu) ?

Beraunite

Bettertonite (TL)

Beudantite

Bieberite

Birnessite

Bismuthinite

Bismutite

Bornite

Brochantite

Bulachite

Calcite

Caledonite

Carminite

Cassiterite

Cattiite ?

Ceruleite ?

Cerussite

Chalcoalumite

Chalcophyllite

Chalcopyrite

Chamosite

'Chlorite Group'

Chrysocolla

Churchite-(Y) ?

Clinochlore

Connellite

Copper

Corkite

Cornubite

Cornwallite

Covellite

Cuprite

var: Chalcotrichite

Cyanotrichite

Devilline

Dolomite

Duftite

Dundasite

Erythrite

Fluorapatite

Galena

Goethite

Gypsum

Halite

'Halloysite'

Hidalgoite

'Hornblende'

Jarosite

Jeanbandyite

Langite

Laurionite

Leadhillite

Lepidocrocite ?

Libethenite

Linarite

Liskeardite

Malachite ?

Mansfieldite

Mattheddleite

Millerite

Mimetite

Mixite

Monazite-(La)

Mottramite

Natanite

Olivenite

var: Leucochalcite

Orthoclase

Paratacamite ?

Parnauite

Penberthycroftite (TL)

Pharmacoalumite

Pharmacosiderite

Philipsburgite

Phosgenite

Pitticite

Plumbogummite

Plumbojarosite ?

Pseudomalachite

Pyrite

Pyromorphite

Quartz

Redgillite

Rosasite ?

Scheelite

Schulenbergite

Scorodite

Segnitite

Serpierite

Siderite

Silver ?

Smithsonite

Sphalerite

Stannite

Stilpnomelane

Stolzite

Sulphur

Tenorite

Tyrolite

Vanadinite

Varlamoffite

Woodwardite

Wroewolfeite

Wulfenite

Wurtzite ?

Zálesíite

Zincolivenite


112 valid minerals. 3 (TL) - type locality of valid minerals. 8 erroneous literature entries.

Geochronology

Geologic TimeRocks, Minerals and Events
Phanerozoic
 Paleozoic
  Permian
   Guadalupian
ⓘ Major polymetallic mineralization~270 MaCornwall, England, UK
   Cisuralian
ⓘ Porphyry dikes intruded (latest age)~275 MaCornwall, England, UK
ⓘ Greisenization (latest age)~280 MaCornwall, England, UK
ⓘ Porphyry dikes intruded (earliest age)~280 MaCornwall, England, UK
ⓘ Formation of metallized pegmatites~285 MaCornwall, England, UK
ⓘ Greisenization (earliest age)~285 MaCornwall, England, UK
ⓘ Emplacement of major plutons~295 MaCornwall, England, UK

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Late Devonian
358.9 - 382.7 Ma



ID: 2033495
Upper Devonian Rocks (Undifferentiated)

Age: Late Devonian (358.9 - 382.7 Ma)

Lithology: Mudstone, siltstone and sandstone

Reference: British Geological Survey. DiGMapGB-625. British Geological Survey ©NERC. [23]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License


Localities in this Region

UK
  • England
    • Cornwall
      • Mount's Bay District

This page contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.

References

Kingsbury, A.W.G. (1954) Transactions of the Royal Geological Society of Cornwall, vol. 18, part 4 (for 1952), p. 392 + 395.

Dines, H.G. (1956) The metalliferous mining region of south-west England. Economic memoirs of the Geological Survey of Great Britain.

Kingsbury, A.W.G. and Hartley, J. (1956) Atacamite from Cumberland and Cornwall. Mineralogical Magazine, vol. 31, n° 235, 349-350.

Kingsbury, A.W.G. and Hartley, J. (1957) New occurrences of arseniosiderite. Mineralogical Magazine, vol. 31, n° 237, 499-500.

Kingsbury, A.W.G. (1957) New occurrences of phosgenite. Mineralogical Magazine, vol. 31, n° 237, 500-501.

Kingsbury, A.W.G. and Hartley, J. (1957) New occurrences of rosasite in Britain. Mineralogical Magazine, vol. 31, n° 237, 501-502.

Kingsbury, A.W.G. and Hartley, J. (1960) Carminite and beudantite from the northern part of the Lake District and from Cornwall. Mineralogical Magazine, vol. 32, n° 249, 423-432. (referring to Kingsbury 1954).

Goode, A.J.J. and Taylor, R.T. (1988) Geology of the country around Penzance. British Geological Survey, London.

Betterton, J. (1989) Birnessite from Penberthy Croft - a Second English Occurrence. Journal of the Russell Society: 2, (2), 48.

Camm, G.S. and Merry, M. (1991) Bayldonite and its associates from Penberthy Croft, Cornwall. UK Journal of Mines & Minerals, vol. 9, 6-15.

Rust, S.A. (1995) Bismutite from Penberthy Croft Mine, St. Hilary, Cornwall. UK Journal of Mines & Minerals: 15: 18.

Betterton, J. (1996) Monazite-(La) and Anatase from Penberthy Croft Mine, St. Hilary, Cornwall. UK Journal of Mines & Minerals: 16: 13.

Betterton, J. (1996) Tenorite from Penberthy Croft Mine, Cornwall. UK Journal of Mines & Minerals: 17: 18.

Betterton, J. (2000) Famous Mineral Localities: Penberthy Croft Mine, St. Hilary, Cornwall, England. UK Journal of Mines & Minerals: 20: 7-37.

Ryback, G., Hart, A.D., and Stanley, C.J. (2001) Journal of the Russell Society: 7, Part 2.

Moulding, D., Hooper, J., and Green, D.I. (2008) Stolzite from Penberthy Croft Mine, St Hilary, Cornwall. Journal of the Russell Society, vol. 11, 88-90.

Braithwaite, Richard S.W., Green, David I., and Tindle, Andrew G. (2009) The distribution and composition of adamite and zincolivenite in the British Isles. Journal of the Russell Society: 12: 3–9.

Grey, I.E., Kampf, A.R., Price, J.R., and Macrae, C.M. (2015) Bettertonite, [Al6(AsO4)3(OH)9(H2O)5]·11H2O, a new mineral from the Penberthy Croft mine, St. Hilary, Cornwall, UK, with a structure based on polyoxometalate clusters. Mineralogical Magazine 49: 1849-1858.

Grey, I.E., Betterton, J., Kampf, A.R., Macrae, C.M., Shanks, F.L., and Price, J.R. (2016) Penberthycroftite, [Al6(AsO4)3(OH)9(H2O)5]·8H2O, a second new hydrated aluminium arsenate mineral from the Penberthy Croft mine, St. Hilary, Cornwall. Mineralogical Magazine: 80: 1149-1160.

Grey, I.E., Brand, H.E.A., and Betterton, J. (2016) Dehydration phase transitions in new aluminium arsenate minerals from the Penberthy Croft mine, Cornwall. Mineralogical Magazine: 80: 1205-1217.

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