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markbeckett
Joined: 06 Oct 2016
Posts: 41
Location: Cornwall
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Posted: May 15, 2017 11:43 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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Goethite from Wheal Drea, in the Kenidjack Valley, St Just District, Cornwall (also known for its excellent Siderites).
Mineral: | Goethite |
Locality: | Wheal Drea, Kenidjack Valley, Saint Just, Cornwall, England / United Kingdom | |
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Dimensions: | 9cm x 8cm |
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24307 Time(s) |
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markbeckett
Joined: 06 Oct 2016
Posts: 41
Location: Cornwall
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Posted: May 15, 2017 12:08 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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Thought I would post this - for interest's sake more than rarity - Gypsum from Levant Section of Geevor Mine, found growing on the ochreous flooded floor of a stub-drive on Providence Lode, during the final years of the mine. The miners discovered it as it 'crunched' underfoot and lined the whole floor. A post-mining mineral occurrence of note.
Mineral: | Gypsum |
Locality: | Levant Mine, Trewellard, Saint Just District, Cornwall, England / United Kingdom | |
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Dimensions: | 7cm x 4cm |
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_________________ Ex Camborne School of Mines
Grad - B.Eng. Geol. (1993)
'if you see a strange hill, go and prospect there'...(KFG Hosking) |
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markbeckett
Joined: 06 Oct 2016
Posts: 41
Location: Cornwall
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Posted: May 16, 2017 11:53 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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Also, for interests sake, here is a specimen of Native Silver fine wires and curls from 'Whiteworks', also known as Wheal Maid, United Downs, nr St Day, Cornwall. The bricked-up entrance seals a steel-arched, spiral decline into old mines drained by pumping at Wheal Jane nearby and was once hoped to provide a 'drive-in, drive-out' exit for the then existing Wheal Jane operations. My last visit, years ago, saw the water-table had risen way up the decline, effectively blocking any attempt to re-enter. The killas is highly altered to a white/grey sericitic, sometimes soft consistency, and you come out of the mine 'plastered' with much whiteish clay!
I think this is why it has been known as Whiteworks for so long.
This chance occurrence of Silver there was discovered in a clay-filled 'crosscourse'-type fracture. The 'wires' of the metal were completely admixed with the soft clay, that has now been removed. Mr P. Oldfield of St Just, may well have been the first to discover this - the rest was quickly removed by other collectors. There was also a lot of coarse Cassiterite to be collected at Whiteworks.
Mineral: | Silver |
Locality: | Wheal Maid, Gwennap, Camborne - Redruth - Saint Day District, Cornwall, England / United Kingdom | |
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Dimensions: | 2 or 3 grams |
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24216 Time(s) |
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markbeckett
Joined: 06 Oct 2016
Posts: 41
Location: Cornwall
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Posted: May 17, 2017 08:35 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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Quartz - Great Perhaver Beach, Gorran Haven (on the Roseland Peninsula), Cornwall
This coastal location is rarely visited by collectors, probably partly due to the fact that the tide has to be quite low to access it. The geological formation that is partially exposed in the back-beach at Perhaver is a part of the 'Roseland Breccia Formation', a mid to late Devonian, thrusted sedimentary 'melange' containing many giant fragments or 'olistoliths (many up to 10 metre size, some smaller, some much larger). Many of the olistoliths are of Ordivician Quartzite and host brittle-fracture quartz veins. These two pieces were part of a find I made there in 1988. These crystals are probably in excess of 400 million years old. They are a part of the oldest sedimentary rocks in Cornwall. The melange (or 'olistostrome') is a member of the 'Gramscatho Group sedimentary rocks.
Cherry-red Sphalerite can also be found in some of the cliff slide material, though appears to be rare there.
Mineral: | Quartz |
Locality: | Great Perhaver Beach, Gorran Haven, Saint Austell, Cornwall, England / United Kingdom | |
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Dimensions: | 10cm x 5.5cm |
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24095 Time(s) |
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markbeckett
Joined: 06 Oct 2016
Posts: 41
Location: Cornwall
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Posted: May 17, 2017 08:38 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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Another
Mineral: | Quartz |
Locality: | Great Perhaver Beach, Gorran Haven, Saint Austell, Cornwall, England / United Kingdom | |
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Dimensions: | 6cm x 6cm |
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markbeckett
Joined: 06 Oct 2016
Posts: 41
Location: Cornwall
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Posted: May 17, 2017 09:35 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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Datolite with Calcite - Parc Bean Cove, Mullion, Lizard Peninsula, Cornwall.
Datolite in Cornwall is very rare, apart from at the Parc Bean Cove location, that has now been lost, as boulders,to the sea. The matrix is of a highly altered basic igneous rock. This location definitely hosted the best examples in Cornwall.
Mineral: | Datolite with Calcite |
Locality: | Parc Bean Cove, Mullion, Lizard Peninsula, Cornwall, England / United Kingdom | |
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Dimensions: | 4.5cm x 3cm |
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24108 Time(s) |
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markbeckett
Joined: 06 Oct 2016
Posts: 41
Location: Cornwall
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Posted: May 20, 2017 07:39 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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Photos taken underground at South Crofty Mine (Tin) before its closure in the early1990's. This group shows an occurrence of coarsely crystalline Scheelite, associated with Wolframite in Northern Branch lode. After photographing the scene specimens were extracted by careful drilling. Its good to see an actual 'Lode' captured forever in these images - many thanks to P.Oldfield of St.Just, for his kind permission to show these. (hopefully I will get to post a few more soon).
Locality: | South Crofty Mine, Northern Branch lode, Pool, Camborne - Redruth - Saint Day District, Cornwall, England / United Kingdom | |
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Notice the small 'pods' of dark Wolframite just above the scheelite occurrence |
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Locality: | South Crofty Mine, Northern Branch lode, Pool, Camborne - Redruth - Saint Day District, Cornwall, England / United Kingdom | |
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Dimensions: | scheelite approx 12cm pod, right of centre - lots of wolframite alongside |
Description: |
Scheelite is the buff-coloured material |
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Locality: | South Crofty Mine, Valley shaft, Pool, Camborne - Redruth - Saint Day District, Cornwall, England / United Kingdom | |
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markbeckett
Joined: 06 Oct 2016
Posts: 41
Location: Cornwall
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Posted: May 20, 2017 13:30 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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(in reference to the above mine shots, 'Northern Branch' TNL' is a piece of Tincroft North Lode - it leaves the main part of the lode just above the 175 fathom level - appearing again in the crosscut to New Cook's Shaft.'). Thanks
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markbeckett
Joined: 06 Oct 2016
Posts: 41
Location: Cornwall
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Posted: May 27, 2017 09:26 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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More photos of South Crofty Mine (mainly Tin), Pool,near Redruth, underground. Also taken in the early 1990s by Paul Oldfield -
There were historically over 30 different lode structures that the Mine had access to while in operation. Many of the 'lodes' are a product of 'brecciation versus cataclastic flow' occurring in discreet, fractured zones in the host rock that is either granitic (at depth) or meta-sedimentary (ie. 'in killas') in the shallower parts of the mine. Some of the lodes show more pervasive styles of mineralisation,where wall-rock is also mineralised and can also be associated with meta-basic intrusive rocks, known here as 'greenstones'. Paul's description is transcribed below,
''...in the crosscut north to New Cook's Shaft, Tincroft North Lode was split into three seperate sections, roughly 12metres apart. The footwall contained both arsenopyrite and chalcopyrite with very minor cassiterite and scheelite. As you will see this dips to the north at 45 degrees,whereas the next two are almost vertical. The next section contained sphalerite in bunches with sub-rounded clasts of greenstone wallrock, in quartz. This section was directly above the old ten-fathom level. The last to be encountered before reaching the Northern Branch, was solely chalcopyrite, with side-shoots of fluorite, which here was a bluish-green colour, and was massive. The strange thing was, these on exposure, turned a pale green and lost all of their bluish hue. In one of the photos you see there is a cavity in quartz, or what remains of the quartz. I had to strip the cavity before any further blast damage could occur...''
Locality: | South Crofty Mine, Northern Branch lode, Pool, Camborne - Redruth - Saint Day District, Cornwall, England / United Kingdom | |
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Dimensions: | the mine 'drives' are up to many metres in size |
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23671 Time(s) |
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Mineral: | Chalcopyrite in vein |
Locality: | South Crofty Mine, Northern Branch lode, Pool, Camborne - Redruth - Saint Day District, Cornwall, England / United Kingdom | |
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Dimensions: | fov is about 2.5metres |
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Mineral: | Fluorite |
Locality: | South Crofty Mine, Northern Branch lode, Pool, Camborne - Redruth - Saint Day District, Cornwall, England / United Kingdom | |
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Dimensions: | fov 20cm |
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Mineral: | Sphalerite |
Locality: | South Crofty Mine, Northern Branch lode, Pool, Camborne - Redruth - Saint Day District, Cornwall, England / United Kingdom | |
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Dimensions: | fov 2m |
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Mineral: | Sphalerite |
Locality: | South Crofty Mine, Northern Branch lode, Pool, Camborne - Redruth - Saint Day District, Cornwall, England / United Kingdom | |
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Dimensions: | fov approx. 1metre |
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23695 Time(s) |
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markbeckett
Joined: 06 Oct 2016
Posts: 41
Location: Cornwall
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Posted: May 27, 2017 10:07 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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Another South Crofty Mine photo, of an 'end' (of tunnel) that exposes a flat-laying 'magmatic sill' of granitic composition, (in the floor of the drive), that is intruded into the dark 'killas' around it. Flow-banding was recognised in its bulk texture. It occurred with tendril-like extensions or 'droppers' of finer-grained 'aplite' rock. The white spray painted lines were in preparation for the next blast. Photo by Paul Oldfield.
Mineral: | Granitic sill. |
Locality: | South Crofty Mine, Northern Branch lode, Pool, Camborne - Redruth - Saint Day District, Cornwall, England / United Kingdom | |
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Dimensions: | 3 or 4 metres |
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Other flat-lying magmatic structures at South Crofty are known as 'quartz floors' and were coarsely crystalline, with feldspar, wolframite and cassiterite. |
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markbeckett
Joined: 06 Oct 2016
Posts: 41
Location: Cornwall
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Posted: Jun 09, 2017 08:59 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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Here are some attractive specimens from Penlee Quarry, near Mousehole, Cornwall. The quarry has been worked for roadstone in the past but plays host to a complex exposure of metamorphosed 'greenstone' (metabasic intrusive), with some granite, associated with some highly altered 'killas' (meta-pelite). Mineralisation includes arsenopyrite, lollingite, pyrites, chalcopyrite, bismuth, topaz, molybdenite, chalcedony, siderite and scheelite with some wolframite and cassiterite with chlorite.
The following photos are of Chalcedony and Siderite, retrieved from a 'crosscourse' (ie. a vein emplaced in a different orientation to most other fractures). The last two pics are of the manual 'development' of the exposed crosscourse, from 'discovery to extraction' with hand tools.
Mineral: | Siderite on Quartz (variety chalcedony) |
Locality: | Penlee Quarry, Mousehole, Penzance Civil Parish, Cornwall, England / United Kingdom | |
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Dimensions: | 6x5 cm |
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Mineral: | Siderite on Quartz (variety chalcedony) |
Locality: | Penlee Quarry, Mousehole, Penzance Civil Parish, Cornwall, England / United Kingdom | |
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Dimensions: | 6x5 cm |
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Mineral: | Quartz (variety chalcedony) |
Locality: | Penlee Quarry, Mousehole, Penzance Civil Parish, Cornwall, England / United Kingdom | |
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Dimensions: | about hand-size |
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Mineral: | Quartz (variety chalcedony) |
Locality: | Penlee Quarry, Mousehole, Penzance Civil Parish, Cornwall, England / United Kingdom | |
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Mineral: | Quartz (variety chalcedony) |
Locality: | Penlee Quarry, Mousehole, Penzance Civil Parish, Cornwall, England / United Kingdom | |
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Dimensions: | 6x4.5cm |
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Mineral: | A 'crosscourse' vein |
Locality: | Penlee Quarry, Mousehole, Penzance Civil Parish, Cornwall, England / United Kingdom | |
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Dimensions: | a few metres width |
Description: |
photo by P. Oldfield, taken before an attempt to 'open it up'. |
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Mineral: | A 'crosscourse' vein |
Locality: | Penlee Quarry, Mousehole, Penzance Civil Parish, Cornwall, England / United Kingdom | |
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Dimensions: | a few metres |
Description: |
Photo by P. Oldfield - this was taken after initial development with hand-tools, a couple of months later. |
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23497 Time(s) |
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markbeckett
Joined: 06 Oct 2016
Posts: 41
Location: Cornwall
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Posted: Jun 11, 2017 08:55 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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This is a specimen that was retrieved from the ochreous/iron oxide filled 'pocket' within the South Crofty 'Tincroft North Lode', indicated in my earlier posting (I have repeated that photo as I thought it should be linked again here).
Mineral: | Quartz |
Locality: | South Crofty Mine, Northern Branch lode, Pool, Camborne - Redruth - Saint Day District, Cornwall, England / United Kingdom | |
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Dimensions: | a couple of metres |
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Check out the quartzy, ochreous pocket that was extracted just after the ealier blast, about centre-right in the image. |
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Mineral: | Quartz with Pyrite |
Locality: | South Crofty Mine, Northern Branch lode, Pool, Camborne - Redruth - Saint Day District, Cornwall, England / United Kingdom | |
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Dimensions: | about 11cm max size |
Description: |
Photo by P. Oldfield, from his collection. |
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Colin Fearon
Joined: 28 Oct 2020
Posts: 3
Location: Cornwall
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Posted: Oct 30, 2020 08:28 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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Hi Ian, I was just doing some on-line surfing when I came across your pic of the Botallack copper from the William's Collection.
I have a similar copper from Botallack which I purchased from Paul Lowe in Truro sometime in the nineties. Also from the Williams Collection but also with the number 112 affixed to it!. One of a pair or just a mis-numbering?
Regards
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ian jones
Joined: 29 Jul 2009
Posts: 112
Location: london
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Posted: Oct 30, 2020 08:52 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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That's interesting Colin. Will check the number of mine next time I manage to get home, probably in a couple of weeks, just in case it's incorrect.
Otherwise, I have no idea whether Col William's ever gave similar pairs of specimens the same number, but certainly not to my knowledge.
ian
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James Catmur
Site Admin
Joined: 14 Sep 2006
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Location: Cambridge
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Colin Fearon
Joined: 28 Oct 2020
Posts: 3
Location: Cornwall
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Posted: Oct 30, 2020 09:26 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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Hi James, yes we are. My specimen is slightly larger at 6" x 4" (150mm x 100mm)
and with much finer wires
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Jesse Fisher
Joined: 18 Mar 2009
Posts: 629
Location: San Francisco
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Posted: Aug 20, 2022 06:52 Post subject: Re: A mineralogical trip through the regions of the UK - England / Cornwall |
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A new/old bit from South Caradon.
Mineral: | Fluorite with Chalcopyrite |
Locality: | South Caradon, Liskeard, Cornwall, England / United Kingdom | |
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Dimensions: | 7x5x4 cm overall |
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7420 Time(s) |
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