Jolyon's Travels - Part 3 - Devon and Cornwall

Not content with simply driving all the way up to Scotland, across to the other side of Scotland, back again and back down to London, I thought it would be fun to go down to Cornwall for a few days.

I figured it would be better to go all the way to the far west (the St Just area) and work our way back, so after an early start and lots of driving, we ended up around lunchtime at the famous Botallack mine. Anyone who's ever seen any books on Cornish mining, or even postcards from Cornwall will recognise this view - the most famous Cornish mining scene, of the Crown's Shaft engine houses of Botallack mine. I first collected at this mine when I was around 7 or 8 years old, and it was great to be back.

Crown's Shaft engine houses at Botallack

Mining at Botallack is very ancient. Noone really knows exactly how far it dates back, but best estimates are that mining goes back to at least 330BC (with stream working for alluvial tin and possibly underground workings). And mining continued in the region until the 1980s when the nearby did exploratory work to determine the fesability of re-opening the Botallack mine as an extension of their workings. The modern head-frame seen below at Allen's Shaft was built during this period. Unfortunately the crash in the price of tin in 1985 killed off this idea, and in 1990 the Geevor Mine itself finally closed.

Allen's Shaft at Botallack

Here's a great view of the collapsed and overgrown arsenic workings at Botallack. The Arsenic "Labyrinth" was built in the first years of the 20th century to remove arsenic from the ore before processing. Arsenic contamination was a frequent problem with tin ores in Cornwall (due to relatively high levels of arsenopyrite) and this processing of the ore in a controlled system resolved the terrible arsenic pollution problems from smelting the ore, and also ended up with arsenic oxide poweder, which was a valuable commodity in it's own right. Cornwall exported thousands of tonnes of arsenic to the USA in the late 19th and early 20th century (it was needed to combat the Colorado Beetle and Boll Weevil infestations).

The Arsenic Labyrinth.

In the background of the photo below you can see the engine house at West Wheal Owles which was our next stop, just a short walk south from Botallack mine.

The landscape of Cornwall, and in particular this area on the western coast, is dotted with old mine workings, and in particular the engine houses, mostly in various states of ruin, The engine house at West Wheal Owles is good example of the state of preservation of many of these ruined engine houses.

West Wheal Owles mine at Botallack

Here's a view up from inside the ruined engine house.

View inside the engine house

As you can see in the first photo of West Wheal Owles there is a large mine dump right next to the mine building (actually the landscape is covered with mine tips, many overgrown - the tip here just happens to be reasonably well exposed) - so we started exploring the minerals on the dump.

Hunting for minerals on the West Wheal Owles dumps

Originally I had suggested we walk on straight to Wheal Edward, which is a short walk further to the south, because on previous trips I had remembered never finding anything of interest in the dumps at West Owles, but we could see flashes of blues and greens even from the path, so we decided to give the mine a proper examination. It proved very successful. Minerals we believe we found on this tip (none have been included quartz (including amethyst), connellite, botallackite, hematite (specularite, nice crystals, on quartz) and siderite.

Here's a sample I picked up - specular hematite crystals on quartz.

Specular Hematite on Quartz

Our next stop involved a very quick drive along the coast "road" (more of a track than a road). We parked up by the extensive clifftop dumps at Wheal Cock, which is a very short distance north of Botallack (and interconnected underground).

The dumps at Wheal Cock

This is another site I have collected at since my childhood, and the site seems the same now as it always has. Generations of collectors have visited these dumps, but due to their extensive size there's still something to be found every trip. And even if you find nothing, the views are of course spectacular. There are no engine houses left standing at Wheal Cock, but the capped shafts remain.

Capped shaft at Wheal Cock

It was relatively easy to find representative specimens on the dumps at Wheal Cock - here's are some examples of what we found. The coin used for scale (British 2 pence) is about 26mm wide, or almost exactly one inch.

Vein of amethystine quartz

Chalcopyrite crystals in quartz vein

Selection of copper secondary minerals (possibly botallackite and connellite

We left the St Just area and drove back east. Our next stop was another coastal mining area, but on the northern coast - the famous Cligga Head area. The first photo here shows some of the overgrown mine dumps, which were beautifully in bloom with heather and wild flowers while we visited. In the distance is the cornish coastal resort town of Perranporth with its wide sandy beaches.

Cligga Head in bloom

Unlike most of the mines in Cornwall that were tin and copper mines, the Cligga mine mined tungsten as well as tin, and was one of the major sources of tungsten in the UK. It finally closed in early 1945, just before the end of the second world war.

One of the classic sites that any geology student in Cornwall is taken to is the greisen stockworks.



The greisen is a sheeted vein system formed from parallel quartz/tourmaline veins cutting the granite. The granite between the veins has since been extensively kaolinized (the feldspar has broken down into kaolinite clay).



Collecting at the greisen veins is not allowed (it's a SSSI - site of special scientific interest - and protected by law), so we restricted our collecting there to reflected photons entering our digital cameras. However, the best collecting is to be had in the mine dumps (where collecting is allowed), and we spent the remainder of the afternoon digging through these. There was plenty of cassiterite to be found, in crystals up to 1cm on matrix (although larger crystals did tend to be damaged), and we got some good samples of bladed wolframite, along with various copper secondary minerals that need further analysis - but langite is a possibility.

We made our way to our accommodation for the night, and planned our second day. Our first stop would be the Royal Cornwall Museum, in Truro. The Rashleigh Gallery at the museum holds one of the best public displays of Cornish minerals. Here's a photo of the gallery, which isn't large but is full of fantastic minerals.



Philip Rashleigh (1729-1811), after whom the gallery is named, built an extensive collection of Cornish minerals during the height of the Cornish mining boom, and is well-known to collectors for the book he published in 1797, Specimens of British Minerals, Selected from the Cabinet of Philip Rashleigh. Several of the specimens published in this book are now on display in the collection. Here's an example, an engraving from the 1797 book of chalcocite from Cook's Kitchen mine, near Redruth.



Described, by Rashleigh, as:



And here is the same specimen as it is today in the museum collection:



My favourite display in the collection was this cabinet of Cornish liroconite and other copper arsenate minerals.



Not least because of the mineral in the center, which is quite possibly my favourite mineral specimen of all time - the world's largest known crystal of liroconite, 3.5cm wide. This crystal is from the famed Wheal Gorland mine in Gwennap, near St Day.



Here's another classic Cornish mineral, a wood tin (a variety of cassiterite) from Wheal Kitty, near St Agnes on the northern coast (just a few miles west of where we were at Cligga).



And something a little more unusual - a botryoidal sphalerite from Wheal Unity in Gwennap, near St Day.

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I don't have room in this report to show all the photos I took, but click on the following links to see a large slab of rhodonite from the Week Mine in Devon, a nice bournonite from Herodsfoot Mine, a vial containing manaccanite (a variety of ilmenite) and an interesting tetrahedrite from near Wadebridge.

Our final excursion for the short trip was to visit another tungsten/tin mine - this time in Devon, the Hemerdon Mine. This mine is now owned by Australian company Wolf Minerals, who are planning to reopen the mine as a massive opencast tungsten mine. The mine has significant tungsten reserves and once operational it will be one of the world's largest tungsten producers. We obtained permission from the company's UK representatives for the visit and went for a short visit.



Hemerdon is famed for its scorodite, and fans of British minerals will remember that this mine has been worked commercially for scorodite specimens sporadically over the last 9 years with some exceptional specimens coming to market. Although we did not find any scorodite of that quality, we found small crystalline areas of scorodite, good cassiterite, plenty of very nice wolframite and, on further examination of specimens on my return, yellow balls of russellite on cassiterite.

Here's a photo of one of the wolframites that we found.



After a nice meal with friends that evening, we drove back to London the following day, stopping for one last excursion, to visit a famous (but non-geological) formation of rocks in Wiltshire. We didn't pay the extortionate entrance fees and instead took photos from outside, but they came out pretty well...



The very next day we got up early, went to Heathrow and flew to Russia where the adventure continued, but for that you'll have to wait for my next report...

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