Menu

List of news Items for 2023.  Scroll down for articles

  1. The Geology and Mining of Cligga Head (posted 1 Nov 2023)
  2. RGSC Rockstars! (posted 1 Nov 2023)
  3. RGSC Charitable Incorporated Organisation  (posted 30 October 2023)
  4. RGSC Charitable Incorporated Organisation (posted July 2023)

The Geology and Mining of Cligga Head - A Report by Jack Knight

The Royal Geological Society of Cornwall, RGSC, organised a field trip on Saturday 12th August 2023 to Cligga Head, St Agnes, Cornwall, UK.

The visit was all about the mining and minerals of Cligga Head and was led by Professor Frances Wall of the University of Exeter, Camborne School of Mines.

Professor Frances led us on an exploration of the St Agnes Area of Outstanding Natural Beauty to explain what minerals are present, the geology and formation of the igneous rocks in the area and how the landscape was mined.

Picture of Jack Knight on the left

 

Igneous Rocks and Greisens All rocks can be split into three categories: igneous, sedimentary and metamorphic. The rocks at Cligga Head are igneous, formed when molten magma intruded the Devonian clay slate country rock around 290 million years ago.

The magma cooled five kilometres below the ground and formed a small coarse granite batholith (nearly two kilometres squared). The granite contains quartz, feldspars and micas. The micas are so abundant it is called ‘muscovite granite’. 15 million years later, water heated to around 200 to 400°C that was carrying the elements boron and fluorine, entered the granite through fissures (cracks in the rock). The heated water dissolved the feldspar in the granite which reacted with the other minerals in the fluids to form wolframite and cassiterite. This process is called greisenisation and is what forms the distinctive veins at Cligga Head.  

Left photo shows the Greisen veins and the right photo a closer view

 

 

The Mining Industry of Cligga Head Wolframite contains the rare metal tungsten whereas cassiterite contains tin. Both metals are important for industry, hence the mining at Cligga Head.

The first location that Professor Frances took us to was the very windy remains of a 20th century building (left photo) and abandoned mineshaft (right photo). The building was an extraction and processing site for tungsten during the Second World War.

 

The wolframite (left photo) was mined from the Greisen and then crushed. The crushed dust was left to settle in the buddle tanks. This separated the heavy tungsten ore from the rest of the less dense minerals of the wolframite.

Sometimes this process may have to have been repeated multiple times to extract the tungsten ore, which was very expensive and time consuming.

The Cligga Head mine began decreasing production in 1944 when Britain started importing American tungsten, which was much cheaper than the tungsten produced at Cligga Head.

Eventually after the war ended Cligga mine closed with a grand total of around 300 tons of tungsten produced.

 

The Granite Cliffs The next location that Professor Frances took us to was a perfect viewpoint of the granite and the Greisen veins (photos left and right).

From where we stood we could see many adits in the cliff face demonstrating how vast the mine workings at Cligga were.

It also showed how the greisenisation had affected all the granite of the area around Cligga Head with the unique landscape and excellent veins resulting in it being designated a Site of Special Scientific

 

The Elvan Dyke The final location that Professor Frances took us to was a small quarry. Here a dyke had intruded the metasediments of the surrounding country rock. The dyke comprises a fine grained rock called quartz porphyry, which has a composition much like granite.

Elvan is a Cornish word that means a rock that is very good for building material. In contrast to Cligga Head, which had been mined for minerals, this dyke had been quarried for building stone. On breaking an elvan specimen with a piece of rock as a hammer we were able to see the fine grained quartz crystals. These quartz crystals make up the majority of the minerals in the elvan dyke.

After seeing the fine grained elvan, Professor Frances asked us to examine the margin between the dyke and the rock above it (right photo). The rock had some joints and looked like the same slaty rock that made up the rest of the country rock. Then Professor Frances asked us whether the rock had been baked when the dyke intruded or was deposited there after the dyke had cooled and been eroded. On closer examination of the margin I believed it had been baked as the dyke appeared to have finer grains next to the boundary. This implied that when it had intruded, the outer edge of the dyke had cooled quicker on the colder country rock forming a chilled margin in the dyke and a baked margin on the country rock. 

Conclusion I would like to thank Professor Frances Wall for leading this fascinating field trip and the Royal Geological Society of Cornwall for arranging and organising the event. I learned so much I never knew about minerals and mining during this trip and it showed me how much there is to discover in the ever-growing field of geology. I highly suggest that you join your local geological society for the engaging and eye-opening content from field trips and talks. 

  

RGSC Rockstars!   RGSC members, Jack and Tom Knight have both won first prize in this year’s Rockwatch Rockstars competition. They received their prizes from Rockwatch Chair, Claire Byrne, in London on 27 October 2023.

Jack won 1st Prize in the Rockstar Young Writer (16-18 years) category for his report 'The Geology and Mining of Cligga Head' after attending the RGSC fieldtrip to Cligga on 12 August.  A summary of Jack’s write up is reproduced on the RGSC news page as a report of the fieldtrip. Tom, meanwhile won 1st Prize in the Rockstar 13-16 years category with a report about 'The Geology of Bude's Breakwater', which is near to where the family live in north Cornwall. 

Jack said, ‘I was thrilled to receive the prize. Geology is such a major part of my life and I am always inspired by the RGSC events. Thank you to everyone who enabled me to have this wonderful opportunity.’  Tom said, ‘I feel honoured to win first prize. I really appreciate Rockwatch for hosting this. The competition is always such fun to enter and the prizegiving was a fantastic day.’  Tess, their Mum, said, ‘We’ve been members of Rockwatch for years. It has been wonderful to see the boys develop their fascination with geology.’

RGSC President, Professor Frances Wall said, ‘Many Congratulations to Tom and Jack. We always enjoy seeing Tom, Jack and Tess on RGSC fieldtrips and it is brilliant to see such success.’

Rockwatch is the UK's nationwide geology club for children. It introduces children and young people to the amazing world of geology, by running events ranging from field trips, residential trips, to museum events and more, publishing a glossy magazine, and running competitions. https://www.rockwatch.org.uk/.

The Royal Geological Society of Cornwall organises fieldtrips for members and guests to enjoy the geology and scenery of SW England and learn about the awe inspiring stories of  deep geological time. The age of fieldtrip attendees during this year has ranged from about 10 to 80! 

Update - RGSC Charitable Incorporated Organisation – October 2023

Our last update was in July (below) when we announced that our application to become a CIO had been accepted by the Charity Commission and that we had transferred our bank balance to our new Co-operative Bank account.

We are now very pleased to say that the final step was completed on 18th October 2023, with the Charity Commission approving the Vesting Deed, which transferred all the assets from ‘old’ RGSC to the new CIO and so the merger of the two charities. As explained in July, the CIO trustees (Hilary Mitchell, Frances Wall (members of the ‘old’ RGSC Council) and Stephanie Clemens, Gareth Parry, Kathryn Moore (Independent Trustees) will now appoint as trustees, the members of ‘old’ RGSC Council who were not already trustees of the CIO: Loveday Jenkin (Vice President), Linda Beskeen (Secretary), Nick Farrell (Treasurer), Beatrice Kerno (Membership Secretary) and Caradoc Peters (Council member). Gareth will then stand down as a trustee but we are delighted that Stephanie and Kathryn will stay on the RGSC Council.

To confirm, the new RGSC CIO Council will then be:

President: Professor Frances Wall

Vice President: Dr Loveday Jenkin,

Secretary: Linda Beskeen

Treasurer: Nick Farrell

Membership Secretary: Beatrice Kerno

Ordinary Members of Council: Stephanie Clemens, Hilary Mitchell, Dr Kathryn Moore, Dr Caradoc Peters 

RGSC Charitable Incorporated Organisation update - July 2023

Since we passed the resolution in February at the AGM for RGSC to become a CIO, we’ve made great progress. Our CIO application was accepted by the Charity Commission and the Royal Geological Society of Cornwall came into existence as a CIO on 2nd May 2023 with a new charity number, 1202892.

A new bank account for the RGSC CIO has been opened with the Co-op Bank and we have transferred our balance from the old HSBC account to this new account. The Co-op account provides internet banking and is free which is a big advantage over HSBC where we don’t have internet banking and HSBC also charge us just for holding the account. Although Co-op Bank no longer has any branches open in Cornwall, they have an arrangement with Post Office Counters so that customer transactions can be made in any convenient post office.

Now that the bank balance has been transferred, we will send the Charity Commission the Vesting Deed. This is the legal document that transfers all the assets from the ‘old’ unincorporated RGSC into the new RGSC CIO. Once this has been accepted by the Charity Commission, the two ‘versions’ of RGSC are then officially merged and the ‘old’ charity will cease to exist. The new charity number and CIO constitution will then appear on our website.

HSBC will arrange for standing orders to be transferred to the new Co-op account, so don’t be alarmed if you see this change in your banking information. Please remember to use the new bank details – below for all future payments.

New bank details for all future payments:

Account name: Royal Geological Society of Cornwall

Bank: Co-operative Bank

Sort Code: 08-92-99

Account number: 67294781

The final step is to appoint the current members of the Council as CIO trustees. At the moment the CIO has five trustees; Frances Wall (current RGSC President) and Hilary Mitchell (current Council member) plus three independent trustees (Gareth Parry, Stephanie Clemens, Kathryn Moore) who were appointed to make sure the transfer was done fairly. The current CIO trustees have the power to appoint new trustees once the ‘old’ RGSC has been merged with the CIO and no longer exists as a separate charity. The current Council members who will join the CIO are Loveday Jenkin (Vice President), Linda Beskeen (Secretary), Nick Farrell (Treasurer), Beatrice Kerno (Membership Secretary), Caradoc Peters (Council Member).

On behalf of all of us, I would like to thank Hilary Mitchell for all her sterling work and attention to detail to steward through an important change to the governance of the Society that will stand us in good stead for the future. Counterculture solicitors have been guiding us safely through the process.

Frances Wall, President RGSC