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Mining in Cornwall (The St. Erth Valley mines)


A lifetime could be spent in the study of Cornish mining and still know only a fraction of it’s history.  It follows that this short introduction, can only give a flavour of the subject, but it is hoped that it will help in the understanding and enjoyment of the many industrial remains to be seen.


Cornwall is famous for its long history of mining Tin, but other important minerals such as: - Copper, Lead, Zinc, Silver, Arsenic and Uranium have been “won”.   From our history lessons at school, we remember the “Bronze Age”, but as bronze is an alloy of Copper and Tin, and as Cornwall was one of the few places in Europe where Tin was to be found, then it’s importance in mankind’s history, is evident.

Origins of the minerals


The valuable minerals that have been worked in Cornwall had their origins in the molten core of our planet.

There were occasions in geological time, when the molten material from within, pushed up through the surface rocks, to form features such as, Dartmoor, The Penwith Peninsular and smaller examples like Carn Brea hill and Godolphin and Tegonning hills.  The molten granitic material was often accompanied by other valuable molten minerals that did not dissolve in the granite and so ascended around the granite.   As the surface rocks were pushed up by the molten granite, they were baked and cracked.  The molten minerals found that these cracks were an easier route and travelled up them until they cooled to such an extent that the minerals became solid.  As different minerals have different melting (and freezing) temperatures, then the different minerals would become solid at different depths in the earth.

The important thing to remember, is that whereas coal was produced by plants and trees rotting and being buried and compacted with time into a Horizontal seam , the minerals, in Cornwall, that come from the core of our planet, come up nearly vertically and mostly in much thinner deposits than coal.

Where the minerals came up to surface, then erosion over millions of years, broke up the rocks into a gravel and released the minerals from the rocks surrounding them.

Where tin had travelled to the surface in a crack in the surface rocks (a “Lode” ) and had been eroded and released by the weather into grains of Tin Oxide (Cassiterite), it was washed by rains into streams.  The cassiterite is a very heavy mineral and so it was inclined to sink into the bed of the stream, rather than be washed away like the lighter rocks and mud.


Early mining and “The Golden Fleece”


The early “Tinners” dug down in what had been stream beds until they found the cassiterite, but this was mixed with other gravel.  To separate it, they washed the gravel in fast flowing streams.  The lighter minerals would be washed downstream a good distance, whilst the cassiterite being heavy, would sink rapidly to the stream bottom.

In order to recover the cassiterite, a fleece from a sheep, or a grass turf, would be placed on the bed of the stream where it was predicted that the cassiterite would come to rest.  The cassiterite would become enmeshed in the pile of the fleece or turf and thus impeded from being washed further downstream.  When the fleece or turf was full of cassiterite, it was removed from the stream, dried and then burnt in a charcoal fired furnace until the fleece or turf was destroyed, leaving the tin metal to be run off into ingot moulds.  This same method was used for the separation of alluvial (eroded gravel) gold in ancient times and is the origin of the fable of the Golden Fleece.

The tinners perfected the art of carrying out quick trials of the gravel deposits to discover the amount of cassiterite in it.  They would put a small quantity of gravel into a shovel with a little water and swirl the shovel around with a special motion that caused the heavier particles of cassiterite to be deposited at a different position on the shovel to the lighter and valueless gravels.  This process is called “Vanning” in Cornwall and the similarity between this and the later American term of “Panning” for gold is evident.  In fact the methods used by the early American prospectors who were searching for the easily won gold bearing alluvial gravels were almost identical to the methods used by the Cornish tinners centuries before.







Early Lode Mining


After several centuries, almost all the workable deposits of alluvial cassiterite had been exhausted but the miners knew where the cassiterite had come from.  Where the lode came to surface, it was often partially weathered and softened.  The miners would dig out the softer parts and process them as before.  One perpetual problem was that when you dig a hole deep enough, it fills with water!    The simplest way of starting to recover the cassiterite from the actual lodes was to look where the lodes were evident in the cliffs at places like St Just.

The next step was to tunnel in to the lode in the cliff face, at a height just above high tide mark.  The tunnel (drive)

would be arranged to progress slightly uphill so that any water percolating into it, would run downhill and out of the tunnel.  As the lodes are nominally vertical, then the miners were able to excavate upwards and remove the lode above them up to near surface. A further problem was that the tin oxide won by lode mining was encased in a host rock. The miners therefore had to crush the lode material until it was fine gravel before they could separate the cassiterite from the waste materials.  This early principle for the mining of lodes was also applied to valleys, where a drive was started from the bottom of a valley into a hillside where a lode had been exposed and then the lode worked in the hill above the drainage drive (adit) level.  This method of mining was practised in the St Erth valley in the early stages of lode mining history.


Early Tin Smelting                   


To convert tin oxide (cassiterite) into tin metal, the early method was to use a charcoal furnace with large bellows.  This was called a “Blowing House” and several places of this name are to be found around Cornwall where these early smelters once existed.  Charcoal was used as it is free of impurities and was readily available, there being no coal in Cornwall.  In early times, there had been significant forests in Cornwall, but these were soon decimated in the pursuit of charcoal and the resultant soil erosion has ensured that these forests can not be recreated.

Soon the local haulage industry was in action importing charcoal from Devon.  The Cornish roads were mud tracks, which were not maintained and were very difficult for wheeled vehicles in summer and virtually impassable in winter.  The method was to use teams of pack mules of up to 100 animals for almost all transport.  In later periods, the mules were imported from northern France, where the largest female horses were mated with the sturdiest male donkeys.  The horses were put into a partial pit and blindfolded!


Deep lode mining


Having exhausted the alluvial tin and then the lode tin above water level, the miners looked at the tin lodes that went down below the water level.  These lodes could be worked if only the water that soon filled any excavation could be removed.  The first methods were to sink a shaft rather like sinking a traditional well.  A windless was erected over the shaft and a bucket was employed to raise the excavated material and the accumulated water.

 This method was good only for shallow workings, so further power was needed.  Next a large windless machine operated by horses was erected near the shaft and a rope passed over a headgear erected over the shaft and down the shaft where it supported a larger bucket called a kibble.  The weight of the rope itself becomes very significant when the shafts become deeper.  

 Where there was water power available, then waterwheels were employed to drive pumps and ore crushing machines, but when these available methods had reached their limit, there was an urgent need for a more powerful method of driving the machinery.  The truly great inventor Thomas Newcomen devised a machine, which used fire to produce steam, the condensing of which, in an enclosed cylinder, fitted with a movable piston, could produce greater power.  Newcomen’s genius lay especially in that he devised a machine that could be produced using the existing crude manufacturing technology and yet still be reliable and functional.  By contrast James Watt’s later proposed improvements to the Newcomen engine were impractical and unworkable, until the great ironmaster John Wilkinson invented a special machine tool that would bore a large cast iron cylinder to the accuracy required to allow the potential of the proposed Watt improvements to be achieved.  Further significant developments to the steam engine and the pumping apparatus by Cornish engineers such as Trevithick and Wolf resulted in the evolution of a highly powerful and efficient machine that was in the very forefront of world technology in its day.  As an indication of the development, the efficiency figures  (Duty measured as millions of pounds of water raised thru one foot by one bushel of coal) were:-  Newcomen engine  7 units,   Watt engine  15 units  Final Cornish design  65 – 85 units.  These later world-renowned machines enabled mines to be worked up to 3000 ft deep.

 To remove the lode material initially required men to beat chisels with hammers for many hours to achieve a small result, because of this tunnels were as small as possible and men had to be able to use the tools with both right and left hand equally well.  Later gunpowder was introduced and holes are drilled into the rock and charged with explosive and fired.  Hole boring was made easier with the introduction of boring machines but the early versions made so much dust that they were referred to as “Widow makers”

Industrial Development.

As the mines became deeper, they needed to utilise more powerful and expensive machinery both for the excavation of the ore and the separation of the cassiterite from the waste rock at surface.  It became necessary for many small mines to combine into groups so as to share the expense and to benefit from economies of scale.

The need for greater financial input exceeded the ability of the local investors to support, so it became more usual for shares to be floated and traded on the London markets.

Large engineering factories were established to produce the engines for pumping, winding, crushing ore, rock drills, water wheels.  Other concerns manufactured explosives, fuses, ropes, candles and smelted ore into metal.

A much greater volume of goods had to be transported.  The steam engines vast appetite for coal had to be supplied from South Wales by a fleet of small sailing vessels.   Instead of having to unload on beaches, new harbours, such as Newquay, Hayle and Portreath were constructed by consortiums of local businessmen. The North coast of Cornwall was most hazardous to navigate in the winter months, so supplies had to be stockpiled on the docksides in winter until the weather improved in the spring.

The difficulty of transport on land, led to the establishment of very early horse drawn railways to the major mines from Portreath, whilst the Cornish engineer Richard Trevithick made and demonstrated viable road and rail steam locomotives many years before Stevenson etc.  It seems difficult to accept nowadays, that Cornwall’s mining areas were once the most technologically advanced and highly industrialised places on earth.


The St Erth Valley.


Today’s valley is a haven of peace and tranquillity.  In the past it was alive with activity. There were medium sized mines along the valley and several large concerns just to the East of Relubbus Bridge.  To the South was a run of mines From “Penburthy Crofts” on Long Lane running through to the mines of Marazion marshes.

The riverside track was the local M1.  It was the main supply lifeline from the docks at Hayle carrying in coal, rope, explosives, timber and the many day to day mining requirements.  The 100 strong pack mule trains, returned with tin ore for smelting in Cornwall and large volumes of Copper ore, from the mines East of Relubbus Bridge, which needed to be shipped to South Wales for smelting.

East of Relubbus Bridge were extensive water wheel driven banks of large mechanical hammers called “Stamps”.

These pulverised the ore rock into gravel so that further very extensive washing processes could separate the valuable minerals.  The din of these stamps could be heard for several miles and continued day and night, unless there was a drought!  From the system of water canals (“leats”) a supply was taken that passes under the main road near Relubbus Chapel and finally entering the “Penburthy Crofts” mine via a tunnel (“Drive”) that fed the water to a 34 ft and a 36 ft waterwheel situated underground in excavated caverns.  These wheels worked pumps to help remove water from the mine.  It was much cheaper to utilise waterpower where possible, rather than incur the great expense of a steam pumping engine and its appetite for coal.

From examination of the 2500 Series County series Ordnance Survey map of 1876, You will notice a leat taken from the Hayle River to feed further Batteries of stamps at Carbis Mill.  There were more stamps near St Erth Bridge, where the lane is still called “Battery Lane”.

The known mineral lodes of “Ennys Wheal Virgin” which ground the “River Valley Caravan Site” now occupies, cross beneath the Hayle river and were worked there by the Gurlyn mine previously worked as “Wheal Fox”

 In their later working they were both operated by John Taylor and Sons who were renowned mine managers.

The workings join under the Hayle River in one place.

 When you pass down the lane towards Relubbus Bridge, look out for the roughly rectangular area shown as 1174 on the map.  This is a relic of another industry, that of growing reeds for thatching.  This plot is almost always covered with water, like a rice “Paddy Field”.   The reeds still grow here every year, but nobody comes to harvest them any more!

Further down the lane, the cottage on the left was part of mine buildings, most long since demolished.  A mine tunnel still exists in the garden entering the hillside to the north.  This continued at least half a mile on the course of a mineralised lode called an “Elvan Dyke” and later was utilised to unwater  “Wheal Susan” and Bosence mines near Townsend.  Drainage water from “Wheal Fancy” situated in the field opposite the cottage, used to be carried over the Hayle River in wooden canals called “Launders” and used to drive waterwheels in what is now the cottage garden, but was once, a small ore dressing plant.

   It is estimated that in excess of a thousand persons worked within a mile of Relubbus Bridge, the miners having a life expectancy of less than 40 years on average.  Women and children from the age of six years were employed in the ore processing work at surface without shelter in all weathers.

For those who wish to learn more, many books on Cornish Industrial History are available, also there are societies

Such as: -  “The Carn Brea Mining Society” Who specialise in mining history and exploration.  (01209 212149)    web                                   

And “The Trevithick Society” who specialise in Cornish Industrial Archaeology including mines.(01209 716811) web

Also see King Edward Mine  Web © 2003

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