The Mining Trails are a 60km network of walking, horse riding and cycling trails opened in 2010. The routes are largely based on the trackbeds of tramways and railways that were used to transport ore from the mines to the ports on both coasts. For this reason, the project was originally known as the Mineral Tramways.
In the early 1820s, a young man called John Taylor obtained the lease on abandoned mines in the Gwennap parish, and after re-working some of the old deposits, discovered what was at the time the richest copper deposit in the world. Initially, the ore was shipped from Portreath but the transportation fees started to grow as news of John Taylor's good fortune spread. This greed backfired, as in 1824, John Taylor built his own tramway through the Carnon Valley to Devoran, and Devoran began to take over from Portreath for servicing the mines in the Redruth and Camborne area.
The Redruth and Chasewater Railway was an early industrial line which evolved from John Taylor's tramway and eventually served many of the mines in the Camborne-Redruth area. The line ran to Devoran and Point Quay on Restronguet Creek and initially used horse traction. Later, steam locomotives were used but these terminated at Devoran. For shunting at Devoran and for the extension to Point Quay, trains were still hauled by horses. It was a single railway line all the way from Redruth with passing places. If two trains met between passing places, the drivers drew lots to determine who had to reverse.
A tailings dam is used to store the mineral waste that remains after separating the ore from the waste rock. Typically the tailings take the form of dust and grit which is piped in as a slurry mixed with water. Over the lifetime of the mine, as more waste is produced, the dam is added to deepen the lagoon and additional lagoons may also be appended. The dams themselves are often constructed from coarser mine waste.
The valley below Wheal Maid was used as in the 1970s and 1980s a tailings dam (waste dump) for the Mount Wellington tin mine. The mining company who owned the Wheal Maid site sold it to Gwennap Parish Council for £1 in 2002.
The mine waste used to create the dams, and the tailings (grit and sludge) within the lagoons all contain residual minerals. Of these, the grey sand in the lagoons with yellow mineral crystals has the greatest potential to release minerals into the water. As a result, the lagoon water contains high levels of arsenic with the water in the lower lagoon containing the highest levels.
Note that walking past the lagoon doesn't pose a serious health risk because these materials are not volatile and do not evaporate into the air - they stay in the lagoon. The main risk to the environment is from water escaping from the lagoon.
Motorcycles are illegal on the land for a very good reason: a lagoon of toxic waste ranks high in the worst places imaginable for a sport that involves large amounts of soil disturbance, with the potential to expose not only motorcyclists but also passing children and dogs (both with lower tolerance levels than adults) to airborne dust or mud spatter containing high levels of arsenic. Any incidents should be reported to the police (101).
Taylor's engine house was constructed in 1826 and is one of largest and oldest surviving pumping engine houses in Cornwall. Unfortunately, expansion of the shaft throat has caused some serious structural damage. It has a large detached stack but all that remains of the boiler house on the side of the engine house is humped, disturbed ground extending to the rear.
There are records of Wheal Maid (also known as Wheal Maiden) being worked in the 1770s and by 1780 it had been amalgamated into the Great Consolidated Mines. It is shown on a map from 1819 stretching to a depth of 130 fathoms below the drainage adit and profits from 1800-1840 are said to have reached £200,000 which is equivalent to around £20 million today. The mine was still producing copper and tin in 1865 as part of St Day United Mines but was making a loss by this point. Some exploratory mining was done in the mid-1980s of the interconnecting network of mines in the area which also involved connecting these to Wheal Jane.
A number of mines neighbouring Wheal Maid including Wheal Girl, Wheal Virgin and Wheal Fortune were all interconnected underground. Seven pumping engines were being run flat-out to drain them but despite this, they were still struggling to keep water levels down. The engines were so expensive to run that all the mines closed in 1779.
In 1782, after the mines were amalgamated, five newer, more efficient engines were purchased to pump out the water saving £11,000 per year (equivalent to around a million pounds today) on coal compared to the previous seven.
Deep in the earth's crust where there is lots of sulphur and little oxygen (hence the smelly sulphur compounds around volcanic vents), copper occurs as crystals of sulphide compounds. Nearer the surface, chemical reactions with air and water form brick-red oxide and blue-green carbonate compounds and also copper sulphate. The latter is the blue stuff from school science lessons which you may vaguely recall is soluble in water; thus it became concentrated at the water table. In the Ice Ages that followed, Cornwall was scoured by glaciers which bulldozed away many of these concentrated deposits. Early copper mining took place on the few remaining areas of these surface layers, but it was not until innovations in pumping technology that copper mining could be carried out on the deeper sulphide deposits and these account for the bulk of the ore mined. The most common ore (called chalcopyrite) is a copper-bearing version of "fool's gold"; when pure it looks like gold but where it meets air and water, patches of iridescent green, blue and purple form and so it was known as "peacock copper".
Public byways are rights of way down which motor vehicles may be driven depending on how brave you are and how expensive your car is to fix. You are also permitted to use a horse-drawn carriage, should you own one. Byways tend to be surfaced in an ad-hoc manner either with gravel or occasionally with a smattering of tarmac, but still leaving plenty of room for a good crop of grass to grow down the centre. They are conventionally marked using red waymarks or a "Public Byway" sign. There are 130 miles of byways in Cornwall.
Mining at Poldice (pronounced to rhyme with "spice") was initially for tin. A document from 1512 about a theft of tin "near Poldyth in Wennap" indicates that mining was probably taking place at that point. In the 1690s, Poldice was described as "that unparalleled and inexhaustible tin work…which for about forty years space hath employed yearly from eight hundred to a thousand men and boys."
By 1788, the output of copper ore exceeded that of tin, and by the 1790s it was making a good profit. In the early 19th Century, it was merged with Wheal Unity.
Like many others in the area, the mine was very wet and in 1842 the pumping engine was raising an average of 887 gallons per minute. In the 1860s, mineral prices dropped when large reserves were found in Spain and in the 1870s Poldice became uneconomical due to the cost of pumping water out of the shafts. The engine houses and most of the structures associated with this period of mining are gone. Most of the remains visible today are from a period of re-working for arsenic from the end of the 19th Century until 1929.
The isolated chimney stack and remains of a labyrinth above the main mine buildings are from an arsenic works built initially in the late 19th Century which continued to be used into the early 20th Century.
In America, during the 1870s, Colorado beetle was devastating cash crops including cotton, tobacco and staples such as potato. At the time, the most popular pesticides were arsenic compounds so this led to a sudden increase in demand for arsenic. Since this was soon after the collapse in copper prices, this delayed the closure of many mines and during this period, over half of the world’s supply of arsenic was produced from mines in Cornwall and Devon.
Arsenic had a variety of chemical uses including metal alloys, clarifying glass and in pigments. In Victorian times, an arsenic-based pigment known as "Scheele's Green" (copper arsenate) was used to colour sweets green. Later, the same compound was used as an insecticide!
Arsenic pigments were also popular in Victorian wallpaper manufacture to create green and yellow print. Unfortunately in the Industrial Revolution smogs, these arsenic compounds reacted with the acidic coal fumes to form lethal arsine gas which is even more toxic than arsenic itself.
The concrete stump beside the junction is one of the foundations for an aerial ropeway supported on steel pylons. Tin and tungsten ore were mined at Park-an-Chy mine about a mile away but this did not have an adequate water supply to process the ore, so it was transported on the ropeway to Poldice for processing.
In order to be processed, ore-bearing rock mined from mineral veins needed to be crushed to a powder. In earlier times, millstones were used to grind down lumps of ore but later it was done using a process known as "stamping" where the ore was crushed by dropping heavy granite or metal weights to pound it against another hard surface (often a piece of granite known as a mortar stone - as in "pestle and mortar"). The crushing was automated first with waterwheels and later with steam engines. The process was far from quiet and could often be heard from a number of miles away.
The three concrete structures on the way down the hill are the bases of Californian stamps and date from the late 1920s.
Californian stamps were developed in America during the gold rush and had a number of design improvements over the Cornish stamps from which they were derived. Rather than using square stamping heads, the Californian ones were round and the mechanism was designed to rotate them as they were lifted so that the wear on the head was evened-out. Californian stamps were also more rapid and could crush 50% more ore in the same amount of time as the traditional design and this led to their use in Cornwall too.
The barren areas of the Poldice Valley are known as "The Sands" and contain arsenic which inhibits the growth of most plants.
Arsenic disrupts the production of the ATP (energy carrying) molecules vital in the metabolism of multi-cell organisms (in plants as well as animals). Due to its toxicity, arsenic was used as an insecticide and rat poison, and by the ruling class to murder one another. As the toxicity extends to plants, highly contaminated ground often has limited or stunted vegetation.
An adit is a roughly horizontal tunnel going into a mine. In Cornwall these were important for drainage as many of the ore-bearing veins are close to vertical, through which water can easily seep. Drainage adits were sloped slightly upwards to meet the main shaft, so water trickling into the main shaft from above could be diverted out of the adit. Below the adit, engines powered by waterwheels or steam were needed to pump the water up to the level of the adit where it could then drain away.
During the 1730s, the water-powered engines at Poldice Mine were unable to pump the deeper levels dry. In 1742, the mine owner, John Lemon (whom Lemon Street and Lemon Quay in Truro are named after), bought five steam engines but his main plan for drainage was to drive a 4km long adit known as the Poldice Deep Adit from near Twelveheads to the deepest point possible on the edge of the Poldice sett. Tunnelling began in 1748 and was carried out using gunpowder and hand tools and the adit was in use by the mid-1750s.
During the 1760s, the Poldice Deep Adit was extended to drain more of the mines in the Gwennap area and by the 1770s the network was known as the Great County Adit. Further branches were added during the late 18th and early 19th centuries. It eventually consisted of nearly 40 miles of underground tunnels, providing drainage to over 60 mines. In 1839, it discharged over 14.5 million gallons per day into the Carnon River. Although it is unmaintained, it still drains many of the abandoned underground workings today; in the summer of 1980, the flow was measured at half a million gallons per day.
When digging horizontal tunnels such as adits, miners were paid by the fathom of tunnel. However, the miners realised that, upon reaching hard rock, rather than take ages to dig through it, it would be more profitable to veer off into softer rock to bypass it and dig more distance per day. The result was a meandering, wonky adit. Mine owners consequently changed the pay scale to the distance as the crow flies to provide incentive for a more direct route.
Twelveheads gets its name from the stamping mill that was in operation here with twelve (ore-crushing) heads. We can tell this refers to Cornish Stamps as these were normally produced in banks of four whereas Californian Stamps were in fives.
Buddleia are originally from northwest China and Japan where they grow in forest clearings, on riverbanks and on limestone outcrops where they are able to survive with minimal nutrients. They were introduced into the UK as an ornamental plant in the late 19th Century and can found in many gardens. Some have escaped and established a niche on industrial land which resembles their native limestone outcrops.
The shrub is commonly known as the Butterfly Bush as the flowers are profuse, rich in nectar and are in the shape of champagne flutes; butterflies and bees have sufficiently long drinking apparatus to reach the bottom.
The plant has two types of leaf; the broad green leaves are replaced with shorter hairy grey leaves during the winter which are more resistant to frost and the drying effect of cold winds.
The conical structures in the old dressing floors are the remains of devices known as "buddles". These were used to separate the ore from the rock (known as gange) in the ore slurry created by the stamping mill. The slurry was trickled onto the centre of the dome and a rotating set of brushes, suspended from wooden spokes, smeared the slurry around the circular structure. The heavy ore fragments would deposit near the central dome whereas unwanted rock fragments would travel further and end up in a pit around the outside.
Tungsten (also known as Wolfram) is a rare metal which occurs as mineral compounds such as Wolframite (an oxide with iron and manganese). Tungsten is the hardest of all metals and has the highest melting point, imparting these properties when a steel alloy is made containing tungsten. This made it in great demand for arms in the World Wars. It still has many different modern-day uses including cutting tools, electronics, turbine blades and rocket nozzles.
Pasties became popular with miners initially as a meal that could easily be carried to work though some mines eventually had stoves so a batch of pasties could be lowered down raw and baked fresh at the bottom of the shaft. Mines were very wet places so keeping a pasty dry for several hours would have been a real challenge.
The popular story of pasties eaten in mines being held by their crimped crust which was then discarded is likely to be an urban myth. As well as the difficulty of holding a "man size" pasty by its crimp without it snapping off. You can try this experiment for yourself with a "large" (enormous) size Philps pasty (but not on a harbour wall). Miners were generally too poor and hungry to throw away food. Photos from the 1890s show miners with pasties wrapped in a cloth bag to keep them clean down a mine. Some researchers (very dedicated to the pasty cause) have checked through thousands of photos and found none where a miner is holding a pasty by its crimp.
The jay is a member of the crow family recognisable by the flash of electric blue on their otherwise brown body. Their natural habitat is woodland, particularly oak.
Like squirrels, jays collect and bury acorns as a winter food store. Once jays were the main means by which oaks colonised new locations as a population of 65 jays can bury (but not always find again afterwards) half a million acorns in a month. Jays prefer to bury their acorns in open ground which is an ideal spot for a new oak tree.
Several species of heather grow in Cornwall and are most easily recognised when they flower from July to September. The one with the most brightly coloured (purple) flowers is known as bell heather due to the bell-shaped flowers. This is the earliest one to start flowering - normally in June. Bell heather is usually interspersed with ling or common heather which has much smaller flowers which are usually paler and pinker and come out at the start of July. A third kind known as cross-leafed heath is less abundant but can be recognised by the pale pink bell-shaped flowers that grow only near the tips of the stems, resembling pink lollipops. A fourth species known as Cornish heath grows only on the Lizard and has more elaborate flowers which are mostly pale with a dark purple crown at the front.
Heathers and heaths are members of the Ericaceae family. The formal definition of a heather is a member of the Calluna genus within this family whereas heaths are members of the Erica genus. Bell heather is actually an Erica and therefore technically not a heather but a heath.
Heather plants have a symbiotic relationship with fungi which grows inside and between some of the plant root cells. Up to 80% of the root structure can be made up of fungi. The fungi are able to extract nutrients from poor, acidic soils that plants struggle with. In return, the plant is able to generate other nutrients (e.g. sugars by photosynthesis) that are useful to the fungi. A similar partnership between plants and fungi occurs in lichens.
Heather can grow in soils which have concentrations of metals normally considered toxic to other plants and they are also tolerant of salty (high sodium) environments on the coast. Their symbiosis with fungi restricts metal uptake through their roots.
Heather plants can live up to 40 years and over time they form woody stems. This provides them with a way of excreting heavy metals that they absorb by locking it up in the layers of dead wood (found by researchers as the areas in the plant with the highest concentrations). Their woody stems have also found many uses over the centuries including fuel, thatch and ropes. One other use has made it into the genus name for heather - kallune is Greek for "to brush".
The large round chimney with an octagonal base dates from around the early 19th Century and is known as "the clock tower". This is because as well as doubling as a flue, the tower contained a clockwork mechanism which would ring a bell at the end of a shift. There was a staircase within the tower leading up to a wooden floor.
Once rendered into a powder, the tin ore was separated from fragments of less useful rock, usually using water and taking advantage of the heavier tin ore sinking more quickly out of a suspension than the other minerals. The slurry was sometimes run slowly down an inclined wooden board: the heavier tin fragments would settle near the top and could be scraped off whereas the fragments of lighter rock could be discarded from the bottom, and the material in the middle could be recycled into the next batch. Conical structures (known as "buddles") with rotating brushes were also used. It's possible that the Cornish mining word for the waste sludge of rock fragments - gange - is the origin of the English slang word "gunge".
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