Wheal Maid and Poldice Valley circular walk

Wheal Maid and Poldice Valley

A circular walk in the area described in Victorian times as the richest square mile anywhere on Earth

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The walk starts at Twelveheads and follows the trackbed of the railway to the lagoons created by the Wheal Maid tailings dams. The walk continues to Crofthandy where it joins a byway leading to the Poldice mine workings. After passing the mine buildings, the walk follows the Poldice Valley, gradually descending to join the Mining Trail. The final section of the walk follows this back to Kilcor Stamps and Twelveheads.

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Vital statistics

  • OS Explorer: 104
  • Distance: 3.4 miles/5.4 km
  • Steepness grade: Easy-moderate
  • Recommended footwear: walking boots

OS maps for this walk

OS Explorer 104 OS Explorer 104 (laminated version)

Click or tap on map for more info (blue=laminated)


  • Mining Heritage
  • Bizarre landscape of coloured minerals

Adjoining walks


  1. Follow the lane from the lay-by into Twelveheads to reach a bend at the Playing Field sign where a mining trail departs ahead to Portreath and left to Carharrack.

    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.

  2. Turn left onto the track signposted for Carharrack and follow it uphill to where a signposted path departs to the right.

    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.

  3. Turn right onto the narrow path and follow it to reach a wooden post with a Mining Trail sign.

    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.

  4. Continue on the path as indicated by the Mining Trail arrow and follow it to reach a Gwennap Parish sign.

    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.

  5. Continue ahead to join a tarmac path. Follow this between the mine tips and alongside the lagoon to reach another Gwennap Parish sign with information about John Taylor.

    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.

    More about the Wheal Maid lagoons (aka Cornish Mars).

    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).

  6. Continue ahead on the track for about 30 metres from the sign then bear right onto the narrow, stony path leading up onto the top of the embankment. Follow the path along the top to reach the remains of an old sign on the far side at a junction of paths.

    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.

  7. At the junction beside the sign, turn left and follow the path through a kissing gate to reach a track. Bear left onto this and follow it until it forks.

    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 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.

  8. Bear right at the fork then follow the track until it eventually ends on the road.

    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.

  9. Turn right onto the byway indicated for the Poldice Terrace and follow the track to a fork where a track continues ahead signposted for Pensilva.

    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".

  10. Continue ahead in the direction of Pensilva and follow the track past the entrance to Pensilva until it splits again.

    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.

  11. Continue ahead on the track to reach a fork in front of a large chimney.

    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.

  12. Turn left at the chimney to reach another junction of tracks just past it.

    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.

  13. Turn right and follow the track to reach another junction.

    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.

  14. Turn right and follow the main track to where it splits into 3 paths.

    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.

  15. Turn left onto the largest of the paths leading downhill. Follow this, keeping the concrete structures on your left, until you emerge onto a wide track.

    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.

  16. When you reach the level area, turn right and then follow the lower of the two paths to meet a fence. Continue along the fence until the path forks.

    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.

  17. Bear right onto the path leading uphill slightly and follow it to a junction of paths.

    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.

  18. Bear right to follow the path uphill and emerge onto a larger path.

    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.

  19. Turn left and follow the path in a gradual descent along the valley, ignoring any smaller paths to the left, to where the path main path forks.

    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.

  20. Keep right to join the small path leading ahead and follow this to meet the main track along the valley at a waymark.

    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.

  21. Turn right and follow the track until it emerges onto another track opposite the gates of Killicor Stamps.

    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".

  22. Bear left and follow the track for half a mile back to Twelveheads, continuing ahead onto the lane to retrace your steps to the lay-by.

    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.

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