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Dolcoath Mine
Brea, Camborne, Cornwall, UK
associated engineer
Richard Trevithick
date  1720s - 1921
era  Georgian  |  category  Mining/Quarrying  |  reference  SW660404
Dolcoath Mine was known as the Queen of Cornish mines. Primarily it supplied copper but also produced tin, silver and many other minerals. When it closed in 1921, it was the deepest of any mine in Cornwall. Nowadays, the site is mostly derelict. Early on, two Richard Trevithicks worked there: father and son.
The mine probably began operating in the 1720s. The first documented reference to it dates from 1738. It was a ‘cost book’ mine, a term that meant that a minimum of six shareholders, or ‘adventurers’, took shares and signed for them in a cost book held by a purser. At each meeting of the adventurers, profit or loss was distributed according to shareholding. The area of the land from which shareholders were allowed to extract minerals was called the ‘sett’.
Originally, Dolcoath Mine was drained using water-powered pumping and winding engines fed by leats (artifical watercourses). In 1765, mine captain Richard Trevithick senior (1735-97) supervised construction of a new deep adit (near horizontal tunnel) to drain the workings. Ten years later he took charge of re-erecting a second-hand Newcomen atmospheric engine bought from Carloose Mine for £414. He redesigned its boiler and installed self-acting gears and valves — doubling its efficiency and increasing the final cost to £1,349.
Competition from mines at Parys Mountain in Anglesey, where ore was easier to extract, and the collapse of the Cornish copper standard, caused Dolcoath to close 1788-98, re-opening in 1799. At its peak, the mine produced almost 10,000 tonnes of copper ore in a single year — and a total of 245,386 tonnes between 1815 and 1856.
Trevithick's son, the well-known Cornish engineer Richard Trevithick (1771-1833) was first employed at Dolcoath in 1786, earning 24 shillings (£1.20) per month. Later, in 1801-2, he designed an engine for the mine in which steam was exhausted into the atmosphere rather than into a condensing vessel (the arrangement in Watt engines). Trevithock's engine was dubbed the Valley Puffer after the noise of the escaping steam.
In 1805-6, a horizontal non-condensing whim engine was built to Trevithick’s design under mine captain Andrew Vivian (1759-1842). A whim is a winding drum with a vertical axis. In February and March 1806, this whim engine was tried against a Boulton & Watt atmospheric whim engine that had been originally installed (1784) at Wheal Maid near Carharrack. At first the Boulton & Watt engine worked more efficiently but after Trevithick reduced the length of his fire grate, his engine raised three times more ore in a fortnight than the other.
Trevithick's engine's bolier was 1.63m diameter and 3m long, made from wrought iron plates 12.5mm thick, with cast iron ends 25mm thick. It was heated by two internal tubes tapering from 760mm to 460mm. The fireplace was 910mm long, 710mm wide and 270mm thick. Its chimney was 9.1m high and about 400mm in diameter, made from 3mm sheet iron. The engine’s cylinder was 280mm in diameter and worked a 2.44m stroke at 30 strokes per minute.
The boiler with internal fire tube that Trevithick pioneered was to become widely known as a ‘Cornish boiler’. In 1811-2 he harnessed three of them to existing Boulton & Watt engines — first to a 1.6m diameter cylinder engine, and later to a 1.93m diameter cylinder one. Initially he used two boilers, each 1.52m in diameter and 5.49m long with oval fire tubes 1m by 900mm. However, he soon added a third boiler 1.88m in diameter and 6.71m long with a circular fire tube tapering from 1.22m to 900mm in diameter. This arrangement worked until 1869.
At its height, 1,600 people were employed at Dolcoath Mine, and in 1864 there were ten engines, seven waterwheels and one main engine at work there. It was a busy place. In 1876 it was said of the mine that "the deeper it goes, the richer it gets" — the main lode was between 5.5m and 16.5m wide below 400m. And the mine was deep. By 1778 the workings were 293m down and by 1824 they were at 439m. As 1836 came around, the copper veins were becoming exhausted and from 1844 onwards the mine went even deeper in order to exploit tin ore deposits. Copper extraction ceased in 1878.
Dolcoath took over Bullen Garden Mine (date unknown, probably before 1765) and Eastern Stray Park Mine in 1871. In 1895, it became a limited liability company and around 1898 acquired the mines of Camborne Consols, Camborne Vean, Cook’s Kitchen, Stray Park and Wheal Harriett, plus parts of the mines at Roskear and Pendarves United.
Dolcoath was the leading British tin producer until World War I (1914-18). Thereafter, the price of tin was falling and by the time the mine was abandoned in 1921, it was over a kilometer deep and had some 110km of underground passages. Between 1799 and 1920, Dalcoath had sold ores worth more than £10m, including copper, tin, silver, pyrites, bismuth, wolfram, galena, arsenic, cobalt, tungsten, zinc, nickel and amethyst. Its estimated lifetime production was 355,000 tonnes of copper ore and 81,000 tonnes of black tin ore.
In 1929 a new 610m deep shaft was driven at Roskear (SW653411) in order to try to re-open the northern part of Dalcoath Mine but the attempt was abandoned when little tin ore was found. South Crofty Mine (SW663410) acquired the Dolcoath sett in 1936.
Today, the Dolcoath Mine site spreads across the Tuckingmill Valley and is dotted with relics of its former above-ground infrastructure. This includes the remains of an engine house over Harriett’s Shaft (SW657402), which was built in 1860 for a beam engine with a 1.52m diameter cylinder (later fitted with a 1.65m diameter cylinder).
There are three other Grade II listed buildings on the site. One is the now-roofless granite house built in 1895 for a Morgan winding engine that traversed 4.9m to and fro on rails at William’s Shaft (SW661399) — the deepest of all Dalcoath’s shafts. The second is a slate-roofed killas rubble compressor house, with granite chimney stack, at New Sump Shaft (SW660404) dating from 1886 and built for a 300mm diameter Holman air compressor that supplied air 800m below ground. Lastly, there's a derelict granite winding engine house at New East Shaft (SW661404) with an attached roofless boiler house.
Research: ECPK
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Location

Dolcoath Mine