Wheal Unity

Wheal Unity

Wheal Unity Location in Cornwall
Location	Mullion, Cornwall, England 50°00′38″N 5°14′50″W / 50.01064°N 5.24713°W / 50.01064; -5.24713
Products	Copper
Type	Underground
Active	1741–1852[1]

Wheal Unity was a copper mine near Mullion on the Lizard Peninsula in Cornwall, England. It formed the largest of a group of copper workings in the valley south-east of Mullion Cove, known in some older accounts as Ghostcroft Valley.^[2] Mining was intermittent, with the economic historian Christopher J. Schmitz dating the operation of Wheal Unity from 1741 to 1852.^[1]

The mine was particularly noted for unusually large masses of native copper. In 1912 the geologists J. S. Flett and J. B. Hill described the specimens obtained from the workings as the largest blocks of native copper to have been mined in England.^[2] A mass from Wheal Unity was exhibited at the Great Exhibition of 1851.^[2]

Copper working around Mullion was established by the mid-18th century. Flett and Hill noted that William Borlase, in his 1758 Natural History of Cornwall, described native or "virgin" copper obtained in Mullion parish in lumps weighing several pounds, including one of 40 lb (18 kg). They considered this evidence that copper workings already existed in the district at that date.^[2]

The early history and identity of the individual Mullion workings are not completely clear. Flett and Hill stated that they could not establish whether Wheal Unity was the oldest mine in the district. They also noted that copper mines near Mullion had ceased working before a geological account of the Lizard district was published in 1818.^[2] Later mining historian A. K. Hamilton Jenkin devoted several pages to the Mullion mines, while Schmitz gives 1741 as the beginning of the period during which Wheal Unity was worked.^[1]

The most important later workings were in the mid-19th century. Flett and Hill recorded that a substantial amount of copper was obtained around 1847 from Trenance Mine, situated in the same valley, which they considered to be "probably" the same mine as Wheal Unity.^[2] The material raised was principally native copper, although large pieces of grey copper ore were also found.^[2]

Contemporary reports cited by the Geological Survey described an exceptionally large slab of native copper raised in 1847. It measured 7 ft 6 in (2.29 m) in length, about 2 ft (0.61 m) in average breadth, and between 4 and 12 in (10 and 30 cm) thick.^[2] Flett and Hill considered this slab probably to have been the mass subsequently sent to the Great Exhibition of 1851. They also reported contemporary accounts of still larger masses underground which had to be broken up before they could be brought to the surface.^[2]

Schmitz, discussing commercially exploited native-copper deposits internationally, identified Wheal Unity as a notable British example. He stated that the mine yielded a considerable quantity of native copper between 1741 and 1852 and recorded a slab weighing 71.1 kg (157 lb) that was raised in 1848 and presented to the Geological Museum in London.^[1]

The Geological Survey regarded Wheal Unity as the largest of the Mullion mines and the last of them to be discontinued. It was unable, however, to locate plans of the workings or reliable statistics for the mine's total copper production.^[2]

Wheal Unity lies within the rocks of the Lizard complex. The Geological Survey recorded fragments of native copper, malachite and chrysocolla on the spoil from the larger copper mines of the Lizard district, whose country rock was serpentinite. Around Mullion, native copper was found in veins and irregular masses within the serpentinite.^[2]

Flett and Hill interpreted the economically significant copper as having undergone secondary concentration along joints and fissures, probably through circulating water. At the principal mines, copper ores were associated with brecciated and crushed serpentinite along zones of displacement. They reported that the matrix surrounding the large Wheal Unity copper mass exhibited in 1851 consisted of brecciated and decomposed serpentinite, which they regarded as evidence for deposition along a fracture or movement plane.^[2]

Native-copper deposits were commercially exploited at relatively few locations worldwide. In a study of the development of the world copper industry, Schmitz cited Wheal Unity alongside other examples of commercially worked native-copper deposits, although on a much smaller scale than the major deposits of the Keweenaw Peninsula in Michigan.^[1]

In 1912 Flett and Hill recorded two partly infilled shafts at Wheal Unity, together with remains associated with the mine, about half a mile south-east of Mullion Cove.^[2] They also suggested that old workings visible on the coast south of the cove might have communicated with Wheal Unity, but did not establish the connection as certain.^[2]

The former mine site is centred near Ordnance Survey grid reference SW674173. A photograph taken in 2011 identifies scrubland at the site of the mine.^[3]

• Mining in Cornwall and Devon
• Mullion Cove
• Lizard complex

• Hamilton Jenkin, A. K. (1967). Mines and Miners of Cornwall. Vol. XIII: The Lizard–Falmouth–Mevagissey. Truro: Truro Bookshop. pp. 7–13.

• Mullion Mine – Northern Mine Research Society