Reasons for Designation
For several millennia the south west peninsula has been one of the major areas
of non-ferrous metal mining in England, its more important and prolific
products including copper and tin, along with a range of minor metals and
other materials, notably arsenic, which occur in the same ore bodies. Before
the 16th century, exploitation of this region's non-ferrous metal resources
almost exclusively involved tin. Extraction focussed along valley floors and
hillslopes on and around the granite uplands of the south west where tin ore,
cassiterite, had accumulated after natural erosion from the parent lodes.
These accumulations were exploited by streamworks, using carefully controlled
flows of water to expose and then concentrate the ore, leaving behind
distinctively deepened valley floors with various patterns of spoil heaps,
together with extensive water management features and downstream silting. By
this method, Dartmoor became Europe's chief source of tin in the 12th century
with a further peak of production between about 1450 and 1550. By the early
post-medieval period, most substantial deposits susceptible to streamworking
had been exhausted and the focus of exploitation transferred to the
mineralised lodes themselves, a change which also marks the appearance of
copper as an important product of the south western mining industry. The early
post-medieval extraction from lodes was restricted by the ability to drain the
cut, resulting in relatively shallow workings directly into lode exposures at
the bedrock surface, often by pits, called 'lode-back pits', sometimes
enlarged to form longer openworks along the lodes. Tin ore from later medieval
and early post-medieval extraction sites was processed and smelted using
water-powered tin mills sited nearby.
In the 18th century, ore extraction and processing rapidly expanded to meet
growing demands, aided and promoted by technological development, with ore
shipped to Bristol and later South Wales for smelting. Surface workings became
larger and more extensive, and deeper extraction was achieved from shafts, the
water pumped from larger mines by early steam engines or drained through
near-horizontal tunnels called adits which also served to access the lodes.
Horse powered winding engines lifted ore from the shaft while larger and more
efficient waterwheels served ore processing areas. By such means, west
Cornwall became England's main producer of copper ore in the 18th-early 19th
century. Intensification accelerated in the late 18th-early 19th century with
more efficient steam powered pumping engines allowing deeper shafts from which
extensive underground workings spread out. By the mid-19th century, steam also
powered winding and ore processing operations, the engines, boilers and
ancillary machinery housed in distinctive masonry buildings grouped around the
main shafts and dressing areas. Later in the century, compressed air was used
for underground extraction equipment, fed from steam powered compressors on
the surface. Ore processing became increasingly mechanised, along with the
development of more effective methods of separating and retaining different
ores, particularly in the production of arsenic which became a major saleable
product in the 19th century, with the south west mines forming the world's
main producer. The transport systems serving mines was also revolutionised in
the 19th century, with tramways replacing packhorse and cart tracks; later,
railways were built specifically to provide fuel and materials to mines and to
export their ore. With these advances, east Cornwall and west Devon became one
of the world's main sources of copper ore until the later 19th century, while
in west Cornwall the copper ores became exhausted and replaced as that area's
main product by the tin ores present at deeper levels. From the 1860s, the
south western mining industries declined with competition from cheaper sources
of copper and tin ore overseas, especially from South America, leading to a
major economic collapse and widespread mine closures in the 1880s. Limited
ore extraction continued into the 20th century, some from shaft mining, but
attention mostly turned to reprocessing spoil from earlier mines. Among the
developments to make these activities cost effective, electric power and
internal combustion engines increasingly replaced steam for ore processing,
winding and pumping in the early 20th century, activities which were housed in
large framed sheds rather than masonry structures. Ore processing underwent
further advance and the invention of electro-magnetic separators enabled
efficient extraction of the tungsten ore wolfram. Urgent demands for metals
during the First and Second World Wars led to the reopening of several mines
and reprocessing mills, with wolfram a particularly important ore, but
slumping ore prices between and since the wars curtailed any profitable
development of these enterprises.
The 19th-early 20th century mine at Gunnislake Clitters has a good range
of surviving remains from an unusually long sequence of operational phases,
spanning much of the most intensive period of metalliferous mining in
Cornwall. The upstanding features and buildings are complemented by areas of
the mine's early processing activities sealed beneath the later dumps. The
dumps themselves, from the various phases, are of particular importance in
preserving particle size and colour differences denoting their functional
association with the surviving processing structures from which they derive.
The successive remains in this scheduling demonstrate clearly the varied
impacts of technological development in extractive and ore processing methods
throughout the mine's operational life, to the extent of adding a further ore,
wolfram, to the mine's main products during the early 20th century. Such
development is also clearly evident in the remains of the mine's supporting
infrastructure: the appearance of complexes of masonry buildings in the mid-
19th century and their replacement with large framed sheds in the early 20th
century; the extensive (though not total) replacement of water power by steam
power in the 1860s and the installation of electric power in the early 20th
century, and the replacement of trackways with tramways and the arrival of the
railway at the edge of the mine's area in the later 19th century. These
developments and the mine's periods of prosperity and closure also partly
reflect changes in funding strategies and the wider economic context in which
the mine operated, aspects which are well recorded for this mine in a wealth
of historical documentation.
Details
The monument includes the remains of the Gunnislake Clitters Mine, a
19th-early 20th century copper, tin, arsenic and wolfram mine on a steep
slope down to the River Tamar 1km WNW of Gunnislake village in south east
Cornwall. The riverside pumping engine house and chimney in this
scheduling are listed Grade II. The scheduling is divided into four
separate areas of protection.
The earliest visible remains on this steep slope south of the River Tamar are
scattered early post-medieval workings within and beyond the scheduling,
including deep openworks, pits and small shafts dug into the mostly east-west
mineralised lodes. More intensive mining activity began about 1820: a long
tunnel called an adit was driven south into the foot of the slope near the
river, reaching over 900m in length. Cutting across successive lodes, it gave
access to and drained water from workings and shafts extending from it. This
early stage of the mine, called `Were Fox', had dressing floors and spoil
dumps beside the adit entrance in an area now masked by later dumps. A water
wheel in the adit outflow powered dressing floor machinery and drove a fan to
clear air in the mine. An underground waterwheel was later installed to pump
water up to the adit from working levels extending below river level. By the
time operations ceased in 1827 it had produced 40 tons of copper ore.
Reopening as the `Clitters Adit' mine in 1858 and renamed the `Gunnislake
Clitters' mine in 1877, it continued production of copper, tin and arsenic
until closure in 1889 at a time of widespread economic failure of Cornish
mining. In this highly productive phase, the mine sold 32,686 tons of copper
ore from 1860 to 1890 and 123 tons of tin ore from 1867 to 1873. Extraction,
crushing and primary dressing were focussed around Skinner's Shaft, sunk deep
into the main lode from the hillside 450m south of the original adit. Final
ore dressing and concentration, and arsenic production, were sited over the
lower slope behind the early phase adit. Extensive remains from this phase
survive in both areas. Skinner's Shaft itself, eventually sunk to over 500m
deep, is enclosed by a rectangular rubble wall with dressed quoins. In
1862-1864, steam engines were installed for pumping, winding and ore crushing,
in engine houses which survive extensively at the Skinner's Shaft complex. The
pumping engine house, north west of the shaft, is adjoined to the north by the
largely intact walls and one extant gable of the boiler house which served all
three engine houses in this complex. A building by the boiler house is
identified as a miners' dry, where clothing was dried between shifts. A tall
detached chimney serving the boiler house rises 20m to the west, largely of
mortared rubble but with a brick-built upper quarter. The winding engine house
is 13m north east of the shaft, with a partly demolished ore crusher house
close to the south east. A building complex south west of the shaft includes
the Account House, with a bay window facing east, and buildings and a yard
identified as the carpenters' workshops and store.
Extending 75m east from Skinner's Shaft is a large dressing floor, terraced
along the slope and revetted by tall rubble walls; a map of 1883 shows the
floor occupied by a long shed which has not survived. East of the dressing
floor, a row of six small rectangular settling tanks survives, silted but with
sluice gaps evident in their downslope walls; incomplete remains also survive
from one of two larger tanks shown nearby on the 1883 map. South of the
dressing floor's east end, an ore crusher building survives substantially
intact and was powered from an engine house surviving adjacent to the south
west beside the Dimson to Chilsworthy road. South of that road, walls survive
of the 1860s miners' dry and smithy, alongside the levelled platform of a
former forge. East of these buildings, the 1883 map shows reservoir ponds
serving the boiler house; no remains of these are now visible.
Extensive spoil dumps cover much of the hillslope below the Skinner's Shaft
complex, down to the Dimson to Bitthams road. Early photographs and the 1883
map show them as much larger than they now survive and forming long `finger
dumps' supporting tipping tramways emanating from the north of the dressing
floor and the ore crusher by the Skinner's winding house. Their present extent
results from 20th century reprocessing but the various dumps retain their
differing particle sizes and colours corresponding to the stage of ore
processing from which they derive.
The west of the Skinner's Shaft dressing floor was linked to the lower slope
dressing floors and arsenic works by a tramway between two finger dumps and
extending north of the Dimson to Bitthams road. It does not survive south of
that road but about 90m of its course remains visible north of the road as a
rubble-faced embankment running to a cutting before the truncation of its
northern end by the western tramway of the 1900-1909 works.
The lower slope operations were sited on terraces retained by high revetment
walls. The 1883 map shows two rows of rotating waste/ore separators called
buddles: six on an upper level and three below, associated with settling
tanks. At the east of this complex, arsenic extraction structures were linked
by a tortuous flue called a labyrinth to one of two detached chimneys. The
20th century reprocessing works and its dumps masked and partly removed a
number of these lower slope features of the 1860s-1880s phase. The terraces
survive well, as do the two chimneys and a reservoir, still water-filled,
which supplied water to the dressing floor. Masonry survives from several
buildings near the western chimney and others associated with the arsenic
works further east, but the buddles, settling tanks and arsenic labyrinth were
variously dumped over or removed by the later activity. Below the lower
dressing floor is the 1860s smithy and office, with walls and chimney
extensively intact. Close to the north, by the river, are extensive remains of
another complex comprising a pumping engine house, adjacent boiler house,
detached chimney and two settling tanks. These were built in 1882 to supply
clean river water to the Skinner's Shaft boiler house and to augment water
supply to the lower slope dressing floor. By then, the Clitters Adit outflow
had been diverted 25m to the east, passing over a waterwheel before joining
the river. The 1882 engine house was built over the wheel pit, which was left
open and through which the adit outflow still passes. Water was fed to the
engine house by a leat cut along the riverside and taken off the river at a
weir 175m upstream of the engine house.
The main export route for the mine's ore in the 1860s-1880s was a track from
the lower dressing floors to the riverside and on, beyond this scheduling, to
the head of the Tamar Navigation at Gunnislake. From at least 1872 and
possibly earlier, the East Cornwall Mineral Railway ran from above the
important quay at Calstock, passing south of the Skinner's Shaft complex,
where sidings in this scheduling were built to unload materials required in
the mine's operation.
In 1900, a new company, Clitters United, amalgamated this mine with three
others nearby. Minor underground work required a small powder magazine which
survives upslope from the Clitters adit but the main investment lay in a large
ore reprocessing mill built on the lower slope in this scheduling, east of the
earlier lower dressing floor. It housed the latest electric powered equipment
for extracting tin, wolfram and arsenic from spoil dumps around this and other
nearby mines, especially from the Greenhill arsenic works on the upper slope
beyond Skinner's Shaft. The mill's surviving remains extend across five
revetted terraces, to 50m long, supporting concrete floors and an array of
rendered machine bases. Contemporary photographs give external and internal
views showing the mill's now demolished structure of timber and girder framed
sheds with corrugated sheet walls pierced by rows of windows. Coarse waste was
carried west by a short tramway and dumped over the buddles and tanks of the
earlier lower slope dressing floor. A new dressing floor was built near the
mill, its terraces surviving with two pairs of buddles and the wheel pit from
which they were driven. Fine waste tailings were taken west of the 1882
riverside engine house and settling tanks to form a massive dump, 100m long,
towering above the riverside. East of the dressing floor, surviving terraces
of an ore drying plant support its kiln, white brick chimney and tank. South
west of the mill's dressing floor was the focus of arsenic extraction;
surviving remains include a Brunton calciner retaining its brick arched lower
vault, hearth bed, central spindle, drive gear and lower bearing plinth. From
there, the arsenic flue reuses elements of the earlier flue and passes
beneath the floor levels of several buildings in its circuitous route to the
western of the earlier chimneys. Steep inclined tramways brought ore and other
materials to the mill and carried dressed ore from it. A western tramway rose
from above the mill, passing 75m west of Skinner's Shaft, to enlarged sidings
by the railway line above; its crossing over the nearby road is marked by a
tall masonry abutment on the south. Its course down the slope remains clearly
visible, with embankments and cuttings to smooth its gradient. An eastern
tramway, also still visible, rose from above the mill to a blocked adit by the
Dimson to Bitthams road; several lengths of tram rail survive as fence posts
along a nearby field wall to the west. A third tramway descends to the
riverside from the lower end of the eastern tramway, on almost the same
alignment, and met a tramway along the former riverside track to Gunnislake.
The reprocessing works produced 547 tons of tin ore and 443 tons of wolfram
between 1902 and 1908 but it ceased operation in 1909.
Following the outbreak of war in 1914, the mine was reopened for reprocessing
ore for wolfram and tin. Some underground work was carried out but most ore
derived from existing spoil dumps as before, supplemented by ore brought by
aerial ropeway from reopened mines on Hingston Down and Kit Hill, beyond this
scheduling to the WSW. The ropeway was supported on shuttered concrete
stanchions; the two nearest the mine, in the south west of this scheduling,
carried the ropeway over the railway line. By 1919 the mine had produced 37
tons of tin ore but slumping prices after the war led to final closure of the
mine in the late 1920s.
The modern fences, gates, signs, signposts, goat sheds, and goat and poultry
keeping equipment are excluded from the scheduling, although the ground
beneath them is included.
MAP EXTRACT
The site of the monument is shown on the attached map extract.
