The Tolgus arsenic works 80m south east of East Tolgus House


Heritage Category:
Scheduled Monument
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Ordnance survey map of The Tolgus arsenic works 80m south east of East Tolgus House
© Crown Copyright and database right 2019. All rights reserved. Ordnance Survey Licence number 100024900.
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The building or site itself may lie within the boundary of more than one authority.

Cornwall (Unitary Authority)
National Grid Reference:
SW 68982 43025

Reasons for Designation

For several millennia the western part of the South West Peninsula, namely Cornwall and West Devon, has been one of the major areas of non-ferrous metal mining in England. It is defined here as prospecting, extraction, ore processing and primary smelting/refining, and its more important and prolific products include copper, tin and arsenic, along with a range of other materials which occur in the same ore bodies. Throughout much of the medieval period most of the tin was extracted from streamworks, whilst the other minerals were derived from relatively shallow openworks or shafts. Geographically, Dartmoor was at the peak of its importance in this early period. During the post-medieval period, with the depletion of surface deposits, streamworking gradually gave way to shaft mining as the companion to openworking methods. Whilst mining technology itself altered little, there were major advances in ore processing and smelting technologies. The 18th century saw technological advances turning to the mining operations themselves. During this period, Cornish-mined copper dominated the market, although it was by then sent out of the region for smelting. The development of steam power for pumping, winding and ore processing in the earlier 19th century saw a rapid increase in scale and depth of mine shafts. As the shallower copper-bearing ores became exhausted, so the mid to late 19th century saw the flourish of tin mining operations, resulting in the characteristic West Cornish mining complex of engine houses and associated structures which is so clearly identifiable around the world. Correspondingly, ore processing increased in scale, resulting in extensive dressing floors and mills by late in the 19th century. Technological innovation is especially characteristic of both mining and processing towards the end of the century. In West Cornwall, these innovations relate chiefly to tin production, in East Cornwall and West Devon to copper. Arsenic extraction also evolved rapidly during the 19th century, adding a further range of distinctive processing and refining components at some mines; the South West became the world's main producer in the late 19th century. From the 1860s, the South West mining industries began to decline due to competition with cheaper sources of copper and tin ore from overseas, leading to a major economic collapse and widespread mine closures in the 1880s, although limited ore-extraction and spoil reprocessing continued into the 20th century. A sample of the better preserved sites, illustrating the technological and chronological range, as well as regional variations, of non-ferrous metal mining and processing sites, together with rare individual component features, are considered to merit protection.

The Tolgus arsenic works survives very well, with little modification, containing the best preserved example of a Brunton calciner known to exist. The 20th century works contain a good range of surviving components. The adjacent survival and limited reuse of the 19th century arsenic works shows well the complexity and chronological depth often present at such sites.


The monument includes an early 20th century arsenic works which served the Tolgus tin stream works north of Redruth. The monument also includes adjacent remains of a 19th century calciner, flue and a collapsed chimney. The works' Brunton calciner, one of the arsenic condensing chambers, and the standing chimney are Listed Buildings Grade II. The early 20th century calciner is understood to be the only surviving complete example of a type that was developed by the Scottish engineer William Brunton. Constructed on this site in about 1933, its function was to roast off sulphur and arsenical contaminants from tin bearing ores. The arsenious oxide in the fumes was collected for sale from condensers higher up the slope. The fabric of the calciner is of reused granite blocks, some forming quoins to the wall corners, with uncoursed granite rubble in the upper section. Cream brick arches line the ground floor wall openings. The ground floor on the north side has a brick faced recess containing the calciner's twin grates, ash pans and damper door. The calciner has an hipped slate roof, painted fascia boards and a cast iron rain-water down-pipe on the north. The calciner's ground floor walling is reinforced with vertical iron tie-bars to counter the thermal stresses when in use. The eastern elevation contains the calciner's power arch which encloses the drive gearing for the rotating hearth which survives above. The calciner's exhaust opening and ore chute door are sited within the southern elevation. The first floor retains its original iron hopper to feed the rotating hearth, together with the floor's supporting beams and ties. The first floor also served as a storage space in which the ore was dried prior to being fed to the hearth below. The floor's access door is on the west, opening to the trackway beyond. The fuel store attached to the north of the calciner is constructed of cement-rendered concrete blocks and shuttered mass concrete, and was built about the same time as the calciner. The roof is only partly extant and is a mixture of cement-asbestos sheeting and felt-clad planks supported by wooden `A' frames that have been repaired in places. Upslope from the calciner are the flues and condensers that connect with the calciner, rising to a circular chimney 87m to the south west. The flues are brick with coursed slate-stone rubble in places. The flues' capping survives over some lengths, beneath a covering of earth and vegetation. The first condenser in the line of flues has the remains of seven brick baffles within, on which the arsenic would have accumulated and been periodically removed for further processing and sale. The second condenser, higher up the slope, is of a smaller three-baffle design and may have been added later than the flues and condenser lower down the slope. From the second condenser, a section of flue passes westwards under the Old Portreath Road and continues for a further 38m to join the circular chimney which bears the date 1933 and has a brick upper section. A revetted trackway cut along the hillside north from the calciner provided a sloping access ramp for the delivery of ores to the upper drying floor and hopper space. The trackway varies in width from a maximum 8.4m wide turning area at its southern end beside the calciner, to a minimum 4.5m at its northern extent. The rear wall of an earlier 19th century calciner extends south from the 20th century one; its extant walling was reused as the rear of a lean-to structure contemporary with the 20th century calciner. A line of tumbled masonry and a cone of soot stained slate-stone rubble mark the positions of a 19th century flue and chimney that ascended the hill slope immediately west of the 20th century calciner and its access trackway: some of the few surviving remains from arsenic calcining in the area before 1900. The surface of the modern metalled road is excluded from the scheduling, although the ground beneath is included.

MAP EXTRACT The site of the monument is shown on the attached map extract.


The contents of this record have been generated from a legacy data system.

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Books and journals
Mills, R, Schwartz, F, Johnson, M, The Mining Villages: An Exploration of the Gwennap Mining Area, (2000)
Sharpe, , Lewis, , Massie, , Johnson, , Engine House Assessment - Mineral Tramways Project, (1991)
Thomas, R, Pascoe, J, Manor of Tolgus, (1818)
Todd, , Laws, , Industrial Archaeology of Cornwall, (1972)
Title: 1st Edition 1:2500 Ordnance Survey Map Source Date: 1880 Author: Publisher: Surveyor:
Title: 2nd Edition 1:2500 Ordnance Survey Map Source Date: 1907 Author: Publisher: Surveyor:
Title: Redruth Parish Tithe Map CRO TM197 Source Date: 1841 Author: Publisher: Surveyor:
Tudor tin bounds in the Redruth area, Buckley A, (2003)


This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.

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