Conservation of nationally significant mining sites
Since 2021 we’ve been surveying four former mining sites in the Tamar Valley. All of the sites are protected as Scheduled Monuments and, at the time of writing, were still recorded on the Historic England Heritage at Risk Register. Our aim? To prepare updated assessments of their condition, along with a prioritised conservation plan, to help arrest their declining condition.
The sites include Gunnislake Clitters, New Consols Mine, Luckett, and Holmbush Mine, all on the Cornish side of the Tamar, as well as Gawton Mine, which is on the eastern banks, in Devon. These mines were mainly in use during the second half of the 19th century, when, at first, the principal focus was on copper and tin mining. However, as these valuable metal ores were mined out, there was an increased emphasis on arsenic production, which became increasingly profitable as the century progressed.
Refined arsenic was produced by roasting the arsenic containing ores on a rotating hearth, in what was effectively a large oven, called a calciner. The resulting hot vapours were then drawn along connecting flues, some up to 500m long, before being dispelled through a chimney, often situated upslope away from people, to avoid poisoning mine workers and local villagers. At Gawton Mine, the original chimney had to be relocated a greater distant up the valley side, as noxious vapors had been making children at the nearby school very ill. Within the flues, as the vapour cooled, arsenic crystals precipitated onto the walls and at collection chambers or ‘winding labyrinths’ situated along the flue’s length, before reaching the chimney. Shockingly to us nowadays, the arsenic residues were usually scraped from the walls and collected by young children, who were small enough to readily enter these confined spaces.
As might be imagined, arsenic and heavy metal contamination remains a serious health and safety consideration when managing the conservation of these mining sites. In places, these residues are still evident, particularly on the interior surviving walls of calciners, flues, and other buildings associated with the refining and storage of arsenic.
Across the mines a range of structures and still features survive. These include engine and boiler houses, calciners, flues, storage buildings, reservoirs, smithies, mine Captain’s houses, processing floors, spoil heaps, and administrative buildings, as well as crushing and grinding houses which were the first stage in breaking down the mined ore for processing. It was the job of the engine houses to supply energy for the mine, keep the underground workings clear of water, and raise mined ore to the surface. They also powered the crusher houses and the numerous tramways used to transport materials around a site.
The different buildings survive in a variety of ruinous conditions but, in truth, most are in desperate need of conservation, having been enveloped within the mixed woodland that, during the 20th century, has once again gained ascendancy on the slopes of the Tamar. Crusher and grinder houses are at particular risk, as the vibrations associated with the operation of heavy crushing and grinding equipment necessitated a greater use of wood in the building’s construction. Needless to say, the wood has survived less well than other masonry elements, increasing the general level of dilapidation.
As part of our surveys we’ve called on the expertise of both ecological and structural surveyors – it’s been a priority to weave together archaeological and ecological objectives, and to optimise the potential for enhancing the natural environment of the sites through sympathetic management.
Drone and photogrammetry surveys have provided a detailed visual record, at a snapshot in time, and enabled the creation of 3D models of the most complete and important surviving structures. The comparison of this photographic and video record with future surveys will help us to track how the monuments are coping with the passage of time, and see where conservation works have helped prevent, or at least to slow, their decline. If you’re interested, these models are feely available to view on Sketchfab, just follow these links for each mine: Gunnislake Clitters, New Consols, Holmbush, and Gawton Mine.
Moving forward, it’s hoped that these nationally significant sites can secure the necessary funding to implement the proposed management recommendations, and that they can be consolidated for future generations to appreciate. Although, as might be imagined, the costs for carrying out what are often extensive structural repairs, in quite remote and difficult locations, can be eye watering.
Senior Heritage Consultant
This work was commissioned by Tamara Landscape Partnership, who are funded by the National Lottery Heritage Fund, along with supporting grants from Historic England. The work forms part of a wider Monument Management Scheme for capital works and enhanced management within the Tamar Valley for Scheduled Monuments.
A video explaining more about the work and objectives of the Tamara Landscape Partnership can be found at: https://www.youtube.com/watch?v=5Vo_sxIVHIo