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Wheal Kitty 20th century tin processing works

List Entry Summary

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 Culture, Media and Sport.

Name: Wheal Kitty 20th century tin processing works

List entry Number: 1021164

Location

The monument may lie within the boundary of more than one authority.

County:

District: Cornwall

District Type: Unitary Authority

Parish: St. Agnes

National Park: Not applicable to this List entry.

Grade: Not applicable to this List entry.

Date first scheduled: 24-Feb-2004

Date of most recent amendment: Not applicable to this List entry.

Legacy System Information

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

Legacy System: RSM

UID: 35823

Asset Groupings

This list entry does not comprise part of an Asset Grouping. Asset Groupings are not part of the official record but are added later for information.

List entry Description

Summary of Monument

Legacy Record - This information may be included in the List Entry Details.

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 Wheal Kitty tin processing works contains a good, and relatively complete, range of surviving structural components, illustrating well the layout and construction of a tin ore processing works from the early 20th century. The Brunton calciners and scrubber chamber also demonstrate how 19th century technology and build was readily incorporated where appropriate and legally required to minimise arsenic pollution. The high quality of the works' survival is further enhanced by the nearby survival, beyond this scheduling, of parts of the shaft-head complex of buildings around the works' ore-source, Sara's Shaft.

History

Legacy Record - This information may be included in the List Entry Details.

Details

The monument includes an early 20th century tin processing works which served the Wheal Kitty mine at Goonlaze Downs, east of St Agnes in west Cornwall.

The Wheal Kitty tin processing works was constructed during 1926-29, its function being to process ore produced at the Wheal Kitty mine to extract cassiterite using Californian stamps, classifiers, sand and slimes tables, and circular buddles. Contamination was removed from the ore by the use of calciners and chemical treatment. Discharge from the refining process was treated in a tailings mill to recover the maximum amount of cassiterite from the effluent. All the structures are now roofless and all the machinery has been removed.

The tin processing works comprises three groups of buildings, being termed the western and eastern mills for the purposes of this scheduling. The third housed the tailings mill. The extant fabric of the buildings comprises low cement-rendered concrete block walls; the upper walls and roofs have been removed but were of corrugated steel sheets fixed to timber frames, internally supported on concrete piers. The floors inside the buildings are of screed concrete into which dipper-wheel pits and sunken channels have been created, the former to elevate process material to higher levels, and the latter to drain waste overflow from the processing plant for disposal. The works' buildings contain numerous concrete machine bases onto which sand and slimes tables and other processing machinery were fixed.

The ore dressing methods used in the works involved both gravity and chemical techniques. The western mill contained the primary ore dressing machinery which consisted of a Californian stamps battery and classifiers, with sand and slimes tables immediately in front. Chemical froth-flotation cells were in use in the western mill to remove contaminating arsenical sulphides from the processed ore. The eastern mill contained the secondary ore processing and calcining machinery and four cement-rendered circular convex buddles are positioned at the northern end. Two Brunton arsenic calciners are located at the southern end of the eastern mill. A pair of concrete coal chutes positioned at the rear of the calciners facilitated the delivery of fuel to the storage area there. A concrete and masonry arsenic flue connects the Brunton calciners to the arsenic scrubber chamber approximately 103m to the north east. The scrubber chamber was constructed to remove excess toxic gases from the calciner fumes by water treatment and is a reuse of a 19th century building. A short length of flue connects the scrubber chamber to a square concrete chimney immediately to the east.

The tailings mill, sited approximately 50m to the north of the eastern mill, screened the effluent from the latter to recover lost cassiterite. Constructed on two levels, it contains concrete machine bases, a dipper-wheel pit, and one visible cement-rendered circular convex buddle. Two parallel channels constructed using concrete blocks link the eastern mill to the tailings mill via a concrete settling tank. A sunken drainage channel curves downslope to the north from the western mill which was used for the disposal of process effluent at sea.

The St Agnes area was a significant producer of tin with rich deposits being worked during the 18th century. Prospecting pits, lode-back pits and openworks are extant in the area surrounding the tin processing works in addition to the shafts associated with deep lode mining.

MAP EXTRACT The site of the monument is shown on the attached map extract. It includes a 2 metre boundary around the archaeological features, considered to be essential for the monument's support and preservation.

Selected Sources

Books and journals
'The Mining Journal' in The Mining Journal, (1927)
Other
Adam Sharpe CAU, Personal comment on froth-flotation cells at Wheal Kitty mine, (2003)
Brooks, Personal comment on 20th century mining at Wheal Kitty, (2003)
Title: 1st Edition Ordnance Survey 1:2500 scale Map Source Date: 1880 Author: Publisher: Surveyor:
Title: 2nd Edition Ordnance Survey 1:2500 scale Map Source Date: 1907 Author: Publisher: Surveyor:

National Grid Reference: SW 72432 51415

Map

Map
© Crown Copyright and database right 2017. All rights reserved. Ordnance Survey Licence number 100024900.
© British Crown and SeaZone Solutions Limited 2017. All rights reserved. Licence number 102006.006.
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The above map is for quick reference purposes only and may not be to scale. For a copy of the full scale map, please see the attached PDF - 1021164 .pdf

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This copy shows the entry on 18-Nov-2017 at 02:40:38.

End of official listing