Early post-medieval tin streamwork at Gonamena


Heritage Category: Scheduled Monument

List Entry Number: 1020051

Date first listed: 11-Dec-2001


Ordnance survey map of Early post-medieval tin streamwork at Gonamena
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The building or site itself may lie within the boundary of more than one authority.

District: Cornwall (Unitary Authority)

Parish: St. Cleer

National Grid Reference: SX 26569 70801


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

Reasons for Designation

Bodmin Moor, the largest of the Cornish granite uplands, has long been recognised to have exceptional preservation of archaeological remains. The Moor has been the subject of detailed archaeological survey and is one of the best recorded upland landscapes in England. The extensive relict landscapes of prehistoric, medieval and post-medieval date provide direct evidence for human exploitation of the Moor from the earliest prehistoric period onwards. The well-preserved and often visible relationship between settlement sites, field systems, ceremonial and funerary monuments as well as later industrial remains provides significant insights into successive changes in the pattern of land use through time.

Streamworking formed one of the chief methods of mining throughout the history of the tin industry, and was the predominant method before the 17th century. The method used the high specific gravity of tin ore, cassiterite, to separate it from surrounding `waste' such as other minerals, earth and grits. It involved diverting and channelling a water supply across the ground to be worked, carefully controlling its speed of flow to remove waste material while retaining the tin ore. The ore-bearing ground was put into the channel for separating, usually from the upstream or upslope side. The tin ore and larger grits left behind were dug from the channel floor for secondary ore-dressing nearby, while larger rubble was dug out and heaped along the channel's downslope side, creating a linear spoil mound. Once a channel became too wide to control the speed of water flow, the rubble soil was used to define a new one, and so the streamworking advanced upstream or upslope until there was no further ore-bearing ground that was economical to work. The end result of streamworking is a broad steep-sided gully from which an often considerable volume of waste material has been removed; in the floor of the gully, various patterns of linear rubble dumps reveal the method and sequence of working, with the earlier dumps sometimes masked beneath silts washed down from the later working. Outside the streamwork gully may be leats and reservoirs which served its water supply. Streamworking was applied to two types of ore-bearing deposit, both separated from the parent lodes by weathering. In alluvial deposits, tin ore accumulated with other eroded materials in valley floors, becoming partly concentrated by natural sorting in the water-rich environment. Here the valley floor stream provided the water supply necessary from streamworking. In elluvial deposits, tin ore occurs in more poorly sorted subsoils weathered directly over the parent lodes, or on slopes and in hollows down which they have drifted under gravity and subsoil slumping. Exploitation of these by streamworking often required a considerable catchment area, and used leats and small reservoirs. Streamworks provide our main source of evidence for the methods employed in tin mining and its scale in the landscape during the early and post-medieval periods, aspects for which historical documentation is scanty and inadequate. The elluvial streamwork at Gonamena has survived well. It retains a good range of features, of which some; the north-south channel, its dumps, leat and reservoirs, demonstrate the basic methods of streamworking while others; the prospecting pits, the eastern extension, its reservoir, water course and relationship with the earlier dams, clearly illustrate the development and changes in the streamwork through time. The streamwork contains one of the broadest and deepest of known streamwork gullies and is unusual in combining two such complementary gullies, working elluvial deposits in the hollow and over the adjacent lode itself. Further details of the streamwork's earlier phase working will be preserved beneath the later silts on the floor of its southern sector.


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


The monument includes an early post-medieval tin mine, of a type called a streamwork, near Gonamena on the lower western slopes of Caradon Hill on south eastern Bodmin Moor. The Gonamena streamwork is visible as a large and deep gully which, overall, extends along roughly 800m of the lower western flank of Caradon Hill. It results from the exploitation of tin ore, cassiterite, which had been detached from its parent lodes by weathering to form an elluvial deposit both overlying the lodes and accumulated in a slight trough north east of the hamlet of Gonamena. The methods used to extract the ore involved careful manipulation of water to flush away unwanted soil, clays and grits, leaving behind the heavier tin ore. The resulting physical remains include: a deep channel along the course of the former elluvial deposit, from which the tin ore has been removed and considerable quantities of waste material have been washed away; dumps of the larger waste rubble in the channel floor which also directed the water used to work the ground immediately upslope; and remains of water-courses, called leats, and reservoirs which brought and concentrated water to operate the streamwork. The Gonamena streamwork combines two main elements: a north-south channel extending 675m, following the elluvial deposit in the trough along the hill's western foot, and an eastward extension from the north of that channel, which tapers in width and depth over its 260m length to follow elluvial deposits over the parent lodes and possibly exploit upper levels of the lodes themselves by cutting an open trench along them, called a stockwork. The north-south channel is considered to have formed the initial phase of the streamwork, during which the lodes underlying the eastern extension will have been revealed. The channel has a gentle `S'-curve and ranges generally from 40m to 70m wide, its steep sides descending up to 16m to the streamwork floor. A stream runs roughly centrally along the floor, meandering around remains of dumps and modifying their surface expression by silting. Where surface scrub and later deposits allow inspection, traces of linear dumps are visible, about 2m wide and 0.25m high, lying at an angle to the streamwork's long axis and with their downstream ends towards the centre of the channel. The southernmost 185m of the channel has been modified and narrowed by the intrusion into its western side of revetted dumps and a finger dump, beyond this scheduling, from the mid- to later 19th century Gonamena Mine. North of those dumps and within this scheduling, further spoil from that later mine forms a rubble spread over the west of the streamwork floor. The eastward extension of the streamwork tapers from 140m wide and 16m deep on the west side where it meets the north-south channel, to a rounded eastern tip 10m wide and about 4m deep. The sides of the eastern extension drop steeply to the floor which here contains a pattern of linear dumps, some over 1m high, both parallel with and angled to the long axis of the extension. Terraced out from the extension's northern slope, near its junction with the north-south channel, is a rounded reservoir up to 25m across, which is considered to have served an ore-processing area on the streamwork floor below after streamworking had progressed eastward past this point. Another later feature which may have supplied water for ore-dressing on the floor is a narrow leat which originates against the northern side of the extension near its upper end, cutting through several dumps along its course and revetted variously by coursed rubble and edge-set slabs. Beyond the northern edge of the streamwork are several closely related or later features. Extending at least 135m north west from the northern end of the north-south channel is a leat, now dry, which directed water to the streamwork; the final 35m of the leat beside the head of the streamwork may have been modified by the ditch of a post-medieval hedgebank. A small upright slab within that hedgebank ditch as it descends into the head of the streamwork may be a post-medieval common land boundary-marker. Around the head of the streamwork's north-south channel is a dense scatter of prospecting pits used for seeking underlying lodes after the end of work on the streamwork channel. The pits, 1m-6m across, 0.2m-2m deep and linked by their spoil heaps, occupy a well-defined zone 20m-40m wide around the upper end of the streamwork. Towards the east of the eastern extension, its northern crest crosses a group of three closely-spaced and parallel dams whose earthen banks extend 20m-50m to the north, each with a slightly sunken reservoir hollow 3m- 4m wide behind the dam and two with clear central breaks which formerly held sluice gates. Their truncation by the streamwork extension rendered them useless in their original form and confirms their earlier date, most probably to store water to work the north-south channel. However after truncation they were modified by a bank linking the western two dams behind the crest of the extension's scarp, forming a smaller reservoir contemporary with the extension. Only 40m beyond the southern end of this monument, the upper valley of the River Seaton contains a broadly contemporary streamwork exploiting the alluvial concentration of tin ore along the valley floor, though much of that has been disturbed or overdumped by the spoil and processing areas of the intensive 19th century mining in the vicinity. Working of this monument is likely to have begun during the medieval period but its earliest documentary reference relates to the `tynworks' at Gonamena in 1662, and, in 1690, to the `Gunnamanna streamworks' and the `Mill Bounds', all now called `Gunnamanna new pitched'. Exploitation may have continued into the 18th century but had ceased by the 19th century, the streamwork being depicted to its present extent on the earliest Ordnance Survey drawings of 1805. The electricity supply cables and their poles, all modern gates, fences and the surface of the embanked track across the south of the streamwork 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. It includes a 2 metre boundary around the archaeological features, considered to be essential for the monument's support and preservation.


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

Legacy System number: 15554

Legacy System: RSM


Books and journals
Sharpe, A, The Minions Area Archaeological and Management Survey, (1993), 84-6
Sharpe, A, The Minions Area Archaeological and Management Survey, (1993), 84-6
Sharpe, A, The Minions Area Archaeological and Management Survey, (1993), 267-270
Sharpe, A, The Minions Area Archaeological and Management Survey, (1993), 87-91
Sharpe, A, The Minions Area Archaeological and Management Survey, (1993), 84-6
Title: 1:10000 Ordnance Survey Map SX 27 SE Source Date: 1983 Author: Publisher: Surveyor:
Title: 1st Edition 25": 1 mile Ordnance Survey Map covering Gonamena area Source Date: 1880 Author: Publisher: Surveyor: As appnd to Step 3 Assmt Tin CO 129
Title: 1st Edition 25": 1 mile Ordnance Survey Map covering west of Caradon Hill Source Date: 1880 Author: Publisher: Surveyor: Appnd to Step 3 Site Assmt Tin CO 129
Title: 25": 1 mile Ordnance Survey Map Cornwall sheet XXVIII: 10 Source Date: 1883 Author: Publisher: Surveyor:
Title: Ordnance Survey 25": 1 mile Map Cornwall sheet XXVIII:10 Source Date: Author: Publisher: Surveyor: 1883 1st Edn and 1906 2nd Edn

End of official listing