Cobscar calamine house on Cobscar Rake, 770m east of Cobscar Mill

Reasons for Designation

The zinc industry is defined as the mining and processing of zinc ores, and the smelting of these ores to produce metallic zinc. The former has a much longer history than the latter, since zinc ores were used for the production of brass for centuries before the smelting of metallic zinc was developed, and metallic zinc was not used on any large scale until the 19th century. Zinc ores are relatively common in the metalliferous orefields of England and normally occur in association with lead ores. The main primary ore is blende, however, close to the surface this has often been oxidised to produce calamine. Although zinc was known in the early classical world the possibility of prehistoric or Roman zinc mining and calamine processing in England is unproven. After this the technical skills involved in brassmaking appear to have been lost and brass was imported to England from the continent throughout the medieval period. In the 16th and 17th centuries there were repeated attempts to establish an English brass industry which in turn led to the development of a calamine-mining and calcining industry in the Mendips when calamine was discovered in 1566. This industry continued in the 18th century with some expansion into other areas. Further developments in smelting saw zinc metal (also known as spelter) being produced in England for the first time towards the mid-18th century, while the use of hot rolling to produce malleable zinc sheeting was developed at the start of the 19th century. At the same time more effective continental processes of zinc smelting were introduced into Britain improving the quality of metallic zinc, consequently the production of metallic zinc expanded from the Bristol area to Staffordshire and the North Pennines. The technology of zinc smelting became much more complex in the late 19th and 20th centuries as advances in roasting furnaces and smelting furnaces were developed. Attempts were also made to recover zinc from spoil heaps by fuming, whereby material was heated to vapourise the zinc content, which was then collected as zinc oxide `fume'. Sites specialising in this activity were known as fume works. Until the 19th century the only major end use for zinc was brassmaking, and this was produced from roasted calamine rather than from the metal. During the 19th century uses of zinc became much more varied; brassmaking remained a major consumer, and coating of iron and steel sheets (galvanised iron) was developed. Metallic zinc was increasingly used in the engineering and electrical industries and zinc oxide has been used as a white pigment in the paint industry. Calamine calcining houses were buildings in which the zinc carbonate ore was processed, primarily for use in the brass industry. Treatment undertaken here included calcination of crushed ore in furnaces to convert the zinc sulphide mineral to zinc oxide, and reduction of the oxide to metal using coal by heating of the charge held inside fire clay cylinders or retorts. The resultant zinc was a gas, which had to be condensed to liquid inside fire clay pipes stuck onto the retort mouths. This was one of the first stages in the brass making process and was usually undertaken at the mining area to reduce the weight of carriage to the brass works. In England up until the end of the 18th century calacination was usually done using wood fired reverberaratory furnaces. The use of calamine as the zinc source for brass making declined in the 19th century as the more accessible deposits were exhausted and more effective processes of zinc smelting were developed on the continent. The survival of smelt mills nationally is very poor with virtually all having been demolished. All sites with surviving field remains or good stratigraphic evidence are considered to merit protection. The bell pits included within the monument will retain evidence of lead mining and provide evidence of the date of the calamine processing and of its relationship with the lead industry. The remains of the calamine mill at Cobscar survive well and significant evidence of the technology involved in this aspect of the zinc industry will be preserved.

Details

The monument includes standing and buried remains of a calamine calcining house and waste tips located on the north side of Wensleydale, 2km north of Redmire. Also included are a number of bell pits associated with lead mining which are immediately adjacent to the calcining house. The monument lies within an area of open moorland within a wider lead and coal mining landscape. A calamine house is a building where zinc ore was processed, zinc minerals being found associated with lead in the nearby north Pennine orefields. Initially thought useless, zinc minerals were first used commercially in 1794 when zinc carbonate (calamine) began to be used in the brass industry. The calamine house was located on the western edge of an area of intensive lead exploitation centred on the Cobscar smeltmill lying 800m to the east. The calamine house was located here as there was a ready supply of fuel and zinc ore, which could be partly exploited using the existing technology of the lead industry. Lead was exploited commercially in the area from the mid-18th century and the calamine house has been dated to the late 18th century and early 19th century. The fortunes of the calamine house mirrored the lead industry which by the 1860s was in decline. There was a marked fall in the price of lead at the end of the 19th century and the industry did not survive that depression. The surviving remains demonstrate that the calamine house was a rectangular building measuring 6m by 5.5m with a door in the southern wall. Attached to the west wall was an open fronted structure 6 sq m. To the west of this is a cobbled yard measuring 11m by 13m. There is an entrance to the yard in the south eastern corner. To the south of the mill there are waste tips sloping away for 15m. There is a further 15 sq m spread of waste debris located to the east of the building ruin. There are the remains of a stone paved track way, 25m long, extending south from the eastern corner of the building mill to the track to the south. The rear (north) wall of the mill house survives to a height of 3.25m. The two side walls are partly collapsed and survive to a height of between 0.8m and 0.5m. The walls of the building and yard to the west survive as grassed over stone banks up to 0.5m in height. Cobbles forming the yard surface are exposed in places, as are some of the stone slabs forming the track way. The waste debris contains fuel slag and fragments of mineralised material. The lead mining bell pits lie at the southern side of the monument between the calcining house and the east to west track way which extends along the southern side of the monument. They are circular mounds of spoil surrounding a hollow that is the remains of a lead extraction pit. They are very closely spaced and measure up to 6m in diameter. The northern sides of the bell pits partly underlie the waste tips and thus will retain significant dating evidence of the relationship between the pits and the calamine processing. All fence posts are excluded from the scheduling, although the ground beneath these features 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.

Legacy

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

Legacy System number:

34827

Legacy System:

RSM

Sources

Books and journals
Raistrick, A, The Lead Industry of Swaledale and Wensleydale, (1975)
Dunham, K C, Wilson, A A, British Geological Survey in Geology of the Northern Pennine Orefield, Vol. VOL 2, (1985), 176

End of official list entry

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