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.
