Reasons for Designation
Approximately 10,000 lead industry sites are estimated to survive in England,
spanning nearly three millennia of mining history from the later Bronze Age
(c.1000 BC) until the present day, though before the Roman period it is likely
to have been on a small scale. Two hundred and fifty one lead industry sites,
representing approximately 2.5% of the estimated national archaeological
resource for the industry, have been identified as being of national
importance. This selection of nationally important monuments, compiled and
assessed through a comprehensive survey of the lead industry, is designed to
represent the industry's chronological depth, technological breadth and
regional diversity.
The ore works were an essential part of a lead mining site, where the mixture
of ore and waste rock extracted from the ground were separated (`dressed') to
form a smeltable concentrate. The range of processes used can be summarised
as: picking out of clean lumps of ore and waste; breaking down of lumps to
smaller size (either by manual hammering or by mechanical crushing); sorting
of broken material by size; separation of gravel sized material by shaking on
a sieve in a tub of water (`jigging'); and separation of finer material by
washing away the lighter waste in a current of water (`buddling').
The field remains of ore works include the remains of crushing devices,
separating structures and tanks, tips of distinctive waste from the various
processes, together with associated water supply and power installations, such
as wheel pits and, more rarely, steam engine houses.
Simple ore dressing devices had been developed by the 16th century, but the
large majority of separate ore works sites date from the 18th and 19th
centuries, during which period the technology used evolved rapidly.
Ore works represent an essential stage in the production of metallic lead, an
industry in which Britain was a world leader in the 18th and 19th centuries.
Sites are common in all lead mining areas and a sample of the best preserved
sites (covering the regional, chronological, and typological variety of the
class) will merit protection.
The remains of Slack, Mount Pleasant and Barmasters Grove lead mines 390m
south east of Blakelow Farm are well preserved and include a number of
components relating to the mining of these veins. They have particularly early
origins and will retain significant information about early lead working. The
standing, earthwork, buried and rock cut remains combined with the documentary
sources provide evidence for both the historical and technological development
of what was once a far more extensive, multi-period mining landscape. They
incorporate a wide range of mining and processing features, which enable the
development of the mine working and its chronological range to be
reconstructed. The large veins, smaller scrins, shafts, hillocks and other
extraction features provide evidence for methods of extraction whilst other
processing areas will contain deposits showing the effectiveness of these
techniques. The mining remains also provide an insight into the Derbyshire
Barmote Court system of mining and the constraints this imposed on the miners
of the area.
Details
The monument includes the earthwork, buried, standing and rock cut remains of
Slack, Mount Pleasant and Barmasters Grove lead mines 390m south east of
Blakelow Farm. The monument is situated on Bonsall Moor, between Bonsall Lane
and Tower Lane. Geologically, the monument lies to the north of the Great
Bonsall Fault, with the lead veins running through gently folded limestone and
lying at a stratigraphic horizon beneath the Matlock Lower Lava.
Ore accounts dating from 1541 provide the earliest record of mining on Bonsall
Moor but most of the surviving surface remains represent mining activity of
the 18th and 19th centuries. In 1881 Slack Mine and the adjacent mines were
bought by Edward Wass who in the following year had his agent, Jonathon
Stevenson, examine the New Shaft at the mine. This examination revealed water
at a depth of 222 feet (67.6m). As a result it was proposed to extend the 18th
century Dalefield sough (a level driven primarily for drainage), over a
distance of 800 yards (732m) to the mine. Although this was started, the task
was never completed due to financial constraints.
The mines would have been worked under the jurisdiction of the Barmote Courts,
the legal administrative unit governing Derbyshire lead mining. The Derbyshire
system of mining was largely based on local mining customs and consisted of
individual groups of miners or small mining companies working relatively short
lengths of the vein.
The monument survives as a series of earthwork, buried, standing and rock cut
remains which include several almost parallel veins and scrins. These are
aligned roughly north to south and are marked by a series of hillocks (mounds
of waste rock which either contain insufficient quantities of ore to warrant
extraction, or waste from ore crushing activity) interspersed with the remains
of mining shafts and open cuts (veins worked open to daylight).
Slack Mine, which includes Nether Slack, Upper Slack and Scorah Slack, is
situated on two parallel veins. At the northern end of the monument, in the
area of Nether Slack, is a shaft which was documented in the late 18th century
as being 50 fathoms deep. This has now partly collapsed but sits adjacent to
a retaining wall and a coe, close to Bonsall Lane. Close to these remains is
an ore processing area including a water channel and a buddling area where
water was used to separate small sized ore from adhering dirt.
Towards the southern end of the monument, in the vicinity of Scorah Slack, is
a large shaft surrounded by a substantial coe with retaining walls. Similar
remains characterise Mount Pleasant and Barmasters Grove mines which are
situated in the eastern half of the protected area. Within the easternmost
field are the remains of at least ten open shafts scattered along the lines of
hillocks, hollows and deep open pit holes which mark the line of the lead
veins.
The individual mines are not marked by concentrated areas of activity but
instead relate to stretches of the vein which were worked by different miners
or groups of miners, a characteristic of the Derbyshire lead mining custom.
All modern fences, gates and stiles 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.
