Blackaton Ball tin mill

Summary

Tin mill 290m east of Grendon.

Reasons for Designation

Dartmoor is the largest expanse of open moorland in southern Britain and, because of exceptional conditions of preservation, it is also one of the most complete examples of an upland relict landscape in the whole country. The great wealth and diversity of archaeological remains provide direct evidence for human exploitation of the Moor from the early prehistoric period onwards. The well-preserved and often visible relationship between settlement sites, major land boundaries, trackways, ceremonial and funerary monuments as well as later industrial remains, gives significant insights into successive changes in the pattern of land use through time. Blowing mills (also known as blowing houses) survive as rectangular drystone buildings served by one or more leats and are characterised by the presence of granite blocks with moulds cut into them - mould stones - and on occasion by the square or rectangular stone built base of the furnace itself. During the medieval and early post-medieval period, black tin (cassiterite) extracted from streamworks and mines, was taken to blowing mills to be smelted. During the same period tin ore was taken to stamping mills to be crushed, using heavy iron-shod stamps attached to the lower end of vertical wooden posts called lifters, which were raised using a water-driven rotating axle. Thus raised, the stamps fell under gravity onto the ore, crushing it between the stamp's head and a hard slab of rock called the mortar stone. There were two types of stamping machinery. The first, known as dry stamps, involved the crushing of the ore without use of water, and appears to have been employed throughout much of the medieval period until the introduction of wet stamping in the 16th century. Wet stamping utilised a constant flow of water to carry the tin crushed by the stamps through a fine grate into a channel, to be carried in suspension to a settling pit from where it could be collected for dressing. Dressing involved separating the lighter waste minerals from the heavier cassiterite (tin oxide) using water. Much of this work was carried out in sloping rectangular or triangular shaped boxes called buddles where, to prevent premature sedimentation, shovels were used to agitate the contents. The original number of stamping mills on Dartmoor is unknown, but at least 60 survive. Those with associated dressing floors are relatively rare. Despite invasive scrub growth and some animal burrowing the tin mill 290m east of Grendon survives comparatively well and traces of the associated dressing floors still visible on the ground give additional importance. The documentary evidence relating to this site also adds to its interest and suggests it was a stamping mill, but since both blowing and stamping could be carried out in the same building and it has also been referred to as a blowing mill the more generic tin mill is applicable. The mill will contain archaeological, environmental and chemical evidence relating to its construction, function, longevity, the competence of the work force and the sources of the tin ore. All tin processing sites are restricted in Britain to Devon and Cornwall.

History

See Details.

Details

This record was the subject of a minor enhancement on 18 November 2015. This record has been generated from an "old county number" (OCN) scheduling record. These are monuments that were not reviewed under the Monuments Protection Programme and are some of our oldest designation records.

This monument includes a tin mill with dressing floor situated close to the source of the west Webburn River. The mill survives as a largely buried structure with slight earthworks and traces of masonry walls visible above ground. The building is rectangular with a wheel pit which is approached from the north by a substantial leat with a tailrace leading back to the river. To the south of the mill there are traces of further channels and pits which probably represent the buried features associated with a tin dressing floor. Documentary evidence indicates the existence of a stamping mill at ‘Blackaton Ball’ prior to 1556.

Legacy

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

Legacy System number:

DV 1028

Legacy System:

RSM - OCN

Sources

Other
PastScape Monument No:-442487

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