> In true lead mining this shift appears to correlate with the introduction
of roller crushing mills at the very end of the 18th century.  In the 13th
century, therefore, they were presumably using hammers and/or stamps before
getting a product small enough to treat in a crazing mill.  There would also
(presumably) be intermediate sorting processes, using sieves and/or buddles.

Mike,

In the late 13th/ early 14th century Devon mines they do not appear to have
been using crazing mills in the processing of silver-bearing ores -
certainly there is no documentary evidence and, as no archaeological
investigations have yet been carried out, there is no field evidence. What
archaeological evidence we do have is for Lyonaise mines in the mid 15th
century. But the documentary evidence in Devon points to a situation where
the crazing mill or stamps might have been beneficial to the process.
Bucking hammers and edge wheels for crushing (although the latter were
confined to crushing smelting residues), sieves and washing places, i.e.
buddling sites, are documented, and the smelting technique used points to
the processing of crushed ore, which leads into your second point -

>> The use of furnace smelting with higher temperatures and a reducing
atmosphere >Galena is a sulphide and needs to be at least partly oxidised
before it can be smelted.  Could this be done in the furnaces you refer too?

The use of the bellows blown, charcoal fired furnace would certainly result
in the loss of some lead through volatilisation but that was acceptable when
the object of the process was the silver. When, in the 15th century, all the
ore from the Devon mines was smelted in water powered furnaces then
preliminary roasting is documented but, with a combination of bole and
furnace in use, there was always partially oxidised residues from the former
to add to the furnace charge. In fact the delay of three years, between the
opening of the Devon mines and 1295, in introducing furnace smelting might
be put down to a need to accumulate 'blackwork' residues to initiate the
reaction in the furnace.

We should look at innovations in ore processing (preparation and smelting)
in terms of resource depletion. Development of roller crushing mills, ore
hearth smelting, the flotation process; they can all be explained as moves
to make more of the available resources.

As I said in an earlier message, the mining of silver-bearing ores reach
that crisis at an earlier stage than non-argentiferous lead mining. However,
and again I've probably mentioned this before, the ore hearth appears to
have been born of resource depletion in the English non-argentiferous sector
on Mendip and quickly spread to other mining fields in the late 16th
century. But the appearance of the 'blackwork furnace', for treating
smelting residues, in Co. Durham in the 15th century and the presence of
'lead ore sand', i.e. crushed galena, amongst the assets listed in some
early 16th century Swaledale (Yorkshire) wills suggest that position had
been reached long before the introduction of the ore hearth.

But to return to your specific points -

I have no specific detail on the ores in the Devon silver mines of the late
13th /early 14th century, although both galena and cerussite were worked,
but the techniques documented suggest they were mixed with significant
amounts of gangue material.

As to the archaeology, that is the next stage in investigating the Devon
mines - my own work has identified many aspects of mining which cannot not
be satisfactorily explained by the surviving documentation plus some
physical features which supported the documentary evidence but require
further investigation.

As to bashing the French and Spanish - primarily the latter from the 16th c.
onwards, before that they were in the same position as the English, trying
to extract the last ounce of silver from indigenous resources or relying on
central European production. Suprisingly, however, robbing others of their
monetary resources was not the panacea it might seem - the most productive
phase of English / Welsh silver production since the 12th century came in
the late 16th and early 17th centuries!

This is certainly a discussion which can be expanded beyond the medieval
period, non-ferrous metal mining and the UK.

Peter

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Dr Peter Claughton,
Blaenpant Morfil, nr. Rosebush, Clynderwen, Pembrokeshire, Wales  SA66 7RE.
Tel. 01437 532578; Fax. 01437 532921; Mobile 07831 427599

University of Exeter - School of Historical, Political and Sociological Studies
(Centre for South Western Historical Studies)
E-mail:  [log in to unmask]

Co-owner - mining-history e-mail discussion list.
See http://www.jiscmail.ac.uk/files/mining-history/  for details.

Mining History Pages - http://www.exeter.ac.uk/~pfclaugh/mhinf/

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