Trevor,
Sorry about the slow reply. I have had a further look at at your slag,
and can confirm without a doubt that it is copper smelting slag. There
are copper metal and copper sulphide prills in the slag. The copper is
saturated with iron but there are no separate metallic iron inclusions.
The slag samples I have looked at mostly were very rapidly cooled -
consistent with thin tap slag flows. The primary dendrite material seems
to be fayalite - but there are various complications in the structure
that need to be investigated. Unfortunately, I have not had time to
compile a proper report or even process the second set of data. But it
does not to be similar to copper slags from 18th and 19th century
Swansea, I will have to go back and check if they are similar to the BA
material from Schrane, Ireland which I have completely forgotten what
they look like on the microscopic scale - but certainly were
macroscopically different as those were platey slags formed on top of
liquid copper or matte.
As I am sure you have worked out for yourself, unless these were
brought in from Swansea or Hayle as ballast (very very unlikely on an
inland site), this material is very important no matter what the date
(19th century or earlier).
--
Chris Salter,
Oxford Materials Characterisation Service,
&
Material Science-based Archaeology Group,
&
Electron Microscopy Research Support Group,
Oxford University Begbroke Science Park,
Sandy Lane, Yarnton, Oxford, OX5 1PF
Tel 01865 283722, EPMA 283741, Mobile 07776031608
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