Dear Paul,
Copper ore analyses can be somewhat unhelpful when trying to connect
metal to mineral even on a site where the whole process is present. It
is necessary to check precisely what is being analysed. Some of the
relevant copper minerals (e.g. chalcopyrite, chalcocite) contain very
low levels of many trace elements because solid solubility of those
elements in the mineral is very limited. While there are minerals
which contain both copper and nickel it is more probable that high
levels of nickel (and other elements as well) come from other minerals
intimately associated with the copper mineral so that they are smelted
together. It is also possible that a mix of minerals was deliberately
smelted: there are Old World examples where it is probable that this
was done to enhance arsenic and lead contents, while the paktong of SE
Asia and China was made from a deliberately selected Cu/Ni ore.
Even when there is nickel in the ore it may not end up in the copper.
At the Chalcolithic site of Almizaraque in Spain the ore is often in
the form of pieces of azurite cemented with arsenates, nickelates
etc., but while an arsenical copper was produced in a crucible smelt
the nickel appears to segregated to a speiss phase which tended to
remain trapped in the slagged interior of the crucible.
For your South American example you must look at the relevant
mineralogy as a whole and not just the copper minerals. I am sure
there are other list members who have suitable knowledge of the area.
By the way, for a good overview of the whole range of pre-Columbian
metals and alloys in South America you should consult Salvador
Rovira's thesis, centred round a comprehensive analysis of the
collections of the Museo de America in Madrid. Salvador's e-mail is
[log in to unmask] and he should be able to help you lay your hands on a copy.
Yours,
Peter Northover
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Peter Northover
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