There are certainly literary references to brass before the 4th century BC - Plato gives the Atlanteans quite a lot of brass, as I recall, and Stesichoros and Bacchylides both refer to it. But it is not certain that this was zinc brass - it might have been a Cu-Sb alloy. In the last century a small quantity of natural Cu5Sb was found on Lesbos. Unfortunately, a very prominent American university managed to lose the type specimen! But it seems plausible that there were small deposits of Sb rich natural Cu in the medterranean world which were mined out over the years. I have no personal experience of Cu-Sb alloys, but when I was studying natural corrosion products I was frustrated by the tendency of Zn brass both to corrode and to dealloy. The rarity of Zn brass artifacts is exaggerated by this tendency. I have a Roman coin of which 2 cm of the outer surface is completely depleted of Zn - if this had been any other type of artifact, I would probably not have felt fre to cut it & would still think it was entirely Cu.
>>> [log in to unmask] 11/30 7:33 AM >>>
In respionse to various threads.
Besides the zinc plate from the Athenian Agora there is a very small
number of pieces of zinc metal from apparently Roman contexts. I have a
report from Thilo Rehren, then at the Bergbau Museum in Bochum on "A
Roman zinc tabula from Bern, Switzerland: reconstructing the
manufacture". A piece of zinc was found during the excavation of a 1st
century AD cremation burial at Folly Lane, St Albans, UK. Not all the
metal recovered had been through the pyre and it is quite reasonable
stratigraphically that the zinc is Roman. However, there were signs of
disturbance in the vicinity which have been C14 dated and can be
attributed to a medieval squirrel burying nuts.
Before the introduction of brass the use of zinc-rich ores for smelting
copper happened in anumber of places, probaly the earliest being in the
Early Bronze Age of central Italy, around the begining of the 2nd
millennium BC. Zinc contents can exceed 5%. A source on the Welsh
border was producing copper containing zinc in the 3rd-1st centuries
BC; the raw copper ranges up to 4% zinc. As more and more metalwork
from Anatolia and the ancient Near East is analysed copper alloys
containing zinc are more and more frequently observed. Thus the emtal
which is often cited as the first real brass, from Taxila in about the
4th century BC, seems a natural outcome of previous developments.
On the subject of cooking pots, in medieval Britain at least, they
would be mainly ceramic with some cast copper alloy pots. By about the
fourteenth century these alloys could have several percent of arsenic
and antimony in and be heavily leaded as well - most unsuitable for
cooking.
On the subject of mercury gilding (as opposed to mercury itself) Ordos
plaques from NW China in about the 4th century BC still seem to be the
earliest examples of mercury gilding. The earliest dated examples in
the west are in the Senttisham Late Iron Age treasure from Norfolk UK.
These probably date around 50BC.
If people need references for some of this I can supply them in due
course - no time to look them up at the moment.
Peter
-------------------
Dr Peter Northover,
Materials Science-Based Archaeology Group,
Dept. of Materials, University of Oxford,
Begbroke Business and Science Park,
Sandy Lane,
Yarnton,
Oxford, OX5 1PF
Tel. 01865 283721; Fax. 01865 841943; Mobile 07785 501745
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