To elaborate on what Peter Northover says in his remarks on metallography of
gold, I add that if the metallography is aimed at determining what effect
mechanical operations had or has on the grain structure, it would be wise to
remember that gold (depending upon the amount and nature of the impurities)
recrystallizes at room temperature. Hence, what you observe need not
represent what you would wish to conclude. Such, I believe, is the case in
the Eleure/Raub study where extensive hammering into foil must have effected
the structures reported.
Deterring porosity and inclusions, used, for example, by Young in attempting
to the 'source' the gold can readily be done by microscopic (optical and
electron microscopic examination) in the unetched condition. Indeed,
C.S.Smith used very low power (~x5) to study and determine the nature and
distribution of inclusions on the Ur cup now on exhibit with the Ur
treasures.
The major problem in studying the metallography of gold is really getting
permission from the museum curator to part with a piece large enough to
meaningful in any metallographic context.
R. Maddin
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