Hallo.....the original point was whether "primary" cuprite would be
expected to be present, or could be present, in primitive copper smelting
processes from malachite, where prills of copper are produced at 800
degrees C, in the laboratory, which show some cuprite inclusions. Am I to
understand that the equilibrium conditions for the formation of fayalitic
slag with copper would preclude the appearance of cuprite in the copper
without further melting operations, but that, in cases where there is no
real slag produced, that the formation of "primary" cuprite in smelted
copper is still possible?
Have any of you noticed that the copper oxide formed from the probable
later melting operations is distinguished from other cuprite lumps by the
formation of a stationary cross under crossed polars (pseudo optical
indicatrix) ? I often find that this is the case with the little round
globules in early copper artefacts.....All the best...David
At 09:15 AM 3/26/2007 +0200, you wrote:
>I can not follow completely this series of arguments, because, after my
>opinion, they do not match the point.
>In our publication on Uluburun (Hauptmann et al., BASOR) we carefully
>pointed out the existence of tiny angular slag fragments (consisting of
>fay, hercynite-mt, glass) embedded in a matrix of copper (the material of
>the entire ingot)that contains Cu-Cu2O-eutectics and larger batches of
>Cu2O. The copper prills embedded in the tiny slag fragments are virtually
>free of oxygen. Taken all arguments together (please, follow our arguments
>in the publication!) we do not see any possibility to explain the texture
>and phase content other than with a two step process as explained.
>Definitely, fay is not compatible with cuprite. I never observed such a
>phase association in ancient slags.
>
>I am not convinced about Aaron Shugars fay + cuprite-pics in his
>dissertation. Please, could you send me such a sample? Not a picture, but
>a sample.
>
>Whatever the discussion is about equilibria in furnaces, I never doubt
>that there are equilibrium conditions in a crucible or in an ancient
>furnace, but inevitably the solidification of slags shows
>(micro-)equilibria (please, reade Hauptmann: Zur frühen Metallurgie des
>Kupfers in Fenan, Jordanien. Der Anschnitt, Beiheft, 2000 or, if you are
>have a littel patience, Hauptmann, The Archaeometallurgy of Copper:
>Evidence from Faynan, Jordan. Springer, Heidelberg- Berlin - New York).
>
>Prof. A. Hauptmann
>
>-----Ursprüngliche Nachricht-----
>Von: Arch-Metals Group [mailto:[log in to unmask]] Im Auftrag von
>[log in to unmask]
>Gesendet: Dienstag, 6. März 2007 15:01
>An: [log in to unmask]
>Betreff: Re: Cuprite in smelted copper
>
>The problem with all such arguments is the assumption of thermodynamic
>equilibrium. There are (at least) two schools of thought on this in
>archaeometallurgy. One, of which Andreas Hauptmann is a prominent
>exponent, uses equilibrium phase diagrams as the primary means of
>interpretation of chemical data. The other school, of which I am a member,
>tends to assume that in the very small reaction volumes that are typical
>of early metallurgy equilibrium is not usually achieved. This is
>especially true of slags, where it is very common to find
>thermodynamically incompatible minerals like quartz and fayalite in the
>same section. It is less common in smelted metals, but I have seen cuprite
>in primary smelted copper. My guess is that the atmosphere within small
>furnaces is quite variable, so that drops of copper metal may experience
>surface reoxidation while passing through a pocket with higher partial
>pressure of oxygen, and then be incorporated into the pool ofmolten copper
>at the furnace base, carrying the cuprite with it. If this is so then the
>distribution of cuprite within the copper might be expected to be in small
>patches, not evenly dispersed.
>
>Quoting David Scott <[log in to unmask]>:
>
> > Yes, one or two pictures would be good for comparison, Eugster and
> > Wones (1962)is the referecne which Hauptmann et al (2002) use for this
> > thermodynamic argument, and if you have even got cuprite in copper (in
> > the copper itself or only in the slag phase?) then where does that
> > leave the argument for the lack of cuprite in directly smelted copper?
> >
> > Quoting Aaron Shugar <[log in to unmask]>:
> >
> >> David,
> >>
> >> I have seen extensive cuprite growth in fayalitic smelting slag from
> >> the Chalcolithic Near East. Of course this is fairly basic copper
> >> smelting with limited superstructure furnaces so they were not very
> >> efficient, but I can send you a few pictures if you like.
> >>
> >> Aaron
> >>
> >>
> >>
> >> On 3/5/07, David Scott <[log in to unmask]> wrote:
> >>>
> >>>> Hallo All....I wanted to ask your opinion on the issue of cuprite
> >>>> inclusions in smelted copper....according to Hauptmann et al
> >>>> writing
> >>> about
> >>>> the copper oxhide ingots and tin ingots from the Uluburun (Sp?)
> >>>> shipwreck site they say, [contra Tylecote 1976] that we cannot have
> >>>> primary cuprite from the smelting of copper ores because the
> >>>> equilibrium conditions for the formation of a fayalite slag
> >>>> preclude the Cu/Cuprite eutectic being possible and that only in
> melting would one find that cuprite is present.
> >>>> In other words we can have primary cuprite, but only from melting
> >>>> of previously extracted copper, not from the smelting stage per se.
> >>>> But on examination of some experimental copper smelting from
> >>>> malachite at about 800 degrees C which would be pertinent for the
> >>>> Late or Final Neolithic of European copper smelting which I made
> several years ago, I find "primary"
> >>>> cuprite inclusions within the copper prills which were produced
> >>>> during this experiment. If these prills were then subsequently
> >>>> melted in a crucible, the copper may well pick up more oxygen, but
> >>>> we would still
> >>> have
> >>>> cuprite inclusions from the original smelt present. Now, the
> >>>> smelting conditions are not in equilibrium with a fayalitic slag of
> >>>> course at all, so does this invalidate the argument by Hauptmann et
> >>>> al and suggest that Tylecote was not entirely wrong? Can one
> >>>> always assume that the production of ox-hide (or other ingots)
> >>>> would have had to rely on smelted copper produced with the kind of
> slag associated with more "advanced"
> >>>> copper extraction processes rather than the remelting of small copper
> >>>> prills? Best wishes to all.....Professor David A. Scott.
> >>>
> >>>
> >>> Professor David A. Scott
> >>> Chair, UCLA/Getty Conservation Program The Cotsen Institute of
> >>> Archaeology, Room A410 University of California, Los Angeles
> >>> 405 Hilgard Avenue
> >>> Los Angeles, CA 90095
> >>>
> >>
> >>
> >>
> >> -- Aaron Shugar
> >> [log in to unmask]
> >> [log in to unmask]
> >> [log in to unmask]
>
>
>
>Prof. Dr. Andreas Hauptmann
>Forschungsleiter Archäometallurgie
>Telefon: +49 (234) 968 4041
>Fax: +49 (234) 968 4040
>E-Mail: [log in to unmask]
>Deutsches Bergbau-Museum
>Herner Straße 45
>44787 Bochum
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Professor David A. Scott
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The Cotsen Institute of Archaeology, Room A410
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