THE EARLIEST COPPER METALLURGY IN NORTHERN ITALY

Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2009-2010
THE EARLIEST COPPER METALLURGY IN NORTHERN ITALY: STUDY OF COPPER
SMELTING SLAGS OF ENEOLITHIC AND BRONZE AGE
Ph.D. candidate: ANNA ADDIS
Tutor: Prof. GILBERTO ARTIOLI
Co-tutor: Dott.ssa IVANA ANGELINI
Cycle:XXV
Abstract
The Eneolithic copper smelting in Italy and its progress in the Early Bronze Age are a hot topics for debate. Relevant research
on copper smelting slags showed that the use of different smelting technologies result in a different reaction advancement and
in copper extraction efficiency. This in turn is recorded in the mineralogy of the slags. In order to describe these phases,
several copper smelting slags from Trentino area were investigated by using XRPD and optical microscopy. Multivariate
statistical analysis on the samples was also performed using the physical parameters as observables. This first stage of the
doctorate project aims to define the metallurgical process that characterized the earliest metallurgic activity of copper in
Northern Italy and its time evolution. Besides, archaeometallurgical copper smelting experiment conducted in Agordo in
collaboration with ARCA (Gruppo Archeologico Agordino) are presented as an attempt to better understand the primitive
smelting processes. The sampling, preparation and preliminary analysis of Pb isotopes of copper slags and minerals carried
out at the University of Bern are described.
Introduction
The origin and development of the extractive copper metallurgy in Italy is one of the most actively argued
matters in prehistoric archaeology. The evidence for the first steps of the smelting process is very difficult
to document, both in the surviving early metal and in the smelting remains. Though there is evidence of
copper objects from the Late Neolithic (second half of 5th millennium B.C.) in Central Europe and in the
Alpine area (Artioli et al., 2007), a complete correlation between mining as well as smelting sites, metal
workshops and object distribution areas is lacking. Hence this research investigates earliest copper Italian
metallurgy, involving integrated approaches for understanding every field of the metallurgical chaîne
opératoire.
The archaeometallurgy cycle (after Ottaway 1994)
The metallurgical activities start at the ore deposit with ore extraction and enrichment followed by
technological steps of the smelting processes, producing raw metal and other intermediate products like
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Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2009-2010
metallurgical slags (Hauptmann, 2007). Since a smelting process from sulphides is always connected with
production of slags and because slags are often the only witnesses of archaeometallurgical processes
(Bachmann, 1982), their characterization constitute a relevant issue of archaeometallurgical research.
Slag analyses provide substantial information about applied processes and their conditions, such as
temperatures, red-ox condition, viscosity, efficiency of smelting, provenience of charge component and
different steps in metal production. Regarding this latter point various slag features from many
archaeological sites in Italy dating from Eneolithic to Late Bronze Age, suggest a different levels of
copper smelting resulting in distinct degrees of reaction advancement and copper extraction efficiency
(Artioli et al., 2007). This fact requires further analysis of the various parameters responsible for these
different types of slag and their technical as well as archaeological interpretation.
The aim of the present project is to understand the metallurgical processes that characterize the earliest
copper smelting in Italy (Eneolithic Age) and their progress into Bronze Age technologies, by chemical
and physical analysis of several Italian Eneolithic and Bronze Age smelting copper slags.
Samples, Methods and Activities of the first year
The first steps of my research focused on:
•
The study of smelting slags from three archaeological sites of the Trentino area dated to Late
Bronze Age: 1400-1000 B.C. (Bellintani et al., 2009). Already 187 slag samples from the Luserna,
Segonzano and Transacqua sites were preliminary analysed for macroscopic features (colour,
texture, sides, thickness, weight, presence/absence of quartz, copper oxide, iron oxide, charcoal,
voids) and separated into morphological types. Based on the macroscopic features and in
agreement with archaeological arguments, eight different types have been highlighted, besides the
two common Late Final Bronze Age classes: coarse/cake slags (grossolane): typically at least a
few cm in size, frequently forming irregular or subrounded slag cakes and flat Plattenschlacketype slag (piatte), having a rather constant thickness of about 1 cm or less. The new established
six typological classes are: piatte-spesse, piatte-rugose, piatte-spesse-rugose, massive, grossolane
massive, fluide. These six types can be considered as a mix of coarse, flat and “massive” slags. For
each slag the density has been calculated and statistical analysis has been performed to examine
the correlation between macroscopic cluster types and densities. Then, part of them were analysed
by X-Ray powder diffraction (XRPD) and optical microscopy. The purpose of these investigations
is the determination of the level of metallurgical technology. Particularly we mind the
technological advancement of the processes performed, the copper extraction efficiency in the
three sites and the presence of different steps in metal production. These aspects are based on the
results of statistical analysis of density, the XRPD results, and the textural and chemical analyses
by optical microscopy and electron microscopy (SEM_EDS).
•
Copper smelting experiments were performed in collaboration with “ARCA: Gruppo
Archeologico Agordino”. We carried out eight smelting experiments (starting from chalcopyrite
and malachite) and one roasting experiment. Three different types of chalcopyrite were used with
different degrees of roasting, and two different types of malachite. We used an artificial air source
and carbon cake to feed the combustion, resulting in temperatures high enough to extract metals
from the ore. Experimental smelts have shown that there is no problem in smelting copper from
high-grade malachite ore, but only a few experiments provided copper from copper-iron
sulphides. Thorough sampling of metal and slag produced by these experiments have been carried
out.
These experiments aim to investigate the degree of copper smelting efficiency with different
starting materials, and the contribution of the charge component in the lead ratio analysis of the
products. Traces of lead incorporated in ores and metal artefacts may have specific lead isotopic
signatures that vary from one ore deposit to the other. Lead isotopic ratios have been used for a
long time to identify provenance areas of ore. In the case of slags, there can be different
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Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2009-2010
contribution to the isotopic signal from the distinct components of the charge which makes their
interpretation difficult.
•
Pb isotopes. We carried out sampling of slags and minerals for lead isotopic analyses at the
University of Bern. In the ultra-clean laboratory there, we dissolved slag samples with nitrohydrochloric acid. It is necessary to chemically remove all elements except Pb, as the
measurement accuracy depends on the purity of lead (Villa, 2009). This is normally done with
cation or anion exchange resins, which retain or release specific elements with specific acids of
specific concentration. The last step is to analyse them by Multicollector ICP-MS to determine
lead isotopic ratios ( Pb/ Pb, Pb/ Pb, Pb/ Pb). At present a multivariate statistical analysis is
in progress.
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References
ARTIOLI, G. ANGELINI, I., BURGER, E., BOURGARIT, D. 2007. Petrographic and chemical
investigation of the earliest copper smelting slags in Italy: towards a reconstructions of the beginning of
copper metallurgy. Proc. 2nd Intern. Conference “Archaeometallurgy in Europe 2007, Aquileia, 17-21
June 2007. Proceedings on CD.
BACHMANN, H. G. 1982. The identification of slag from archaeological sites. Occasional Pubblication
No.6. Published by the Institute of Archaeology, 31-34 Gordon Square, London, WC1H 0PY.
BELLINTANI, P., MOTTES, E., NICOLIS, F., SILVESTRI, E., STEFAN, L., BASSETTI, M.,
DEGASPERI, N., CAPPELLOZZA, N. 2009. New evidence of archaeometallurgical activities during the
Bronze Age in Trentino. Proceedings for the 1st Mining in European History-Conference of the SFBHIMAT, 12.–15. November 2009, Innsbruck.
BOURGARIT, D. 2007. Chalcolithic copper smelting, in S. LaNiece, D. Hook & P. Craddock (ed.)
Metals and mining: studies in archaeometallurgy: 3-14. London: Archetype.
CRADDOCK, P. T. 1995. Early metal mining and production. Edinburgh University Press.
HAUPTMANN, A. 2007. The archaeometallurgy of copper: evidence from Faynan, Jordan. New York:
Springer.
OTTAWAY, B., 1994, Prähistorische Archäometallurgie, Marie Leidorf, Espelkamp.
RADIOVOJEVIC, M., REHREN, TH., PERNICKA, E., SLJIVAR, D., BRAUNS, M., BORIC, D. 2010.
On the origin of extractive metallurgy: new evidence from Europe. Journal of Archaeological Science, 37,
2775-2787.
ROSTOKER, W. 1975. Some experiment in prehistoric copper smelting. Paleorient Vol. 3. No 1, p. 311 –
315.
VILLA, I. M. 2009. Lead isotopic measurements in archaeological objects. Archaeol Anthropol Sci
1:149–153.
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Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2009-2010
SUMMARY LAST YEAR’S ACTIVITY
Courses:
BOESSO, S.: “Introduzione alla biblioteca”, Dipartimento di Geoscienze, Università degli Studi di Padova.
CALANDRUCCIO, E.,: “Corso di Inglese parlato”, Dipartimento di Geoscienze, Università degli Studi di Padova.
PESARIN, F., SALMASO, L., Statistica applicata alla sperimentazione scientifica. Centro studi per l’ambiente alpino, San
Vito di Cadore.
FIORETTI, A., DI TORO, G. & ARTIOLI, G.: "Corso di comunicazione scientifica", Dipartimento di Geoscienze, Università
degli Studi di Padova.
GULICK, L.: “Corso avanzato di Inglese”, Dipartimento di Geoscienze, Università degli Studi di Padova.
NIMIS, P. “Georisorse minerarie”, Dipartimento di Geoscienze, Università degli Studi di Padova.
RASSU, A., VINANTE, C. & PRATICELLI, N.: “Introduzione a LinuX”, Dipartimento di Geoscienze, Università degli Studi
di Padova.
Schools, workshops and congresses:
BOURGARIT, D. “Archaeometallurgy at the Louvre laboratory: from Bronze Age copper smelting to Renaissance bronze
statues casting” Dipartimento di Geoscienze, Università degli Studi di Padova, 24th May 2010.
SCOTT, D.A. “Metals and Microstructures”. Dipartimento di Geoscienze, Università degli Studi di Padova . 18-21 October
2010
Field and experimental activities:
Sampling and XRPD analysis (done at the Geosciences Department, University of Padova) on mineral and slag samples to
performed statistical investigations and as preparation for lead isotopes analysis.
Isotopes separation (clean laboratory) and ICP-MC-MS analysis at Institute of Geology in Bern University: 23 – 27 March
2010 and 22 – 27 June 2010.
Petrographic characterization of slag samples by means of polarizing microscope and density measurements. Analyses
performed at the Geosciences Department, University of Padova.
Archaeometallurgical copper smelting experiment performed at Agordo (BL): from 30th June till 6th July 2010. Sampling and
cataloguing of the products.
Visit to archaeological site of Castel de Pedena (San Gregorio nelle Alpi, BL) Late Bronze Age and Montebelluna (TR)
archaeological site dated to Iron Age.
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