Studio archeometrico di ceramiche rinvenute a Pompei (scavi I.E. 1980-81): provenienza e tecnologia di produzione
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Scarpelli, Roberta
Pantano, Pietro
De Francesco, Anna Maria
Cottica, Daniela
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Scuola di Dottorato "Archimede" in Scienze Comunicazione e Tecnologie, Ciclo XXVI,a.a. 2013; The following work focuses on the archaeometric characterization of different pottery classes
found in Pompeii during the I.E. excavations in 1980-1981. These investigations, carried out in the
western part of the Forum, during the installation of the electric cables (I.E.= impianto elettrico),
revealed numerous useful materials for the reconstruction of the first stages of the city.
The ceramic, is certainly the most attested material and its study, allows to obtain archaeological
information on many aspects of the past, as chronology, trade and technology.
The analyzed ceramics, were selected by three major groups: common ware, black-glaze pottery
and votive material. The choice of the samples was not random, because these ceramics classes
were widespread in everyday life and in the ancient Mediterranean trades.
Archaeometric study aimed to investigate ceramic samples to obtain information related to tthe
Pompeii production, its social organization and the possible exchanges of finished objects. The
results allow us to reconstruct ancient trades, in which Pompeii was great protagonist.
The common ware, including cooking ware (jars and pots) and plain ware (jars and bottles), is
certainly the most attested production. The great variability of shapes and fabric, in particular for
cooking ware, suggested a wide diffusion, in Pompeii, of products, not only of local production.
The first part of the study involved the petrographic, mineralogical and geochemical
characterization of local cooking ware and dated in a wide time span (IV-I century BC).
The petrographic comparison between two groups, dating to IV-III century BC and II-I century BC,
evidenced, the presence of same mineral phases and fragments of volcanic rocks, related to
Somma-Vesuvius activity. The differences, between two groups, were related to higher content of
the coarse fraction for younger products (II-I century BC), suggesting changes in the production
technology. We could hypothesize the use of non-calcareous clay with the addition of temper for
the production of the oldest ceramic and the employment of weathered volcanic deposits for the
later typology. Technological differences related to firing temperatures, are also showed. The presence of micas
and hematite, detected by XRD analysis, indicates firing temperatures ranging between 800-900°C
for both groups (Riccardi et al., 1999 and Cultrone et al., 2001). A greater variability was found in
the II-I century BC group in which the absence of micas, in some samples, allowed to indicate
slightly higher temperatures.
The second part of the research focused on the comparison of II-I century BC pottery with two
coeval groups of pottery (called group c and group d), characterized by the same ceramic form but
with a different fabric.
The petrographic analysis distinguished a volcanic fabric for a group c and a granitic fabric for the
group d. For the latter one, considering the different geological characteristics of the Campanian
area, it’s possible to indicate as possible provenance area, Calabria and Sardinia. However further
analysis are necessary to confirm these hypotheses.
From the mineralogical point of view, group c showed a temper similar to the local group (group
b). Plagioclase, sanidine, clinopyroxenes, amphibole, biotite and a large amount of volcanic rock fragments, were observed in both groups. The differences are related to the increased presence and
variability of clinopyroxenes in the group b and on the contrary of higher content of sialic minerals
(plagioclase, sanidine and quartz) in group c. In group b, the quartz was detected only by XRD
analysis.
On the basis of petrographic characteristics, it is not possible to exclude the local origin for the
group c, while the different chemical composition detected by XRF analysis does not allow to
advance other hypotheses.
In general, the mineralogical association, plagioclase, sanidine and pyroxene, is very common in
volcanic areas, both in the Campanian magmatic Province (Somma-Vesuvius, Campi Flegrei and Roccamonfina) and in the Roman co-magmatic Province (Vulsini, Vico and Sabatini) characterized
by similar volcanism (KS and HKS). The Alban hills are excluded because the products do not
contain plagioclase and sanidine (Gaeta et al., 2006). Anyway, the traditional comparison with
local raw materials, to have indications of provenance, is particularly difficult and not very useful,
considered the coarser fabric of the ceramics. Therefore micro-analysis on individual volcanic phases (clinopyroxenes), were performed on the pottery wares. This method was considered as a
good discriminant tool in recent works (Comodi et al., 2006; De Rosa et al., 2007, Barone et al.,
2010).
The clinopyroxenes of the ceramics in groups b and c were compared with clinopyroxenes of
igneous rocks of the Campanian volcanic districts (Somma-Vesuvius and Roccamonfina) and
Roman districts (Vulsini, Vico and Sabatini). The pyroxenes analyzed in both ceramics and rocks,
were classified on the basis of Morimoto et al.,1988, as diopside. Some trace elements: V, Sr, Zr, Y
and REE (rare earth), detected by LA-ICP-MS, were selected to discriminate each group of
ceramics, the pyroxenes of the Roman co-magmatic Province and of Campanian magmatic Province. The comparison between the pyroxenes of ceramics with those contained in the rocks, by
statistical processing (binary diagrams and multivariate analysis, PCA) confirms the compositional
similarity between the pottery of group b (considered local production) with pyroxenes of Somma-
Vesuvius and Roccamonfina, and the similarity of the group c with pyroxenes of Roman districts.
Therefore this method, was perfectly valid in this study, because allowed us to confirm the locally
provenance for the group b and to exclude it for the group c. Moreover, a possible area of origin for
the group c was also suggested. The black glaze pottery is dated in a wide time span (IV -I century BC) and it was considered on
the basis of archaeological evidence (presence of misfired potteries and furnace spacers) of local
production. The possible furnace of production is not been found yet and the archeological
attribution of the provenance, on the basis of the very fine fabric, did not give sure information. For
this reason, archaeometric analyzes were performed in order to investigate local productions and to
clarify the technological changes for over three centuries. Two different groups of ceramics dated
to the IV-III century BC and II-I century BC were selected for the analysis. No compositional
differences were detected by petrographic and chemical (XRF) analysis. Conversely, the study on
black glazes by SEM/EDS and by Raman microscopy (performed at the Department of Chemistry,
University College London, UCL), evidenced mineralogical and morphological variations clearly
due to a different control of the firing conditions. The early ceramic samples (4th–3rd century) are characterized by a sintered coating in which small crystals of iron oxide content are widespread.
Magnetite, hematite and hercynite represent the mineralogical phases recognized by Raman
microscopy. The later production is characterized by a completely vitrified glaze containing only
magnetite. The differences are due, probably, to the different firing practice, in particular as regards
the reducing step, that is, the values of the temperature and period of duration of this phase and the
cooling rate (Scarpelli et al., 2014).
Finally, in order to confirm the local origin, the possible raw materials used for the production of
this ceramic class, were sampled and compared chemically by binary diagrams. On the basis of
archaeological indications (Peña and McCallum, 2009) and the geological characteristics of the
studied area, clayey materials were individuated in the Salerno province, at Ogliara and at
Montecorvino Rovella. These calcareous clayey sediments (15% of CaO), belonging to the Mio-
Pliocene sedimentary sequence of the basin of Salerno, show a large compositional similarity with
the analyzed ceramics, confirming the hypothesis of Peña and McCallum. Petrographic comparison with the experimental tests of clay fired at 900 °C, confirms these similarities and a greater
depuration for the oldest group of ceramics.
These results allowed to attest, for the first time, a Pompeii production of black glaze ceramic that,
could be considered as reference group; secondly these suggested some considerations relating to
the management of ancient quarries in the area of Salerno, which were probably used by potters in
a quite extensive area. The study on the votive material is in a preliminary phase yet. Thymitheria, figurines and miniature
vessels, characterized by different forms and fabric, were analyzed. On the basis of archaeological
assumptions these materials could be considered as local production of workshops (not yet
identified) for devotees. Petrographic analyzes have confirmed the compositional differences
between the three groups but also inside the same group, and allowed us to indicate the
employment of more raw materials (fine clays, clays and volcanic temper, weathered volcanic
deposits) for these products. These results could ascertain the presence of more ceramic ateliers specialized in the production of different potteries or, simply, verify the supplying of clayey
materials from different sources in the Vesuvian area.; Università della CalabriaSoggetto
Geologia; Archeometria; Ceramiche
Relazione
GEO/09;