Per. Mineral. (2002), 71, SPECIAL ISSUE: Archaeometry and Cultural Heritage, 217-225 http://go.to/permin

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Study of an Etruscan object composed of three metals

GIOVANNA SAVIAN01*, FERDINANDO FELLI 1, MAURO CAVALLINI 1 and LUCIANA DRAG02

I Dipartimento di Ingegneria Chimica, dei Materiali, delle Materie Prime e Metallurgia Universita di Roma«La Sapienza», Italy.

2 Dip. di Scienze Storiche, Archeologiche, Antropologiche dell' Antichita Universita di Roma «La Sapienza», Italy.

ABSTRACT. - This paper reports the results ofpreliminary research carried out on one of the manymetal objects from excavations in the Sanctuary ofPyrgi (Santa Severa, Rome) near the port of Caere(Cerveteri), one of the main towns of SouthernEtruria. The metal object, found in the southern areaof the sanctuary consists of a cylinder, perhaps ahandle, originally part of an object of indefiniteshape and function. It consists of three differentlayers of metal: a central ferrous rectangular rod (10x 8 mm), surrounded by a thick lead alloy ring 21mm in diameter, and a 2-mm outer layer of copperalloy. SEM+EDS analyses were carried out on thethree components.

It seems probable that the outer copper alloysleeve was produced first. The inner iron rod was setin position and the Pb-Sn alloy was then cast to fixall three parts of the object together.

The ferrous rod was produced by deformationresulting from heating. Pb- and Cu-bearing alloyswere cast in temperature ranges of, respectively,350-300°C and llOO-800°C.

RIASSUNTO. - Si presentano i risultati delleindagini preliminari eseguite su uno dei numerosireperti metallici provenienti dagli scavi diretti dalprof. Giovanni Colonna dell'Universita di Roma «LaSapienza» nel santuario di Pyrgi (Santa Severa -Roma), sito presso il porto di Caere (Cerveteri), unadelle principali citra dell'Etruria meridionale.

Si tratta di un elemento cilindrico, forseun'impugnatura, parte di un oggetto dalla forma edalla funzione non precisabile, rinvenuto nell' areaSud del santuario, la cui documentazione,

*Corresponding author, E-mail: giovanna.savianowuniromal.it

comprendente una cospicua quantita di offertevotive databili per 10 pili tra il Veil IV sec. a.C.,testimonia la continuita del culto fino a tutto il IIIsec. a.c.

KEY WORDS: Etruria, Archaeometallurgy, Bronze,Iron, Lead

INTRODUCTION AND HISTORICAL BACKGROUND

This paper presents the results of preliminaryresearch carried out on one of the numerousmetal objects found in the excavations directedby Prof. Giovanni Colonna of the University ofRome «La Sapienza», in the southern area ofthe Etruscan Sanctuary of Pyrgi (Santa Severa,Rome), the main harbour of Caere (Cerveteri),as a contribution towards knowledge of metalproduction in South Etruria (Figs. 1, 2).

The findings in this area of the Sanctuary,which include a large number of votiveofferings mainly dating from the 5th and 4thcenturies BC, bear witness to constant worshipup to the end of the 3rd century BC (Bag1ione,1989-90; Colonna, 1992, 1996; Colonna andBaglione, 1998).

The object of this study, perhaps a handlewith its ends missing, is part of an artefact, theshape and function of which cannot yet beidentified. It is formed of a cylindrical part inlead in a bronze sleeve and an iron rod, with a

218 G. SAVIANO, F. FWELLI, M. CAVALLINI and L. DRAGO

Fig. 1 - Aerial view of Sanctuary of Pyrgi.

Fig. 2 - Aerial view of southern part of Sanctuary of Pyrgi.

Study ojan Etruscan object composed ofthree metals 219

«ghiande missili»), dating from the 5th and 3rdcenturies Be. Bronze goods include tools andvases. Among the findings in copper, mostnoteworthy is a significant group of pieces ofaes rude, mainly found in the square of thesouthern area.

The aim of analyses, so far carried out onsamples of the main categories of metalfindings from both northern and southern areas(iron weapons, aes rude, ingots, clamps, leadmissiles) and on a sample from theexamined here, is to gain information onmetallurgy techniques and to determine theprovenance of the raw materials, within thebroader framework of a study on metallurgy,sources of supply, and circulation ofmaterials in South Etruria (Tanelli, 1983,Zifferero, 1991, 1996; Caranc ini , 1996;Giardino, I 1998; Boni et al., 2000;Brocato, 2000;). Lead isotopes e06Pb/204Pb,207Pb/2o4Pb, 208Pb/2o4Pb) have been analysed inmany lead objects from various parts of theItalian peninsula. Etruscan lead ingots from thePyrgi temple (Caere , 5th century BC) showisotopic fingerprints of the mining district ofsouthern Tuscany (Boni et al., 2000).

METHODS AND TECHNIQUES

3 shows the metal object. A transversalthin metallographic section was cut from it adiamond saw and embedded in epoxy-type

MA2» cold mounting resin.Because of the great brittleness of the outersleeve of the object, many chips were producedand lost during cutting.

. 4 shows an overall view of thespecimen, which was examined opticalmicroscopy. It was then sputtered with a thinfilm of carbon produced by evaporation, forScanning Electron Microscopy +Energy Di spersion Spectroscopy (EDS)analyses.

Quantitative analyses were carried out forinformation on the various components,impurities, and interphases between metals,where corrosion effects are more interesting.

square cross-section, probably running fromone end to the other. The rod is visibleprotruding from the end of the artefact. Thedetail of a lead core coated by a bronze sleeveis typical, for example, of the handles of roundshields of rolled bronze, in use from a veryadvanced phase of the First Iron Agehalf of 8th century

The technical characteristics of the object areextremely interesting, because it is an exampleof metallurgy, different metalsand in juxtaposiuon.

Its main interest lies not only in the use in thesame object of three different metals but also ofthe - iron, lead and bronze -,'o,...rO('Olntp·r! in the of Pyrgi in several

of materials. studied(Drago et al., ] 2000 a, 2000 b; Cavalliniet

Among the iron objects there is also a largegroup of arrow-heads - more than five hundred- found in the fill of the square of the southernarea of the together with largenumbers of Attic ceramics and other metal andceramic findings. These objects form a sort oflarge secondary votive sealed at thelatest at the mid-4th century and have beenrelated to the to theFaliscan god Apollo SOJ'({l1US, the Greekthe Latin Dis Pater and the Roman vediovis.

the findings, ten lead ingots are offJ~lJl LH., "" 'cu interest. are prismatic inhave a more or less regular trapezoidalsection, and betweenand 21 were found in thesouthern area of the , under thefoundations of altars and buildings dedicated toSuri in the 5th century Be. They are similar incomposition but not in shape to the small leadingots from the archaic wreck found atCampese Bay (Isola del Giglio) (Bound, 1991;Craddock and La 1991; Cristofani,1998).

Other lead objects found in the northern andsouthern areas of the Sanctuary are manyclamps and lead pieces, partly used to fastenterracotta decorations to the wooden parts ofthe temples, and numerous «rnissili» (so called

220 G. SAVIANO, F. FWELLI, M. CAVALLINI and L. DRAGO

Fig. 3 - Two aspects of studied object.

Study ofan Etruscan object composed ofthree metals 221

Fig. 4 - Transversal section of object embedded in resin.

RESULTS

EDS analyses of the outer ring show that it ismade of bronze, with the followingcomposition: 84.1% Cu, 13.9% Sn, 1.8% Pb,0.2% Fe. Corrosion morphology is clearlyshown in fig. 5, in which a penetration of about1 mm is evident. Metallographic examinationreveals a heterogeneous pattern of dendrites(acu solid solution) and a+8 eutectoid areas.The darker constituent in fig. 6 is acu' withmaximum Sn contents of 4%; the lighterconstituent is an a+8 eutectoid with Sncontents over 20%. Pb is associated mainlywith the 8 phase. The X-ray map of Cu and Snis also shown in fig. 6. The dendritic structureclearly indicates that the sleeve was producedby a casting technique.

A thin layer of metallized iron was detectedat the interface with the inner ring (fig. 5),which consists of a Pb-Sb alloy with 1.1% Sband about 0.5% Cu.

The central ferrous rod appears to be fullymineralized, as usually occurs, and consists ofvarious oxidation products (iron oxides,oxyhydroxides). The whole rod presents manycracks particularly at the Fe-Pb interface, asshown in fig. 7. Silicon and aluminium-richinclusions are shown in fig. 8.

DISCUSSION AND CONCLUSIONS

Metallographic and analytical results suggesthow the object was made. Some indicationsabout ancient mines will also be discussed.

222 G. SAVIANO, F. FWELLl, M. CAVALLlNI and L. DRAGO

Fig. 5 - SEM micrograph of outer bronze ring. Externalsurface shows corrosion products; internal interfacetowards Pb-Sb alloy is still metallic, with mineralized ironlayer.

Fig. 6 - Micrograph of dendritic structure of bronze, and X-ray map of Cu and Sn.

Study ofan Etruscan object composed of three metals 223

The outer bronze ring was produced first.The presence of dendritic structures suggestscasting of a (lost wax?) plane sheet with arougher inner surface, worked while hot on abarrel to give a cylindrical shape. The loss ofcontinuity in the cylindrical ring but thepresence of an overlap along a generatrix,support this idea. The thin layer of mineralizediron, found at the bronze-lead interface, isprobably due to deposits of iron-rich corrosionproducts from the inner rod or to corrosion oflocal residues from the working process.

The inner iron rod was set in position and thePb-Sb alloy was then cast, to fix the parts of thewhole object together.

As regards the metals:- the outer bronze sleeve is a typical Cu-Sn

alloy with low Pb contents. It appears to behomogeneous and has few inclusions. Thealloy is quite different from the previouslystudied aes rude found in the same site (Drago

Fig. 7 - Micrograph of interface between mineralized Feand Pb-Sb alloy.

et al., 2000 b), which consisted of metalliccopper with mixed iron and copper sulphides,and other lead and bismuth impurities;

- the Pb-Sb alloy is very similar incomposition to previously studied ingots(Drago et al., 2000 a), suggesting that its orecame from typical regional mineralized areaslike the mountains of Tolfa or southernTuscany, where galena with such acomposition was mined (Rolandi, 1956;Tanelli, 1983, 1989; Zifferero, 1991, 1996;Carancini, 1996; Giardino, 1996, 1998; Saez etal., 1996; Brocato, 2000).

- the morphology of the mineralized iron isdifferent from that of the iron arrow-headsfrom the same site (Cavallini et al., 2000), asits inclusion contents consist of Si- and Al-richproducts, typical of local ores, instead of thepuzzling Ca-rich inclusions of the arrow-heads(Panseri, 1957; FolIo et al., 1988; Gauzzi et al.,1996; Mapelli and Nicodemi, 2000).

Fig. 8 - Silicon- and aluminium-rich inclusions insidemineralized iron rod.

224 G. SAVIANO, F. FWELLI, M. CAVALLINI and L. DRAGO

It should not be forgotten that the three alloysstudied here differ greatly from the technologicalpoint of view: the iron rod was produced by hot

.deformation, whereas the Pb- and Cu-bearingalloys were cast in temperature ranges of,respectively, 350-300°C and llOO-800°C. Thetemperature of iron reduction was not higherthan that of the copper alloy, because directreduction was involved, with no need to reachmelting temperature (l536°C for pure iron).

This study of an Etruscan object composedof three metals confirms the high metallurgicalskills (Tylecote, 1988) of the old craftsmen,who were capable of handling different kindsof alloys. Knowledge of very differenttechniques and ores coming from several minesconfirm the metallurgical and commercialability of the Etruscans.

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