microstructural characterization of early western greek incuse coins. archaeometry 47, 2005

Archaeometry

47

, 4 (2005) 817– 833. Printed in Singapore

*Received 6 April 2004; accepted 20 September 2005.© University of Oxford, 2005

Blackwell Publishing, Ltd.Oxford, UKARCHArchaeometry0003-813X© Unviersity of Oxford, 2005November 2005474

ORIGINAL ARTICLE

Early western Greek incuse coinsG. Giovannelli et al.

MICROSTRUCTURAL CHARACTERIZATION OF EARLY WESTERN GREEK INCUSE COINS

*

G. GIOVANNELLI and S. NATALI

Dipartimento ICMMPM, Università di Roma ‘La Sapienza’, via Eudossiana 18, I-00184 Roma, Italy

B. BOZZINI

Dipartimento di Ingegneria dell’Innovazione, Università di Lecce, via Monteroni, I-73100 Lecce, Italy

and A. SICILIANO, G. SARCINELLI and R. VITALE

Dipartimento dei Beni Culturali, Università di Lecce, via D. Birago 64, I-73100 Lecce, Italy

In this research, we studied the compositional, crystallographic and microstructuralproperties of a series of incuse silver didrachmae stemming from the Achaean colonies ofMetapontum and Caulonia. In this paper, we address the following points: (i) the metalsources, (ii) the fabrication process and (iii) degradation phenomena, such as incrustationand embrittlement. In this investigation, we employed energy-dispersive X-ray fluorescencespectroscopy, X-ray diffractometry, and scanning electron and optical microscopies. Thepatina is mainly composed of chlorargirite. The coins consist of a silver-rich alloy contain-ing

∼

1% of Au and Cu. Metallographic and local compositional analyses revealed a complexscenario of inclusions. In one instance, unalloyed copper grains, two-phase copper/bismuthglobuli and high-bismuth filaments were observed. In other cases, globular Cu

2

S (chalcocite)inclusions were noticed. The presence of SiO

2

and iron oxide inclusions is ubiquitous in thesesamples. Distorted twin lines and strain lines can be detected, denoting work-hardening ofrecrystallized flans. Grain polygonalization can occasionally be noticed, hinting at sec-ondary recrystallization processes. The irregularly shaped iron oxide particles often act as crackinitiation sites. Fracture facets are generally intergranular. On some areas, intergranulardecohesion is also observed. Open cracks sometimes contain AgCl. The strain lines that canbe noticed on the fracture surfaces indicate work-hardening and residual microstructuraldeformation. Information regarding inclusions and the presence of significant amounts ofgold can be tentatively used to address provenancing and fabrication issues.

KEYWORDS:

INCUSE COINAGE, SILVER, CHLORARGIRITE, CORROSION, EMBRITTLEMENT, SOUTHERN ITALY, SEM–EDX, XRD

*Received 6 April 2004; accepted 20 September 2005.

INTRODUCTION

The incuse coinage technique began in the Greek colonies of southern Italy in the second halfof the sixth century

bc

. Incuse minting activity is reported for Sybaris, Metapontum, Crotonand Caulonia, a group of neighbouring sites mainly in Lucania (Gorini 1975). In this manu-facturing technique, which is the earliest example of the silver coinage of the Greek colonies

818

G. Giovannelli

et al.

in southern Italy, an intaglio obverse die was hinged at or aligned against a positive reverse diein order to obtain an incuse (i.e., impressed into the surface) reverse of the obverse type. By450–440

bc

, the incuse reverse had disappeared and its place was taken by the more familiarreverse type in relief.

The reason for the choice of the incuse fabric is not entirely clear: a host of explanationshave been put forward, ranging from ease of stacking to Pythagorean cosmology (Rutter 1997).Incuse coinage is believed to be an unparalleled indigenous technique, and yet the thin flan mayhave been influenced by the earliest coins at Corinth. Such coins have never been retrieved inlocations that are significantly remote from the original minting sites (Rutter

et al

. 2001).This research deals with the elemental composition and the microstructural characteristics

of a set of incuse coins.Two main silver sources were available to the Greek and Roman world in classical times:

(i) polymetallic ores from the secondary Jarosite deposits in Huelva, and (ii) the argentiferousgalena mines of Laurion on the Greek mainland and on some Aegean islands. Nowadays, it isgenerally accepted that other silver deposits (in Anatolia, Sardinia, Saudi Arabia, Iran andAfghanistan) must have been exploited by the ancient metallurgists (Rehren

et al

. 1996).Rigorous provenance studies (Stos-Gale 1998) have been carried out on the archaic Greek silvercoins stemming from the mainland and the Aegean islands. Only analytical chemical invest-igation techniques (mainly thermal ionization mass spectrometry, TIMS) have been utilized,to the best of the authors’ knowledge. Consequently, no microstructural characterization ofsimilar artefacts is available. Lead isotope analysis has proved that the chief sources for thesecoinages corresponded to argentiferous galena from the Laurion and Siphnos mines. The silversources of a small number of Aeginetan coins and of some

Wappenmunzen

from the investig-ated hoards, both of which exhibit a singularly high gold content, have not yet been identifiedsatisfactorily. Neither elemental analyses nor lead isotope ratio studies are available for west-ern Greek incuse coinage, and therefore no conclusive scientific provenance studies have yetbeen accomplished.

On the basis of the paucity of local sources of silver and the assumption that whether or nota city minted coins depended upon the supply of bullion, the opinion has been expressed in thepast (Milne 1931, 1938; Sutherland 1942, 1948) that these coins should derive from overstrikingof earlier foreign issues. This view, which lacks conclusive textual and material evidenceas far as western Greek civilization is concerned, has been rejected in Noe (1957). Silver wasindeed mined in the sybaritan areas of Longobucco (Lenormant 1881) and S. Marco (ZancaniMontuoro 1965–7; Gorini 1975; Will 1975; Kraay 1976; Garraffo 1984) in the Middle Ages.

It is worth noting that, in an attempt to discover the geological sources of metal artefacts,unalloyed and single-sourced metals are required (Ixer 1999). Greek coins from the mainlandand Aegean area of the sixth and fifth centuries

bc

are generally believed to consist of silverobtained from a single mine site. This working hypothesis was adopted by Gale

et al

. (1980)on the basis of the conjecture that in archaic times the Greeks—who were among the earliestable to mint silver—mainly relied on their own sources for bullion supply. This hypothesis hasbeen confirmed experimentally

a posteriori

by the observation of a high uniformity of the leadisotope composition.

In the past decade, large hoards (Dor, Tel Mique-Ekron and Shechen) of pieces of pre-weighed and sealed silver (known as

Hacksilber

), dating back to the Iron Age period, havebeen excavated in the Eastern Mediterranean. The lead isotope analyses (Stos-Gale 2001) forthese hoarded silvers indicate that the metal derived from at least three different regions:Spain, Iran and the Aegean area. These findings confirm a monetary or pre-monetary usage of

Early western Greek incuse coins

819

silver all over the Mediterranean basin. In this regard, the role of the Mediterranean silvertrade and of the Near Eastern silver hoards in the birth of coinage has recently been deepenedin the comprehensive research of Thompson (2003). It has also been observed that in all caseswhere simultaneous use of silver from different sources is suspected, the possibility that suchmetal was mixed cannot be excluded (Price 1980). The lead isotope data collected so far,while often indicating several distinctly different mine sites for objects deriving from the samehoard, do not yet support the hypothesis of metal mixing from different sources within a singleobject. As a matter of fact, the distinctive lead isotope fingerprints are basically preserved inthe single investigated items.

A complete summary of the literature on ancient silver metallurgy is not possible here.Craddock (1995) provides an excellent staging point, with a clear discussion of key issues andan up-to-date bibliography. Only some details relevant to the present discussion will be givenhere. Recent studies on silver extraction (Rehren 2003) maintain that the chief silver sourceemployed in antiquity was argentiferous lead ores. A marginal role is consequently assignedto both native silver and pure silver minerals. Agricola, writing in the 16th century, onlydevotes a few lines of his bulky treatise to the smelting of nearly pure silver ores, and treatsthe subsequent metallurgical processing steps of the metal from the primary smelt of these oresaccording to the conventional lead/silver extraction and refining processes (see Agricola 1950).Evidence of extractive metallurgy dating back to the seventh and sixth centuries

bc

has beenrecovered at both Spanish and Greek sites (Conophagos 1980; Kassianidou

et al

. 1995). Excavationsat Monte Romero have produced convincing evidence of preliminary ore roasting of polymetallicores from Spanish mines. This research has also confirmed that the final silver-bearing layerfound in the smelting furnace was always argentiferous lead. This finding was proved both forthe case of smelting carried out by deliberate addition of lead (a processing additive employedin order to enhance the collection of silver metal—this was the most widespread process duringRoman times) and for the case of the native presence of lead in the raw material.

It is universally accepted (Craddock 1995) that ore smelting in the Greek operations wasa batch process composed of two sequential steps: (i) partial sulphide roasting and (ii) self-reduction of the partially roasted galena. The overall reaction is PbS + O

2

→

Pb + SO

2

. Ther-mochemical calculations based on the Ellingham diagrams for metals, metal oxides and metalsulphides (Lupis 1983) indicate that the standard free energies of oxidation of metal sulphidesper mole of O

2

at 1000

°

C are

∆

G

°

(FeS/Fe

2

O

3

) =

−

247 kJ,

∆

G

°

(PbS/PbO) =

−

208 kJ and

∆

G

°

(Cu

2

S/Cu

2

O) =

−

170 kJ. This shows that copper sulphide can survive conditions leadingto partial roasting of PbS. The metal resulting from the primary smelt was refined by extensiveoxidation of lead. This extremely ancient process, known as cupellation, is still routinelyemployed as an accurate test method for precious metals.

Free energy versus temperature diagrams allow us to predict the oxidation behaviour of the metalsdissolved in the argentiferous lead underlying the liquid litharge. Standard molar free energychanges at 1000

°

C for the reactions 2Pb + O

2

→

2PbO, 4Cu + O

2

→

2Cu

2

O and 4Bi + 3O

2

→

2Bi

2

O

3

are

∆

G

°

(Pb/PbO) =

−

191 kJ,

∆

G

°

(Cu/C

2

O) =

−

154 kJ and

∆

G

°

(Bi/Bi

2

O

3

) =

−

152 kJ, respectively.This indicates that elemental copper and bismuth cannot be oxidized directly by the litharge.Therefore, their conversion to oxides relies mainly on the oxygen partial pressure and on thepartition ratio between the two liquid phases. A comparison of the numerical values of

∆

G

°

(Pb/PbO) and

∆

G

°

(Cu

2

S/Cu

2

O) reveals that a similar behaviour is expected for copper sulphide.As far as the final concentrations of these metals in refined silver is concerned, it is generally

believed that if the cupellation is allowed to run to completion (i.e., lead attains a final concentra-tion below 1%), bismuth can survive the process to a certain extent and can be eliminated only

820

G. Giovannelli

et al.

by subsequent oxidation steps (McKerrell and Stevenson 1972). Since the latter metal survivesthe cupellation process, a high bismuth content may be indicative of a bismuth-rich (e.g.,polymetallic) ore.

No conclusive evidence is available regarding silver processing methods meant to recovergold before the medieval period (Craddock 1995). We therefore believe that the gold contentof the investigated items can provide useful indications for the tracing of ore sources. It isgenerally believed that silver from lead sulphide ores contains no more than 0.1% of gold,but it has been reported that the Au/Cu ratio may be higher than 0.25% in the weathered orezones (Meyers 1986). Consequently, the high gold levels found in the earlier silver artefactsare generally taken as an indication that oxidized lead ores, rather than galena, were primarilyexploited for silver.

THE INVESTIGATED ARTEFACTS

Five coin fragments (identified as M1, M2, M3, M4 and M5) resulting from occasional dis-coveries in the Salentine region (southeastern Italy) have been investigated. The fragmentspertain to silver staters issued by the Achaean colonies of

Metapontum

and

Caulonia

.Metapontum was founded in the mid-seventh century. The standard coin type of the city is an

ear of barley. The relevant minting activity began in

c

. 540

bc

with the adoption of the incusetechnique. The beginning of the double relief coinage dates from

c

. 440

bc

(Rutter

et al

. 2001).Caulonia was founded early in the seventh century; its coinage did not begin until the last

quarter of the sixth century, with the adoption of the incuse technique, up to the change todouble relief after

c

. 475

bc

(Rutter

et al

. 2001).These fragments have been subjected to the investigation described below in as-found con-

ditions. As illustrated in Figures 1–5, these items exhibit the following characteristics. (i) Theyare heavily encrusted, with insoluble substances overlying the original metal volume, such thatthe original surface remains as a pseudomorph composed of corrosion products. (ii) Themetallic remnants are severely embrittled. As a consequence, friable and powdery fragmentsderiving from both the patina and metallic remnants are typically found at the bottom of the

Figure 1 Coin fragment M1—LUCANIA, Metapontum; c. 540–510 BC. AR, Spread incuse stater: barley-ear/barley-ear incuse (Rutter et al. 2001).

Early western Greek incuse coins

821

cases containing these items. Single fragments have been subjected to different investigationsafter mechanical separation.

EXPERIMENTAL

Structural characterization was performed by XRD, using a Philips PW 1830 diffractometerequipped with a Philips PW 1820 vertical Bragg–Brentano powder goniometer and a Philips1710 control unit. The scan rate adopted was 1 deg s

−

1

. The radiation employed was unmono-chromated Cu K

α

. The measurements were carried out either directly on the samples or onpowders collected from the relevant containers and pressed into standard powder-sample holders.


Figure 3 Coin fragment M3—BRUTTIUM, Caulonia; c. 525–500 BC. AR, Spread incuse stater: Apollo standing on the right, a branch in his raised right hand; on his extended left arm, a small figure carrying branches; in the field,a stag with its head turned back; KAYΛ/same type incuse; no legend (Rutter et al. 2001).

822

G. Giovannelli

et al.

The morphology of the samples was studied with a Cambridge Stereoscan 360 SEM. Theelectron source was LaB

6

. Electron detection was carried out using a scintillation photodetector.The typical working pressure was 10

−

7

mbar. Optical microscopy observations were performedon a Leitz Laborlux 12 ME S attached to a Nikon Coolpix 3500.

Quantitative analysis of the sample composition was performed by EDX in the same vacuumchamber and with the same electron source as SEM, with a Li-doped Si detector. Compositionaldata have also been collected by means a dedicated ED-XRF spectrometer (Spectro X-test, lateralresolution of 1

×

1 mm

2, penetration range about 20 µm), equipped with a Cu anode and alight element detector, only suitable for qualitative analysis.

Figure 4 Coin fragment M4—BRUTTIUM, Caulonia; c. 525–500 BC. AR, Spread incuse stater: Apollo standing on the right, a branch in his raised right hand; on his extended left arm, a small figure carrying branches; in the field, a stag with its head turned back; KAYΛ/same type incuse; no legend (Rutter et al. 2001).


Early western Greek incuse coins 823

THE PATINA AND THE LOOSE METALLIC REMNANTS

SEM–EDX and XRD analyses of the patina

Powdery fragments of the encrusting patina collected from the boxes containing M5 and M3,respectively, have been subjected to SEM–EDX and XRD investigations. These analyses haveshown that the patina is primarily composed of chlorargirite. Figure 6 shows an X-ray diffracto-gram of the powder that had spontaneously fallen off coin M5, and that was collected fromthe container: a two-phase fcc silver–chlorargyrite structure can be noticed.

Some particles containing Ca, Fe and Al were also detected by SEM–EDX. These resultsindicate that the patina is mainly formed of mineral alteration products, with a contributionfrom soil contaminants. The relevant deposition soils exhibit a moderately calcareous nature(Rusco et al. 2001) and are characterized by the secondary accumulation of iron- and aluminium-containing minerals. Such taxonomic properties denote peculiar palaeoclimates, implyinga higher average temperature and humidity than at present. As pointed out in McNeil and Little(1992), a typical example of silver corrosion is conversion of silver to cerargyrite. Cerargyritehas been shown to be stable in seawater and chloride-rich shallow land burials. Effectiveoxidizing conditions are found near shallow land burials, where the major source of ground-water is rain or surface water percolating through soils. Deep groundwaters and waters fromcoal-mines may not fit this particular model (Garrels and Christ 1965). The presence ofthe kind of patina that we found in our research is therefore a clear indication of the type ofdeposition environment.

SEM examination of the loose metallic remnants

SEM fractography of a loose fragment of sample M5 allowed us to identify the micro-featuresrelated to the embrittlement process.

Figure 6 An X-ray diffractogram of the powder released by the encrusting patina.

824 G. Giovannelli et al.

As shown in Figure 7, the fracture facets are almost completely intergranular. On some areas,intergranular decohesion is also observed. The strain lines that can be noticed on the fracturesurfaces indicate work-hardening and residual microstructural deformation. As revealed byFigure 8, open cracks are partially filled with an extraneous material, that local EDX analysesshowed to correspond to AgCl.

Figure 7 SEM fractography of coin fragment M5.

Figure 8 The filling of open cracks by corrosion products.


ED-XRF analysis of the metal surface

Table 1 presents ED-XRF elemental analyses performed on the five coin fragments. Owing toits comparatively good lateral resolution (see the ‘Experimental’ section), this analysis is wellsuited for compositional mapping of the relevant objects. In order to gain insight into surfacede-alloying and local compositional variations, we applied a micropolishing procedure inseveral (typically five) locations of each fragment. We carried out, sequentially, a certain amountof polishing and the measurement of a local XRF spectrum, the procedure being repeated untila constant composition was achieved. These results indicate that the bundles employed for thefabrication of these coins had a total silver and gold content similar to that of the majority of thearchaic Greek coinage. Any metal other than those listed in Table 1 was below the detectionlimit (∼ 0.2%).

METALLOGRAPHIC EXAMINATION OF THE METAL FRAGMENTS

Loose metal fragments (of volume 0.10–0.20 mm3) from samples M1, M2, M3 and M5 havebeen vacuum impregnated with a low-viscosity epoxy resin, then subjected to standard polish-ing treatments. A mounted sample deriving from coin fragment M5 was etched with an acidi-fied thiourea solution. EDX observations in cross-section revealed, in all of the investigatedsamples, the embedding in the metal matrix of several microlites of composition SiO2 accom-panied by irregularly shaped iron oxide inclusions (Fig. 9). The EDX spectrum (Fig. 10)exhibiting a clear O peak and the morphology of these inclusions confirm that the silicaceousparticles are not residues from grinding.

EDX analysis performed on cross-sectional areas free from inclusions confirmed the ED-XRF compositional results. No supersaturated Ag-rich solid solution was detected, sincecopper was almost entirely distributed in its unalloyed state. A detailed description of theobserved metallographic features is given below.

Metal fragment M1

Cross-sectional observations performed with backscattered electrons revealed local clusters ofmetallic inclusions of globular shape aligned along the grain boundaries. The composition ofthese inclusions varied from almost pure copper grains (Fig. 11) to two-phase copper/bismuthglobular features (Fig. 12). Filamentary bismuth-rich inclusions ∼ 20 µm long were alsodetected (Fig. 13). An EDX spectrum corresponding to a filament-like Bi inclusion is shownin Figure 14. It is worth noting that in this spectrum no signal can be detected in the oxygen

Table 1 Results of ED-XRF analyses of the investigated coins

Sample ID Description % Ag % Au % Cu % Pb

M1 Metapontum coin fragment 98.1 1.1 0.6 <0.2M2 Metapontum coin fragment 98.5 <0.2 0.6 0.7M3 Caulonia coin fragment 98.5 0.4 0.6 0.5M4 Caulonia coin fragment 98.2 0.4 0.8 0.6M5 Metapontum coin fragment 98.8 <0.2 0.8 <0.2


Figure 9 Fragment M3: a backscattered electron image indicating silica and iron oxide inclusions.

Figure 10 Fragment M3: an EDX spectrum from a silica inclusion.


channel, while a peak well above the background noise was detected in the case of SiO2 inclusions(Fig. 10). The volume fraction for these inclusions, estimated according to a stereologicalmethod devised by some of the authors (Bozzini and Giovannelli 1996), evaluates to 2.2 ±0.3%. No copper sulphide inclusions were revealed.

Figure 11 Fragment M1: a backscattered electron image indicating almost pure copper inclusions.

Figure 12 Fragment M1: a backscattered electron image indicating two-phase copper/bismuth inclusions.


Metal fragments M2, M3 and M5

These items exhibit a very similar microstructure. A substantial number of irregularly shapediron oxide inclusions are detected, acting as crack initiation sites (Fig. 15). Globular Cu2S(chalcocite) inclusions can also be noticed (Fig. 16). The etched specimen from M5 (Figs 17

Figure 13 Fragment M1: a backscattered electron image showing bismuth-rich filamentary inclusions.

Figure 14 Fragment M1: an EDX spectrum from a filamentary bismuth-rich inclusion.


and 18) shows deformation twins and strain lines within the grains. These features, whichdenote work-hardening on recrystallized flans (Scott 1991), reveal that the striking processmust have been performed at ambient temperature. Large polygonal grains possessing concaveboundaries are observed (Fig. 18), suggesting that secondary recrystallization has taken place.

Figure 15 Fragment M2: iron oxide inclusions acting as crack initiation sites.

Figure 16 Fragment M3: a backscattered electron image showing chalcocite inclusions.


Figure 17 Fragment M5: an optical microscopic image of the etched sample.

Figure 18 Fragment M5: a secondary electrons image of the etched sample.


This implies that the metal employed for the fabrication of these coins underwent annealing ata temperature well above that at which primary recrystallization occurs.

Corrosion and embrittlement

The topic of corrosion and embrittlement of archaeological silver artefacts has been exten-sively covered in Wanhill (2003, and references cited therein). This well-documented kind ofdamage can be triggered by environmental or microstructural factors; synergistic actions havebeen highlighted. The microstructural mechanism is due to the segregation of metallic impuri-ties, while the corrosion-induced embrittlement is chiefly due to galvanic coupling effects.This latter process can be enhanced by internal residual stresses. An explanation for the dam-age to our samples can be approached within the framework put forward in this reference. Inparticular, stress corrosion cracking associated with a process of active path corrosion focusedalong grain boundaries should be considered as a source of intergranular failure, owing to thesevere work-hardening that these items exhibit. We can stress one additional factor: the presenceof non-metallic inclusions. This point has not been explicitly addressed in Wanhill (2003), butcan in principle be accounted for both in the chemical and the mechanical models proposedin this paper. It is worth noting that, owing to the composition of our samples, secondaryprecipitation is not expected.

CONCLUSIONS

The silver artefacts analysed in this research have been produced from metal obtained by arefining process that cannot be described as the historical cupellation procedure reported inmodern texts and confirmed by excavations of Roman metallurgical installations. Theobserved iron oxide inclusions can hardly be reconciled with the metal oxide scavengingaction of molten litharge. Most probably, the metal from the primary smelt must have justbeen re-melted under a strong blast of air blown across its surface, possibly below the meltingpoint of PbO. Had this been the case, the ensuing formation of a solid litharge crust wouldhave impeded the oxygen dissolution in the argentiferous lead, thus impairing the finalizationof the refining process. It is worth noting in this regard that Theophilus (1979), in his descrip-tion of the cupellation process, suggests the addition of a small piece of charcoal on top of thelead when it starts to melt, in order to temporarily create a reducing environment, thus inhib-iting the formation of a litharge crust. This operation exhibits a low slagging efficiency andonly ensures (i) the suppression of the more volatile metals and of lead and (ii) the partialremoval of sulphide inclusions and entrapped slag. This process does not appreciably affectthe bismuth inclusions, and the extent to which it can succeed in lowering the copper contentdepends mainly on the initial lead concentration in the metal charge.

The total gold and silver content found in these coins—in excess of 98.7–99%—suggeststhat the metal did not undergo deliberate alloying for hardening or debasement purposes. Theabsence of a supersaturated solid solution of copper in the silver phase tends to confirm thisassertion. The actual precious metal content of the investigated fragments is in accordancewith the elemental composition of archaic Greek coins and higher than that of Hacksilbersamples from the Dor Hoard. The former are believed to consist of unalloyed silver, whilst thelatter have been suspected to be of regulated composition.

As far as the mineral sources for these items are concerned, the following can be observed.It is difficult to assess whether the ubiquitous quartz grains can derive from the smelted ore or


originate, at least in part, from either the casting crucible or the mould material (Notis et al.1984). The distinctive metallographic features of item M1, as compared to the other investig-ated fragments, suggests that at least two different ore sources must have been utilized forthese coins. The phase composition and morphology of M1, exhibiting an unusually high goldlevel with accompanying elemental copper and bismuth inclusions, hints at a polymetallic—possibly jarosite—ore, subjected to a roasting process. Conversely, the observed microstructureof all the other items, implying no detectable bismuth and copper sulphide inclusions withina low-gold metal matrix, is consistent with sulphidic lead ores—possibly from weathered oredeposits—smelted without preliminary roasting or only partially roasted.

As far as the problem of metal recycling is concerned, the following can be observed. It isreasonable to admit that recycling of the metal from inventories and bullion coins, possibly ofdifferent sources, carried out by re-melting and recasting, would result in a substantial loss ofsecond-phase inclusions. The observed inclusions of iron oxide, metal bismuth and coppersulphide in the relevant coins, however, while not allowing a definite conclusion to be drawn,still suggests the idea that primary metal should have been utilized for these issues. Owing tothe unfortunate lack of systematic metallographic investigations on ancient silver artefacts, itis not possible, at this stage, to draw comparative conclusions concerning the microstrustrureof primary and reused metal. Preliminary fractographic data on some mainland Greek coinfragments dating to the fourth century bc only reveal copper sulphide inclusions embedded ina matrix of slightly debased silver.

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