‘GRANITO DEL FORO’ AND ‘GRANITO DI NICOTERA’:PETROGRAPHIC FEATURES AND ARCHAEOMETRIC

PROBLEMS OWING TO SIMILAR APPEARANCE*

F. ANTONELLI,† L. LAZZARINI and S. CANCELLIERE

Laboratorio di Analisi dei Materiali Antichi—DSA—Università Iuav di Venezia, S. Polo 2468, 30125 Venice, Italy

Granitoid rocks were among the stone materials most frequently used for columns and pillarsduring the Roman period. When employed in Rome and the Mediterranean provinces, theywere mainly quarried in Egypt, in Asia Minor and in Italy. Some of these rocks show verysimilar macroscopic features, so it is often very difficult to tell them apart with the naked eye.This is the case with the ‘Granito del Foro’ (or Marmor Claudianum), from the Gebel Fatireh,in the Eastern Desert, and the ‘Granito di Nicotera’ (Calabria), both exploited from the firstcentury AD onwards. Both feature medium grain size and a white-greyish colour with blackpatches. In order to obtain a certain microscopic and geochemical discrimination of theserocks, and to provide the first known petrographic classification of the ‘Granito di Nicotera’,a comprehensive mineralogical, petrographic and geochemical investigation was performedon several samples from the quarry. The results were compared with the corresponding dataknown for Marmor Claudianum in the literature. Good discrimination between the granitesis possible, mainly on the basis of modal mineralogy and geochemical characteristics. The‘Granito del Foro’ contains hornblende, while the ‘Granito di Nicotera’ contains muscovite,and has a distinctive peraluminous index and trace element abundances.

KEYWORDS: GRANITO DI NICOTERA, ANCIENT QUARRIES, PETROGRAPHY,GEOCHEMISTRY, MARMOR CLAUDIANUM, DIFFERENTIATION, ARCHAEOMETRY

INTRODUCTION

During the Roman Imperial era, granites and, generally, granitoid rocks, were widely used in theMediterranean area for ornamental purposes and especially, given their intrinsic good physicaland mechanical characteristics, for columns and pillars. Starting from the first century ad, themain source areas of granitoid rocks were Egypt (Aswan and the Eastern Desert), Asia Minor(northwestern Turkey) and Italy (Nicotera and the islands of Elba, Giglio and Sardinia) (Fig. 1(a)). There were also some extraction sites of local importance, such as Galicia in Spain andFelsberg in Germany.

Some of these rocks show very similar macroscopic features and therefore they are not easilydistinguishable with the naked eye. For example, it is worth quoting cases such as: (i) theso-called ‘Sienite of Aswan’ and (some varieties of) ‘Sardinian granite’ (Galetti et al. 1992); (ii)the Elban and Mysian granites (De Vecchi et al. 2000); and (iii) the ‘Granito del Foro’ (betterknown as Marmor Claudianum) and ‘Granito di Nicotera’, which are granitoids showing similarmacroscopic aspects. Here, we focus on the building stones in the last-mentioned case (iii).

*Received 20 March 2009; accepted 15 October 2009†Corresponding author: email fabria@iuav.it

Archaeometry 52, 6 (2010) 919–936 doi: 10.1111/j.1475-4754.2010.00520.x

© University of Oxford, 2010

Figure 1 (a) A map of the main Roman sources of granitoid rocks. (b) The location of the Mons Claudianus in theEastern Desert of Egypt.

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Marmor Claudianum, exploited from the first century ad, comes from the Eastern EgyptianDesert (Fig. 1 (b)), while ‘Granito of Nicotera’ was extracted from the end of the first century ad,1

in quarries near the small town of Nicotera on the western coast of Calabria (southern Italy; seeFig. 3 below). These two rocks are macroscopically very similar and may easily be mistaken foreach other at first glance, both in hand specimens and ancient constructions, even by experts. Theholotypes typically have a common medium grain size (1.4–2.0 mm) and their colour is a mix ofwhite and grey with black spots (Fig. 2).

In order to differentiate these two lithotypes and to provide essential information and a correctpetrographic classification for the ‘Granito di Nicotera’ from Calabria, we have undertaken acomplete mineralogical–petrographic and geochemical study of several Nicotera quarry samples.The results are presented here and compared with published data for Marmor Claudianum inorder to enable positive discrimination of the lithological provenance.

Geological and historical backgrounds

‘Granito del Foro’ This rock outcrops on the Mons Claudianus, now the Gebel Fatireh, in theEastern Desert (Fig. 1 (b)), a geologically intricate region between the Nile River and the RedSea, where magmatic and metamorphic rocks of a Proterozoic age basement complex areabundant. From about 1000 to 650 Ma ago, the Proterozoic shield in Egypt was the site of smallocean-basin and island-arc orogenic activity (Gass 1977). This period culminated in the suturingof arcs and basins to form a new, mostly continental, area. Associated tectonic elements includeeugeosynclinal sedimentary and volcanic rocks, ophiolite complexes and calc-alkaline orogenicbatholithic granitoids (Greenberg 1981), from which the Mons Claudianus granite was extracted.The prolific intrusions of granite series, ranging in composition from diorite to alkali-feldspargranite, were connected with a widespread low-pressure metamorphism (El Gaby et al. 1990). Acontrasting tectonic environment characterized by the deposition of terrigenous sedimentsinto isolated, fault-bounded basins (Hammamat Group) and intermediate-to-felsic volcanism(Dokhan Volcanics) followed subduction and suturing (Said 1972). In particular, Marmor Clau-dianum belongs to the late Proterozoic (600 1 50 Ma bp; El Gaby et al. 1990) calc-alkalinetonalite to granodiorite series, occurring as autochthonous and parautochthonous intrusive bodieselongated parallel to the regional setting of the enclosing country rocks. They constitute thelargest plutonic masses of the Eastern Desert basement (El Gaby et al. 1990). These intrusivebodies commonly possess marginal zones with well-developed planar foliation; the earlymembers of this series are quartz-dioritic in composition, rich in mafic minerals and stronglyfoliated, whereas the younger members are increasingly more acidic, lighter in colour andcommonly structureless (El Gaby et al. 1990).

We know quite a lot about the Marmor Claudianum (hereafter MC) because of severalarchaeological and scientific expeditions in the area (Peacock and Maxfield 1997 and referencestherein). The quarries are located within a 1.3 km radius of the Roman station in Wadi UmmHussein, at or near the wadi level. About 130 loci, exploited from the first century ad to thebeginning of the third century ad, have been recognized within this area.

The MC holotype, widely exploited in antiquity, is a medium-grained rock with a whitishbackground (due to the presence of plagioclase and quartz crystals) and blackish spots (biotiteand hornblende). Locally, it can show a more or less marked clustering of leucocratic (light) and

1The date derives both from pottery finds and the presence of a monolith of this stone in a local edifice found in the ‘Timpa’ locality (onthe outskirts of Nicotera), dated to the first century ad (Solano 1985a,b).

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mafic (dark) minerals, and therefore a relatively distinct foliation. A slightly different variety—not intensively quarried—showing a characteristic more well-developed foliation was discoveredby Harrell et al. (1999) in Wadi Umm Huyut, not far from the large quarry area of the DjebelFatireh. These authors called this stone ‘tonalite gneiss of the Wadi Umm Huyut’ (hereafterWUHT). Mineralogically, the WUHT is virtually identical to the MC from Djebel Fatireh.Mineralogical–petrochemical analyses and a list of previous studies are provided for the DjebelFatireh granite by Peacock et al. (1994), Brown and Harrell (1995) and Harrell et al. (1999).Furthermore, these two lithotypes are also very similar in macroscopic appearance. However,they can be distinguished by their foliation: dark minerals in WUHT occur mainly in long, wavy

Figure 2 The macroscopic aspects of the ‘Granito del Foro’ and ‘Granito di Nicotera’.

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folia, whereas in MC they occur in shorter, more planar folia and in irregular patches (Harrellet al. 1999).

Huge monolithic columns of Marmor Claudianum are widespread in Roman monumentsthroughout the Mediterranean provinces. These include (Lazzarini 2004, 105; Williams-Thorpe2008) Alexandria (Egypt), Caesarea Maritima (Judea—Israel), Corinthus (Achaea—Greece),Tessalonica (Macedonia—Greece), Rhodus (Asia—Greece), Ephesus (Asia—Turkey), Sabrathaand Leptis Magna (Tripolitania—Libya), Thysdrus (Numidia—Tunisia), Italica and Corduba(Iberia—Spain), Arausio (Gallia—France), some Italian localities (i.e., Reggio Calabria, Teanoand Verona) and especially in Latium (Tivoli, Grottaferrata and Ostia) and Rome, such as inTrajan’s Forum, the Pantheon and the Baths of Caracalla. This granite was also used for tubs andthe bowls of fountains, as in the WUHT labrum found in Porto, near Ostia Antica, now locatedon the road of ‘Fori Imperiali’ (in front of the ‘Basilica di Massenzio’) in Rome, and as slabs forfacing and flooring (e.g., at ‘Hadrian’s Villa’ in Tivoli).

‘Granito di Nicotera’ We know very little about this granitoid rock. The existence of a Romanquarry that was active from the first to the fourth centuries ad was first discovered in the early1970s and then confirmed in the 1980s by Solano (1985a,b). Nevertheless, the remarkablemacroscopic similarity of this Italian grey granitoid to the more famous Egyptian one has neverbeen noticed.

The ‘Granite of Nicotera’ pertains to the Hercynic granitoids of Capo Vaticano promontory(southern Calabria; Fig. 3), which forms part of the so-called Calabrian Arc, an arcuate Alpinebelt linking the Apennines and the Maghrebian chain of Sicily. Along the Calabrian Arc, which

Figure 3 The location of the Roman quarry of Nicotera in the late Hercynian granitoids of Capo Vaticano (southernCalabrian Arc) (modified after Rottura et al. 1991). 1, Kinzigitic gneiss; 2, tonalites (1granodiorites) of Ioppolo; 3,quartz-diorites and tonalites of S. Maria; 4, tonalites of Briatico; 5, tonalites and granodiorites (area ‘a’) of CapoVaticano; 6, two-mica granodiorites; 7, Miocene–Quaternary deposits; 8, faults. The Nicotera quarry was established onarea 2.

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outcrops in the Nicotera region, a segment of the Hercynian chain of southwestern Europe isexposed. The Capo Vaticano promontory consists largely of Palaeozoic and possibly Precambrianbasement terrains. These are very low-grade to granulite-facies metamorphites (Fig. 3, unit 1) andgabbro to granite plutonic rocks. There are also minor Jurassic ophiolite sequences and Mesozoicto Recent cover series (e.g., Scandone 1982; Rottura et al. 1990 and references therein). In thisarea, strongly to weakly foliated calc-alkaline granitoids, intermediate to acid in composition,were emplaced in late Hercynian times (from 295 1 2 to 275 1 5 Ma bp; Borsi et al. 1976; Schenk1980; Del Moro et al. 1986) and were affected by tectonic overprints of Alpine or Apennineage (Schenk 1989; Rottura et al. 1991). They consist predominantly (65–70 vol%) of biotite-dominated tonalites (Fig. 3, units 2–5) and subordinate (30–35 vol%) porphyritic granodiorites(Fig. 3, units 5a and 6), with unusual alumino-silicate phases (Rottura et al. 1991). The tonalitesmay be strongly foliated in the northern and southern part of the promontory (e.g., the Briatico,S. Maria and Ioppolo–Nicotera tonalites; Fig. 3, units 4, 3 and 2; Rottura et al. 1989, 1990).

Granodioritic and tonalitic rocks (Fig. 3, units 2 and 5), closely associated in space and time(Rottura et al. 1989), share many compositional characteristics, such as their peraluminouscharacter, which are weaker for the tonalites and stronger for the granodiorites, their isotopicsignatures, and the shape of their REE patterns and hygromagmatophile element distributionpatterns (Rottura et al. 1991). These features combine to suggest a close genetic linkage betweenthe intermediate and acidic rocks (Rottura et al. 1991). Nevertheless, the large variations in manygeochemical parameters, such as their Sr, Ba, Rb and Zr contents, even within individual intrusivebodies, make it difficult to infer a derivation of all the granodiorites from the associated inter-mediate tonalites (Rottura et al. 1990, 1991). The analytical data are better explained by assum-ing, as the dominant mechanism, a mix of a crustal acid melt and a component that may have beenderived from the tonalites by fractional crystallization or assimilation and fractional crystalliza-tion (Rottura et al. 1991). Such an involvement of crustal material in the genesis of the CapoVaticano granitoids may be responsible for the many common compositional characteristicsobserved in the intermediate and acidic rocks (Rottura et al. 1991). It may also explain theoccurrence of some unusual Al-silicates, such as sillimanite, as mineral phases supplied from therestites (immobile parts of migmatite metamorphic rocks; Caggianelli et al. 1991).

THE NICOTERA GRANITE QUARRY

The Nicotera granite was not apparently exploited prior to the Roman period (Solano 1985a,b).The Roman quarry, locally called ‘Petti Agnone’, was opened at 60 m above sea level on thesouthwestern slope of the Poro Massif, just above the ancient Roman harbour of Nicotera (Fig. 3,unit 2). The quarry is now a very difficult place to reach, since it has been almost entirely coveredby a landslide. Despite this, it is still possible to observe many unfinished column shafts andsquared blocks on site (Fig. 4), as well as large and small deposits of debris. The extension of thequarrying area can be estimated as about 2500 m2, while the largest extracted and visiblemonoliths are columns with a length of 5.5 m and a diameter of 0.7 m.

The quarry was partly excavated in the 1970s by a team of archaeologists (Solano 1985a,b),who reopened about 200 m2 of the original area. In sector A, delimited by a 3.80 m-long wall, theteam discovered: six semi-finished columns with upper shafts, varying from 5.30 to 5.73 m longand from 2 to 0.37 m in diameter; one parallelepipedal block measuring 1.82 ¥ 0.27 m; oneroughcast lintel, 1.77 ¥ 0.40 m; and one roughed-out basin, maximum diameter 0.75 m, mouth0.65 m, rim 0.10 m, height 0.26 m and depth 0.15 m. In sector B, 15 semi-drafted artefacts werediscovered, including: four fragments of column shafts (including two with upper scape); 10

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parallelepipedal blocks, varying from 2.26 to 1.30 m in length; and one basin, with its centreshaped into a roughly concentric circle (Ø = 0.54 m), and measuring as follows: maximumdiameter 1.92 m, mouth 1.52 m, rim 0.40 m, height 0.35 m and depth 0.25 m. Sector C contained:five fragments of column shafts, with upper scape, with lengths varying from 2.45 to 1.34 m; oneparallelepipedal block of a lintel, measuring 2.30 ¥ 0.36 m; and eight semi-finished quadrangularcrustae, measuring 1.40 ¥ 0.70 ¥ 0.45 m.

From the pottery finds, it has been possible to date the beginning of the quarry activity to thefirst century ad (Solano 1985a,b). It is very likely that the exploitation continued to some extentin the following centuries, and came to an end in the fourth century (as suggested by a coin foundin sector C of the quarry; Solano 1985a). This may have occurred in ad 369, when damage froma strong earthquake (mentioned by the writer Orosius in his Historiarum adversus paganos, IV,4) caused the harbour and the residential area of Nicotera to be abandoned.

SAMPLING AND ANALYTICAL METHODS

Eighteen samples from different sectors of the Nicotera quarry, and from unfinished columnshafts and squared blocks found in the quarry, were collected (Table 1) for petrographic andgeochemical characterization. Care was taken to sample rock in a fresh state and in its mostrepresentative facies.

Petrographic analysis on thin sections was carried out under the polarizing microscope andmodal mineralogy evaluated by means of a point counter, with at least 2000 points counted per

Figure 4 Several views of the Roman quarry of Nicotera, showing a part of a quarry front with close parallel groovesand many abandoned column shafts.

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section (integrated area ~200 mm2). All of the samples were also subjected to quantitativechemical analysis by XRF: whole-rock analyses for major, minor and trace element contentswere carried out on beads prepared by melting powdered samples with lithium tetraborate(Li2B4O7). Intensities were calibrated in accordance with Falcone et al. (1998): the precision ofthe method is between 1% and 5% for major and minor elements, and better than 20% for traceelements.

ANALYTICAL RESULTS

Petrographic characteristics

The modal mineralogical data (Table 2) and the petrographic studies on the MC (Kraus andRöder 1962; Greenberg 1981; Galetti et al. 1992; Brown and Harrell 1995; unpublished data) andthe Calabrian ‘Granito di Nicotera’ show that both are medium- to coarse-grained rocks. They arecomposed mainly of intermediate plagioclase, quartz and biotite, with or without hornblende. Ona quartz – alkali feldspar – plagioclase, or QAP, diagram (Le Maitre et al. 1989), they may beclassified as tonalites (Fig. 5). In a few cases, some samples can be classified as tonalitic–granodioritic gneiss with a moderate foliation; these are samples 7, 13 from Nicotera and asample from the Mons Claudianus reported by Galetti et al. (1992).

In particular, the ‘Granito di Nicotera’ consists of euhedral zoned oligoclase (An32–25) plagio-clase (42–58 modal %), quite large in size (up to 5 mm), somewhat aggregated in clusters(synneusis) and poikilitic; quartz (20–40 modal %) up to 3.5 mm in size, forming anhedral zoneswith consertal microstructure (irregularly shaped crystals closely interlocking without interstitialspaces); medium to large (up to 4.5–5.0 mm) brown flakes of subhedral 1 anhedral biotite (7–19

Table 1 A list of the samples collected from different sectors of theNicotera quarry, and from unfinished column shafts or squared blocks

present in situ

Sample number Provenance-location within the quarrying area

1 Quarry front: right side, half height2 Unfinished column shaft from sector C3 Unfinished column shaft from sector B4 Unfinished column shaft from sector A5 Unfinished column shaft from sector C6 Ancient squared block from sector B7 Semi-buried unfinished column from sector A8 Ancient squared block from sector B9 Quarry front: right side, half height

10 Quarry front: low portion of the central side11 Quarry front: low portion of the left side12 Quarry front: low portion of the right side13 Semi-buried unfinished column from sector A14 Flake of the ancient debris from sector C15 Quarry front: low portion of the central side16 Quarry front: left side, half height17 Quarry front: central side, half height18 Quarry front: right side, half height

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Table 2 Modal mineralogy—average values for the quarry samples. ‘Granito di Nicotera’: present study.‘Granito del Foro’, data from: Kraus and Röder (1962) (one thin section); Greenberg (1981) (mean of four thin

sections); Galetti et al. (1992) (one thin section); Brown and Harrell (1995) (mean of six thin sections); present study,one thin section

‘Granito del Foro’ (%) ‘Granito di Nicotera’ (%)

Plagioclase 53.8Oligoclase

51.6Oligoclase

Quartz 26.2 29.1K-feldspar perthite, microcline 1 orthose 2.1 2.5Hornblende 8.2 Absent or <1Biotite 8.8 12.0Muscovite Absent 1.2Accessories 0.9

Sphene + apatite + oreminerals

3.6Allanite + sillimanite + sphene + apatite + oreminerals

Number of thin sections 13 18Average number of points counted 2000 2000

Figure 5 The petrographic classification of ‘Granito di Nicotera’and ‘Granito del Foro’(*, present study) following theQAP modal diagram (Le Maitre et al. 1989).

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modal %), locally chloritized and including zircon; subhedral to anhedral or interstitial crystals(0.6–2.9 mm in size) of perthitic microcline 1 orthoclase (1–5 modal %); and rare muscovite(traces to 2.5 modal %), generally interstitial, but also occurring in small needle-like aggregateswith biotite. Allanite, sphene, apatite, opaque minerals—including ilmenite—and minor silli-manite are the common accessory phases. The microscopic investigation shows that the granitoidrocks from the Nicotera quarry only very rarely contain hornblende; in fact, amphibole occurs injust two samples (nos. 2 and 12), but its presence never attains 1 modal %.

The MC data summarized by Brown and Harrell (1995) integrated with results obtainedthrough the microscopic study of an additional quarry sample (Table 2) show that this tonaliteand tonalitic gneiss consist of oligoclase plagioclase >> quartz >> hornblende + biotite >> K-feldspar (mainly microcline) >> accessory minerals (apatite, magnetite, sphene and zircon).Apart from microcline and accessory minerals, all of the above phases show crystals mostly from1 mm to 3.5 mm. Aggregates of hornblende and biotite intergrowths are abundant and can attainsizes of up to 1 cm across.

Whole-rock geochemistry

According to the geochemical and petrological descriptions provided by Rottura et al. (1989,1991) for the granitoids of the southern Calabrian Arc, ‘Granito di Nicotera’ shows both a generalcalc-alkaline composition and a weakly peraluminous affinity (Table 3; Fig. 6). In fact, most ofthe analysed samples fall within the range of TiO2 and Sr compositions defined by these authorsfor the calc-alkaline tonalites and granodiorites of the region (Fig. 6), and all of them exhibit aperaluminous index [PA.I = molar Al2O3/(CaO + Na2O + K2O) ratio] slightly 31 (as well ascontaining Al-silicates and two micas, with biotite >>> muscovite). On the contrary, analysisshows all the MC samples to be fairly metaluminous (peraluminous index < 1; Table 3).

The modal mineralogy data closely matches the chemical results given by the classificationdiagram of De La Roche et al. (1980) (Fig. 7 and Table 3), based upon the cation proportions,expressed as millications (cationic proportions ¥ 1000), in which our samples again proved to bemainly tonalites. This diagram avoids the criticism that wt% oxide data do not faithfully reflectthe cation distribution of a sample, and its main advantage is that the entire major elementchemistry of the rock is used in the classification. The nomenclature of the rocks is consistentwith that utilized in the QAP diagram of Figure 5. The degree of silica saturation and changingfeldspar compositions can be shown. Unfortunately, this provides a general classification, anddoes not allow an unambiguous distinction between Egyptian and Calabrian lithologies. Never-theless, using this petrochemical classification scheme, two semi-buried column shafts, samples7 and 13 from Nicotera, fall more correctly within the granodiorite field (Fig. 7). These samplesare differentiated by enrichment in quartz, 37–40 modal %, and muscovite, about 2.5 modal %,and are poorer in biotite, about 7 modal %, and high L.O.I. values.

The rocks from Nicotera range in composition from intermediate to acidic, with an SiO2

content of 60.8–72.9 wt%, and varying from 60.8 to 68.8 wt% if the leucocratic samples 7 and13 are excluded. The major and most of the trace elements display quite regular variation, withnegative correlation trends on Harker diagrams. However, Zr (95–162 ppm) and Sr (225–318 ppm) do not exhibit any significant trend with silica and their contents are, on average,homogeneous. The Ni content is constantly lower than 10 ppm. The Rb abundances range from44 to 96 ppm and, as stated by Rottura et al. (1991) for the Capo Vaticano granitoids, they aresomewhat lower than those typically found in Phanerozoic orogenic granites (e.g., Pearce et al.1984).

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Tabl

e3

Che

mic

alda

tafo

r‘G

rani

todi

Nic

oter

a’(p

rese

ntst

udy)

,‘G

rani

tode

lF

oro’

(no.

LG

3fr

omG

alet

tiet

al.1

992;

nos.

MC

1an

dM

C2

from

Bro

wn

and

Har

rell

1995

;no

.MO

C2

from

Pea

cock

etal

.199

4)an

dgr

anit

oid

colu

mns

from

the

thea

tre

ofTe

ano

and

the

cath

edra

lof

Mil

eto.

PA.I

.=pe

ralu

min

ous

inde

x

Sam

ple

Gra

nito

diN

icot

era

Gra

nito

del

For

oC

olum

nfr

omth

eT

heat

reof

Tean

oM

ilet

oC

athe

dral

12

34

56

78

910

1112

1314

1516

1718

LG

3M

C1

MC

2M

OC

2T

1T

3T

4M

IL1

wt%

SiO

262

.42

63.0

161

.63

68.0

060

.84

63.2

172

.91

61.5

062

.27

68.4

461

.76

66.2

371

.13

63.0

961

.62

64.3

466

.84

65.5

965

.68

62.9

065

.90

64.3

466

.35

65.1

364

.39

62.3

1T

iO2

0.64

0.63

0.71

0.42

0.74

0.65

0.43

0.69

0.67

0.50

0.73

0.54

0.27

0.61

0.66

0.62

0.50

0.56

0.57

0.59

0.62

0.71

0.60

0.68

0.51

0.49

Al 2

O3

18.2

218

.54

18.6

716

.89

18.9

218

.09

13.6

518

.85

18.6

416

.29

18.7

216

.54

16.0

718

.76

18.9

517

.46

16.9

217

.19

16.2

115

.70

16.1

016

.19

16.0

716

.60

16.6

919

.72

Fe2O

35.

194.

905.

363.

185.

384.

883.

345.

495.

283.

645.

364.

652.

264.

535.

164.

713.

714.

213.

823.

913.

704.

864.

104.

274.

223.

90M

nO0.

090.

080.

090.

060.

090.

090.

060.

110.

090.

060.

090.

060.

040.

080.

090.

060.

050.

060.

070.

070.

070.

070.

060.

060.

070.

07M

gO2.

432.

332.

561.

402.

522.

261.

572.

532.

501.

592.

552.

090.

922.

122.

282.

311.

882.

092.

072.

021.

912.

291.

902.

042.

151.

83C

aO5.

315.

285.

405.

095.

485.

214.

084.

904.

944.

505.

234.

614.

605.

435.

325.

075.

035.

054.

794.

894.

474.

664.

514.

454.

316.

27N

a 2O

3.24

3.06

3.14

3.38

3.44

3.29

2.44

3.26

2.99

2.99

3.32

3.30

3.32

3.31

3.43

3.15

3.23

3.19

4.39

3.97

4.84

4.25

4.50

4.56

3.82

3.66

K2O

2.24

2.03

2.25

1.42

2.37

2.15

1.41

2.49

2.39

1.85

2.03

1.85

1.30

1.92

2.28

2.14

1.72

1.93

1.65

1.57

1.77

1.81

1.55

1.82

3.29

1.58

P 2O

50.

300.

160.

180.

150.

200.

170.

110.

190.

220.

140.

220.

120.

080.

150.

210.

140.

120.

130.

190.

180.

180.

230.

200.

220.

240.

16L

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130.

320.

480.

330.

460.

320.

810.

660.

360.

300.

500.

260.

870.

190.

160.

480.

620.

520.

590.

600.

750.

490.

130.

160.

150.

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1.05

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1.04

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1.05

1.05

1.08

1.07

1.04

1.04

1.04

0.91

0.92

0.89

0.93

0.93

0.95

0.94

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ppm

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7381

5687

9651

9286

6977

6344

6693

7863

7023

6050

3834

3711

616

0Sr

293

295

294

281

298

280

225

276

286

276

298

268

293

304

282

304

318

311

620

780

640

638

602

637

700

368

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399

109

6194

9864

108

101

6995

9347

9095

9270

8185

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7988

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3925

3928

2424

3332

2927

2830

2827

2829

2527

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3236

3175

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8583

8455

8682

5512

188

6310

472

4175

9380

6572

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6670

5310

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r12

512

114

013

513

013

695

142

115

115

111

139

103

111

128

162

152

157

184

300

310

310

9111

612

915

7

‘Granito del Foro’ and ‘Granito di Nicotera’ 929

© University of Oxford, 2010, Archaeometry 52, 6 (2010) 919–936

As regards MC, the few chemical analyses reported in the literature (Galetti et al. 1992;Peacock et al. 1994; Brown and Harrell 1995) indicate a fairly acidic rock that, compared withNicotera samples with similar silica content, displays a relative depletion in Fe2O3, K2O, Ba(1Rb), and higher abundances of Na2O and Sr (1Ni; Table 3). These seem to be useful geochemi-cal markers.

DISCUSSION

Following the analytical results, we can infer that the Nicotera Roman quarry was opened in anarea characterized by the prevailing presence of calc-alkaline slightly peraluminous tonalites(‘Tonalites of Ioppolo’; Fig. 3). Locally, some more differentiated/leucocratic rocks, geneticallylinked to the tonalite, also outcrop here. In fact, as observed by Rottura et al. (1990), themultipulse calc-alkaline bodies of the Capo Vaticano promontory (Fig. 3) are zoned, both tex-turally and compositionally, from strongly foliated tonalite in the northern margin to weaklyfoliated/unfoliated granodiorite–tonalite towards the interior and the south.

From an archaeometric point of view, the granitoids can be distinguished from each otherwithout difficulty by an accurate study in thin section (Fig. 8 and Table 2), due to the constant andsignificant presence of hornblende in the MC (Figs 8 (a) and (b)), and of muscovite (Figs 8(d)–(f)), sillimanite (Figs 8 (f) and (g)) and allanite (Fig. 8 (h)) in the tonalites from Nicotera,

Figure 6 SiO2 variation diagrams showing the calc-alkaline tonalite and granodiorite fields defined by Rottura et al.(1989) for granitoids of the southern Calabrian Arc. Except for the more leucocratic samples 7 and 13 (which show thehighest L.O.I. values on Table 3), the ‘Granito di Nicotera’ (black dots) falls mainly within the fields.

930 F. Antonelli, L. Lazzarini and S. Cancelliere

© University of Oxford, 2010, Archaeometry 52, 6 (2010) 919–936

whereas, by contrast, hornblende is absent or very rare. The distinction is also confirmed bytextural features. The Marmor Claudianum shows an equigranular hypidiomorphic texture. Bycomparison, the ‘Granito of Nicotera’ features a heterogranular hypidiomorphic texture that islocally pseudoporphyric, and characterized by consertal quartz (Fig. 8 (g)) and reabsorptionphenomena affecting most of the crystals.

In addition to petrographic studies, the chemical composition of major and trace elements alsoprovides a good distinction between the Egyptian and Calabrian granitoid rocks. In particular, theperaluminous index [Al2O3/(CaO + Na2O + K2O)], Na2O and Sr (1Ba, Zr and Ni) contents are themost discriminating chemical parameters (Fig. 9 and Table 3).

As regards the utilization of ‘Granito di Nicotera’, many regional examples are known: forinstance, the columns reused in front of the church of S. Eufemia Vetere (Lamezia, Calabria)(h = 113 cm; Ø = 34 cm) and in the old Romanesque (ad 1081–6) cathedral of Mileto (ViboValentia, Calabria), and now in the local museum (h = 295 cm; Ø = 40 cm). A petrographic studyof a thin section obtained from the column of S. Eufemia Vetere and the geochemical investiga-tions conducted on the Mileto stone2 (Figs 8 (i) and 9, and Table 3) show that they are made ofa tonalite with very similar compositional and textural features to those described for the ‘Granitodi Nicotera’. In fact, in the first case, the rock has a heterogranular hypidiomorphic texture, islacking in hornblende and features the presence of muscovite, allanite, sillimanite and consertal

2The considerable alteration of the sample from S. Eufemia Vetere made geochemical analyses impracticable; and the small size of thesample from Mileto did not allow the preparation of a thin section.

Figure 7 The petrochemical classification of the analysed samples according to De La Roche et al. (1980).R1 = 4Si - 11(Na + K) - 2(Fe + Ti); R2 = 6Ca + 2Mg + Al; R1 and R2 are calculated from cationic proportions ¥ 1000(millications).

‘Granito del Foro’ and ‘Granito di Nicotera’ 931

© University of Oxford, 2010, Archaeometry 52, 6 (2010) 919–936

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932 F. Antonelli, L. Lazzarini and S. Cancelliere

© University of Oxford, 2010, Archaeometry 52, 6 (2010) 919–936

1.3

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‘Granito del Foro’ and ‘Granito di Nicotera’ 933

© University of Oxford, 2010, Archaeometry 52, 6 (2010) 919–936

quartz (Fig. 8 (i)). In the second case, sample from Mileto shows a peraluminous index >1 as wellas similar values of major and trace elements, especially low Na2O (3.66%) and Sr (368 ppm; cf.,Fig. 9), with respect to the quarry rocks (Table 3).

By contrast, the columns of the Roman theatre of Teano, in Caserta, Campania, constructed inthe second century bc, and rebuilt and embellished in the second century ad, might have beenmade of ‘Granito di Nicotera’ (Fig. 10). However, petrographic and geochemical analyses showthat they originated from the Mons Claudianus (Table 3; Figs 8 (c) and 9). The rock has aequigranular hypidiomorphic texture, an abundance of hornblende (7.5–8.8 modal %), a generallack of muscovite and sillimanite, and high Na2O (3.82–4.56 wt%) and Sr (602–707 ppm)contents.3

CONCLUSIONS

This paper provides a mineralogical–petrographic and geochemical characterization of the grani-toid rock of the Nicotera region (Calabria), for which there is evidence of ancient quarryingduring the Roman age. The results of this characterization are compared with published data forthe well-known ‘Granito del Foro’ (Marmor Claudianum), an Egyptian granitoid rock that is verysimilar in macroscopic appearance to the ‘Granito di Nicotera’. The petrographic features, andmajor and trace elements studies, provide a clear source discrimination. These include thepresence or absence of hornblende, muscovite, allanite and sillimanite, as well as differentabundances of Na2O, K2O, Sr and a peraluminous index.

3The archaeological sample T4 shows a very high and anomalous content of Ba (1277 ppm) compared to the other samples from Teano,as well as those from Mons Claudianus. Most probably, this was due to the small size of the flake sampled, which had very few maficminerals and a greater proportion of quartz and coarse-grained feldspar. As is well known, K-feldspar normally contains significantamounts of barium.

Figure 10 Teano (Caserta, Campania), the open air deposit of the Roman theatre, showing the columns made of‘Granito del Foro’ considered in this study.

934 F. Antonelli, L. Lazzarini and S. Cancelliere

© University of Oxford, 2010, Archaeometry 52, 6 (2010) 919–936

Ongoing aspects of this research will include a verification of the use of ‘Granito di Nicotera’in the ancient Roman monuments of Italy, in order to identify any possible confusion with themore famous Marmor Claudianum. Although huge monolithic columns, such as those of Trajan’sForum, could not have been quarried at Nicotera, and are definitely made of Marmor Claudianum(cf., Williams-Thorpe et al. 1996; Williams-Thorpe 2008), the granite of Nicotera might havebeen used for medium- and small-sized shafts. We suspect a significant extra-regional distributionof such columns, and some exports to Rome.

ACKNOWLEDGEMENTS

The authors wish to express their sincere thanks and gratitude to Professor J. K. Greenberg andA. Rottura for their helpful provision of geological and petrographic information on Egyptianand Calabrian granitoid rocks, respectively. We are grateful to Dr A. Solano for his generoushelp during the fieldwork on the Nicotera quarry, and to Professor A. Renzulli for his criticalassessment of the first draft of the text. Many thanks are due to the anonymous referees for theirextremely precious work.

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936 F. Antonelli, L. Lazzarini and S. Cancelliere

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