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ABSTRACTThe paper presents a short history of use and a minero-petrographic char-acterization of six important coloured stone types originating from Asia Minor (Turkey) much used by the Romans in all the provinces of their Empire as decorative stone, mostly for opera sectilia and columns. Two of these stones, marmor troadense from Çigri Dâg (Ezine) and marmor mysium from Kozak (Bergama) are granitoids. Two are metamorphites: marmor iassense from Iasos (Kiykislacik, Mylas) and marmor lucullaeum from Teos (Sigacik, Izmir), and two are sedimentary rocks: marmor sagarium, an oligomictic breccia from Vezirhan (Bilecik), and marmor triponticum, a rudist limestone from Kutluca (Izmit). Distribution maps and the main morphologies, causes and mechanisms of deterioration are presented and discussed.

ÖZETBu çalışma Anadolu’dan çıkan altı önemli renkli taş türünün kısa kullanım tarihçesini ve minero-petrografik tanımlanmasını anlatır; bu taş türlerini Romalılar imparatorluğun bütün eyaletlerinde özellikle opera sectilia ve sütunlarda dekoratif taş olarak yaygın biçimde kullanmışlardı. Bu taşlardan Çiğri Dağ’da (Ezine) çıkan marmor troadense ve Kozak’ta (Bergama) çıkan marmor mysium granit benzerleridir. İasos’tan (Milas) çıkan marmor iassense ve Teos’tan (Sığacık, İzmir) çıkan marmor lucullaeum metamor-fittir. İkisi çökelti kayasıdır: Vezirhan’da (Bilecik) çıkan oligomiktik breş marmor sagarium ve Kutluca’da (İzmit) çıkan bir kireçtaşı olan marmor triponticum. Dağılım haritaları, ana morfolojik özellikler, bozulma neden ve mekanizmaları sunulmakta ve tartışılmaktadır.

INTRODUCTIONIt is well known how much the Romans from Republican to Late Imperial times liked to decorate their public buildings and private houses with the most beautiful coloured stonework they found and quarried in all the conquered provinces of their Empire. The use of ornamental stone for columns and opera sec-tilia, and more rarely for statuary in fact, became an important status symbol for the rich and a means of propaganda for the emperor, his family and the dominant classes. In many cases, it also assumed symbolic meanings, as for example in the case of Egyptian porphyry which, because of its purple colour, was used for the official portraits and sarcophagi of Roman and Byzantine emperors. The fame attached to many types of stone during these two empires continued throughout the medieval period in the East and West and on into Renaissance and Baroque periods in Europe, when these same stones were widely plundered from ancient monuments and re-used in churches, mosques and palaces. Several ‘antique marbles’ were re-discovered towards the end of the nineteenth century, and their quarries were re-opened; some of them are still available on the marble market.

A similar history of usage applies to six important col-oured types of stone which the Romans quarried in Western Asia Minor (present-day Turkey) and distributed all over the Mediterranean and beyond, sometimes reaching such distant provinces as Britannia to the West, and the interior of Syria to the East. These are two granitoid rocks, marmor troadense from Troas, and the granite from Kozak (Mysia); two metamorphites, marmor iassense, or carium, from Iasos (Caria), and marmor lucullaeum from Teos (Ionia); and two sedimentary rocks, marmor sagarium and marmor triponticum from Bithynia.

This paper considers the provenance, a short history of use, distribution, basic scientific characterization and deteriora-tion morphologies and mechanisms for all these stone types, in the hope of contributing to our overall knowledge of these materials and to their conservation in ancient monuments and archaeological areas.

The collection of information on the subjects just described involved, on one hand, a thorough study of the existing spe-cialist literature, visits to relevant ancient quarries and of a large number (over 400) archaeological sites and monuments to check for the occurrence of these stone types studied here so as to prepare distribution maps. These report the presence in primary contexts (Roman and Byzantine) and in secondary ones (Medieval or later).

On the other hand, research was continued in the laboratory using standard minero-petrographic analyses on thin, polished sections made with a polarizing microscope, supplemented by X-ray diffraction analysis (XRD) and observations in the scanning electron microscope (SEM) equipped with an energy-dispersive spectrometer (EDX) for chemical analyses. These were performed on samples collected in the ancient quarries of each stone type and on several Mediterranean monuments in which the same stones were used. Porosimetric measurements by mercury-intrusion were also made on selected samples of some of the stone types discussed.

THE SIX COLOURED STONE TYPES: HISTORY OF USE, QUARRIES AND DISTRIBUTION, PETROGRAPHIC CHARACTERISATIONThe two granitoids mentioned were used early on as building materials in the ancient Greek towns around their quarries, such as Alexandria Troas and Neandria for marmor troadense [1, 2], and Perperene and Pergamum for the Mysian granite [3]. They were both discovered later by the Romans and much used as prized materials at the end of the first century ad. They were also exported as semi-worked columns and pillars at the begin-ning of the following century as demonstrated by their presence in the Villa Adriana at Tivoli (Rome). Both types were more rarely employed as facing slabs, and locally only for sarcophagi and tubs.

The granite from the Troas, marmor troadense, called granito violetto by the Roman stonemasons of the Baroque period because of its somewhat violet hue (Fig. 1a), is the most important granitoid of Classical antiquity as demonstrated by the distribution map for this material (Fig. 2a) [4, 5] mostly employed for columns and showing remarkable popularity in all the provinces of the Empire. Important examples of its use are the columns of the Trajan Temple, and of Santo Stefano Rotondo (Rome), and those of St Nicola, Bari and of Cefalù Cathedral. It was produced by numerous quarries on the slopes of the Çigri Dâg in the province of Ezine [6], and columns were shipped from the nearby harbour of Alexandria Troas (now Dalyan). The stone may be classified petrographically as a quartz-monzonite [2, 7] formed by an equal amount of violet K-feldspar (in porphyroblasts often of 2–3 cm across) and white oligoclasic plagioclase, of black hornblende and biotite with grey quartz (Fig. 3a).

The granite from Mysia was named marmor mysium by the present author (in accordance with the Roman practice of denominating stone with geographical names) [8], who dif-ferentiated it first from the very similar granite from the Island of Elba (Italy), and discovered its quarries in the area of the Kozak Dâg, in the territory of the ancient town of Perperene and very close to Pergamum, where it was extensively used in Roman times. This stone is a grey, fine-grained granodiorite

SIX COLOURED TYPES OF STONE FROM ASIA MINOR USED BY THE ROMANS, AND THEIR SPECIFIC DETERIORATION PROBLEMS

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(Fig. 1b); it was less sought after than the granito violetto, and so much less widely distributed in the ancient Mediterranean area (Fig. 2b). Notable examples are the columns of the ‘édifice à col-onnes’ of Carthage, of the temple of Venus at Djemila (Algeria), of the ‘Tempietto del Bramante’ (Rome), the obelisk of ‘Place de la République’ at Arles (France), and so on. This stone con-tains the same minerals as those seen in the previous granitoid, but with the proportions of a typical granite/granodiorite; an important feature is the presence of small amounts of prismatic crystals of black hornblende (3–8 mm across) (Fig. 3b), which helps in distinguishing this stone from the Elba granite where this mineral is missing [9].

The two metamorphites have quite different history of use compared to the granitoids, and to each other. Marmor iassense, or carium, called cipollino rosso by the Roman stonemasons of the Renaissance period for its appearance similar to a sliced red onion, in fact was used not only for columns and facing slabs, but also in a variety with a uniform deep red colour [1, 10], for small objects and statuary. In this latter case it was prob-ably being used as a substitute for the more famous marmor taenarium (rosso antico) from Peloponnesus. The two more common varieties, the veined and brecciated ones show a dark red ground with white and grey veins and clasts respectively (Fig. 1c). The ancient quarries are close to the Greek-Roman town of Iasos (partly below the site of the village of Kiykislacik, in the province of Mylas), from which this beautiful stone started to be used locally in the Hellenistic period, and exported towards the West (see Fig. 2c), in the Severan period, reaching its great-est use in Proto-Byzantine times. Remarkable examples of the most common veined variety are the columns in the interior of the Dome of the Rock of Jerusalem, those of St John at Ephesus, and the wonderful wall facing slabs in the interiors of Aghios Demetrios, Thessaloniki. It is also used at San Vitale, Ravenna, and at Saint Mark’s in Venice. All varieties of cipollino rosso are classifiable as impure, calcitic marbles (Fig. 3c), coloured by haematite, with an insoluble residue of quartz, plagioclase chlorite, and sericite reaching proportions of 7–12%.

Marmor luculleum took its name from the consul M.L. Lucullus, but is better known as africano because of its black ground. Being a conglomerate it was not easily sculpted and was hence used only seldom for the busts of imperial portraits. It is a very attractive stone featuring pinkish white, sometimes blood-red, angular clasts (Fig. 1d), well distinguished on a ground that may also be dark green in colour. Because of its beauty, it appears in Diocletian’s Edictum de Pretiis (ad 301) as the third most expensive stone after the two porphyries and marmor doci-menum from Phrygia. It enjoyed great success from the middle of the first century bc to the end of the second century ad (Fig. 2d), when in the quarries, situated near ancient Teos, now the village of Sigacik (south west of Izmir), all the breccia was completely worked out. Notable examples of this breccia are the columns of the Basilica Emilia, and of Santa Cecilia, the threshold of the Pantheon in Rome, the many columns used in the frons scenae of the theatres of Arles and Orange (France), Sessa Aurunca and Velia (southern Italy), and elsewhere. The stone quarried later was a rough grey material (Fig. 1d), of little appeal. The total amount of stone quarried at Teos was enormous, and the space previously occupied by a hill is now a lake, the Kara Göl [1, 11]. Africano may be classified as a calcareous meta-breccia. It is in fact mostly made of calcitic (sometimes slightly dolo-mitic), micritic clasts more or less coloured by haematite, in a cement also made of micrite often containing quartz, chlorite (responsible for its green colour), and sericite (Fig. 3d). These all deriving from the metamorphism of clay-like impurities in the pre-metamorphic sedimentary conglomerate.

A similar, purer non-metamorphic breccia is marmor sagar-ium, a stone taking its name from the river Sagarios along which the ancient quarries lay. These are in fact very close to the village of Vezirhan, in the province of Bilecik, and in a region known as Bithynia in Roman Times [1, 12]. This stone was called breccia corallina by the Roman stonemasons, and is now on the market as ‘Rosalia’. It is a true calcareous breccia, poorly sorted and with angular or sub-rounded clasts of centimetric to metric size, embedded in a coral-coloured cement (Fig. 1e). It was probably quarried until the end of the fourth century ad. This breccia was used from the Augustan age for opera sectilia, columns and tubs that reached Roman, mainly, sites of the eastern and central parts of the Mediterranean basin (Fig. 2e). Italian examples of

Fig. 1 Macroscopic appearance of the six stone types studied (left to right, top to bottom): a) marmor troadense. b) marmor mysium. c) marmor iassense. d) marmor luculleum. e) marmor sagarium. f) marmor triponticum.

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this stone include the columns in the Baptistry of Aquileia, and those once in the theatre of Pavia, now in the local archaeologi-cal museum; in Turkey, there are many in Izmir and Ephesus, and North African examples include those in Sabratha and Leptis Magna (Libya). The study of thin sections enables it to be classified as a dismicrite (Fig. 3e) [13], that is to say a very pure limestone formed from the lithification of fine calcitic mud deposited in an ancient lagoon. The pinkish-rose colour of the cement is due to more or less concentrated haematitic particles.

The sixth stone also came from Bithynia, and is a Cretaceous sedimentary rock. This is the marmor triponticum of the Romans [1, 12], also called occhio di pavone by Italian stonecutters from its texture recalling the appearance of a peacock’s tail as shown by the holotype. There exist several colours for the back-ground of this stone, the most important and common being red

(Fig. 1f ), where the circular cross-sections of rudists, a fossil-ized bivalve, can be clearly seen. Various other varieties exist with a rose, beige or brown ground and more or less preserved fossil sections, sometimes much fragmented. This stone was quarried from the beginning of the third century ad in the area of Kutluca, province of Izmit, not far from the ancient road con-necting Costantinopolis to Nicomedia, from where it spread all over the eastern and central Mediterranean (Fig. 2f), especially in the Early and Middle period of the Byzantine Empire. Notable occurrences are the columns of the Christian Basilica by the Sea of Corinth (Greece), the facing slabs of the Kariye Camii in Istanbul, and the many extraordinary columns from Carthage re-used in the prayer room of the Zeytun Mosque in Tunis. Petrographically it is a rudist limestone variously pigmented by haematite (red and rose varieties) or limonites (beige and brown

Fig. 2 Maps of distribution of the six coloured stone types, updated to 2009. For the identification of the localities indicated with numbers, see the Ap-pendix of the book titled Poikiloi Lithoi . . . [5].

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varieties) (Fig. 3f), sometimes slightly marly (for example, with small amounts of illite/montmorillonite in the cement).

THE DETERIORATION OF THE SIX STONE TYPES: MACRO- AND MICROMORPHOLOGIES, CAUSES AND MECHANISMSThe deterioration of the stone types considered above, as for all other stones, obviously depends on their intrinsic physico-

chemical characteristics, that is, fabric and texture, mineralogi-cal/chemical composition and porosity [14]. According to these features, the six lithotypes may be grouped somewhat differently than before. The two granitoids can be considered together, as well as the two breccias, while the marble and the fossiliferous limestone behave differently.

The granito violetto and the misio are very similar both in their massive texture and granular fabric, and also compare closely in their mineralogical and chemical composition. The most common macromorphologies observed in Roman columns in various environments, but mostly in ancient Mediterranean coastal areas, are flaking and contour scaling (Fig. 4), granular disintegration, and surface discoloration [15]. The first two morphologies may be due to several combined phenomena, namely the mechanical effects of chiselling in shaping the column, the effects of thermal changes on the two mineralogi-cally heterogeneous rocks, and the effects of salt crystallization (mainly sodium chloride in coastal areas and gypsum in urban environments) [14, 16]. The first effect is connected to the need to sculpt granites which are very hard rocks, by keeping the chisel at roughly 90° to the surface, thus introducing a large amount of meso- and micro-cracks to a thickness of about 1–2 cm, which are not completely eliminated with the subse-quent smoothing and polishing of the columns. This results in a ‘fatigued’, more porous external layer that tends to behave differently from the substrate, and in the long run, to detach and flake off. Thermal changes occurring as a result of daily exposure to the sun and the cooling at night, cause differential expansion of the various component minerals of the two grani-toids, with consequent internal stress that favour de-cohesion phenomena and micro-fissuring (Fig. 5). In marine environments a powerful factor of decay is the presence of soluble salts which, with their well known cyclic phenomenon of crystallization and dissolution, considerably enhances the two deterioration effects described above. Discoloration may appear as the formation of a brown patina on the surface of the stone (for example on the Column of Mark in the St Mark’s Piazzetta in Venice), and should be interpreted as the effect of an initial chemical, hydro-lithic attack of the mafic components of these two stones, biotite and hornblende, from which some iron is leached out and then oxidized and hydrated at the very surface of the stone thereby forming the brown patina

In general it has been observed that the Troadic granite dete-riorates more noticeably than the Mysian granite (this observa-tion may be made on single monuments, such as the Roman Villa del Casale at Piazza Armerina (Sicily), and/or in coastal

Fig. 3 Photomicrographs of thin sections (crossed polars, all at 20X; except b and f, at 10×) of the same stone types as Fig. 1, in the same order, showing: a) euhedral granular fabric with K-feldspar, plagioclase, hornblende and quartz. b) as for a), but also with biotite in the centre. c) homeoblastic fabric formed by calcite a few quartz and plagioclase crystals. d) microbrecciated fabric with microsparitic clasts and a chlorite-containing cement. e) micritic clasts with peloids in a microsparitic cement. f ) section and internal structure of a rudist (occhio).

Fig. 4 Strong contour scaling and flaking in a column of granito misio at Murano (Venice) (left), and very heavy scaling and de-cohesion on a small column of granito violetto in the fortress of Monastir, Tuisia (right).

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towns such as Venice, and archaeological areas, such as Leptis Magna in Libya.

The crucial difference between these two granitoids resides is their grain size, averaging 8.5 mm for granito violetto, and 3.3 mm for granito misio. Their porosimetric features also differ: the average open porosity (measured with mercury-intrusion) being almost double for the former (2.18%) against 1.4% for the latter, and most probably connected to protoclastic phenomena, for example, to syngenetic fracturing that took place in the rock

during the cooling of the magma inside the Earth’s crust. The pore size distribution is also quite different, with a bimodal trend for Troadense (Fig. 6), and only very fine pores (all below 0.1 mm) for the Mysian granite.

The two breccias, the africano and breccia corallina also behave in the same way, the similar texture and fabric and overall calcitic composition and high compactness being more important than the small compositional differences. The macromorpholo-gies that have been observed in the environments considered

Fig. 5 Photomicrographs showing micromorphologies of deterioration of the two granitoids: a) showing inter-and intra-crystalline microcracks in a thin section of the troadense column of St Mark’s Piazzetta, Venice (crossed polars, 10×). b) microflaking in a hornblende crystal of the same sample (SEM).

Fig. 6 Distribution of the pore radius for marmor troadense (left) and marmor mysium (right) measured by Hg-intrusion.

Fig. 7 a) strong differential alteration along the clasts of a column of breccia corallina at Leptis Magna. b) heavy decay with loss of clasts in the africano of the base of the statue of L. Fundanius in the Forum of Paestum (Campania, Italy).

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above, show discoloration, de-cementation and powdering. The first is due to superficial dissolution of calcite produced by rain water, and re-precipitation of the same mineral as very thin white patinas: this changes the chromatic appearance of the stone, sometimes substantially. The second phenomenon is more serious since it produces incisions along the clasts (Fig. 7a), or even cavities, that may result in the loss of clasts and/or matrix (smaller clasts) of the breccias (Fig. 7b). This may be due to the strong washing effect of rain water, or more commonly, to the

effects of crystallization of soluble salts, while the third morphol-ogy is normally an intermediate step of the decaying process.

In the few haematite-marble (marmor iassense) artefacts exposed to the elements known to the present writer (for exam-ple, columns at Leptis Magna, the courtyard of the Omayad Mosque of Damascus, on the Omar Mosque, on a platform inside the Haram el Sharif of Jerusalem, and the facing slabs of the Treasury of St Mark’s Basilica in Venice (Fig. 8)), there is some discoloration of the red areas due both to the hydration of haematite and the dissolution–re-precipitation of calcite, and often more or less deep differential alteration concentrated at the interface of the greyish-white veins and the red areas (Fig. 8).

The occhio di pavone rosso (the red variety of marmor triponticum) is also rarely present in outdoor situations. In the few cases known to the author, for example, some fragments of columns and bases in the St John Basilica of Ephesus and in one column on the outside of the Archaeological Museum of ancient Neapolis (Kavala, Greece) (Fig. 8), the deterioration morphologies may be very severe including, in addition to the usual discoloration of coloured limestones (in this case from red to rose or light brown), differential decay featuring the isolation of the fossils that appear in relief with respect to the surround-ing matrix, and the de-cementation of the matrix/cement of the stone, and loss of the (often clay-like) filling of the fossil rudists (Fig. 9).

REFERENCES 1 Gnoli, R., Marmora Romana, 2nd edn, L’Elefante, Rome (1988).

2 Lazzarini, L., ‘I graniti dei monumenti italiani e i loro problemi di deterioramento’, in Materiali Lapidei II, ed. A. Bureca, M. Laurenzi Tabasso and G. Palandri, Bollettino d’Arte 41 (1987) 157–72.

3 Lazzarini, L., ‘Il granito misio, uno dei graniti più usati antica-mente’, in Marmi Antichi II: cave e tecnica di lavorazione, proven-ienza e distribuzione, ed. P. Pensabene, Studi Miscellanei 31 (1998) 111–117.

4 Lazzarini, L., ‘La diffusione e il riuso dei più importanti marmi romani delle province imperiali’, in Pietre e Marmi Antichi. Natura, caratterizzazione, origine, storia d’uso, diffusione, collezionismo, ed. L. Lazzarini, Cedam, Castenaso (2004) 101–122.

5 Lazzarini, L., Poikiloi lithoi, versiculores maculae: I marmi colorati della Grecia antica, Fabrizio Serra Editore, Pisa–Rome (2007).

6 Ponti, G., ‘Marmor Troadense; granite quarries in the Troad’, Studia Troica 5 (1995) 291–320.

7 Birkle, P. and Satir, M., ‘Geological aspects of the use of Kestanbol quartz-monzonite intrusion (Troas/Turkey) as a constructing material in archaeological sites around the Mediterranean sea’, Studia Troica 4 (1994) 144–55.

8 Lazzarini, L., ‘Des pierres pour l’éternité: les granits utilisés dans l’antiquité classique’, Les Dossiers d’Archéologie 173 (1992) 58–67.

9 De Vecchi, G., Lazzarini L., Lünel T., Mignucci, A. and Visonà, D., ‘The genesis and characterisation of “Marmor Mysium” from Kozak (Turkey), a granite used in antiquity’, Journal of Cultural Heritage 1 (2000) 145–153.

10 Andreoli, A., Berti, F., Lazzarini, L. and Pierobon Benoit, R., ‘New contributions on Marmor Iassense’, in ASMOSIA VI, Interdiscipli-nary Studies on Ancient Stone, ed. L. Lazzarini, Bottega d’Erasmo, Padua (2002) 13–18.

11 Ballance, M., ‘The origin of Africano’, in Papers of the British School at Rome 34 (1966) 79–81.

12 Lazzarini, L., ‘The origin of “Breccia Nuvolata”, “Marmor Sagarium” and “Marmor Triponticum”, in ASMOSIA V, Interdisci-plinary Studies on Ancient Stone, ed. J.J. Herrmann, N. Herz and R. Newman, Archetype, London (2002) 58–67.

13 Folk, R.L., ‘Practical petrographic classification of limestones’, American Association of Petroleum Geology Bulletin 43 (1959) 1–38.

14 Lazzarini, L. and Tabasso Laurenzi, M., Il restauro della pietra, Cedam, Padua (1986).

Fig. 9 Differential alteration and powdering in a fragmentary column of occhio di pavone rosso on the outside of the Archaeological Museum of Kavala (ancient Neapolis), Greece.

Fig. 8 Pronounced differential alteration between the white veins and red matrix in four slabs of marmor iassense facing the exterior of the ‘Treasury’ of St Mark’s Basilica in Venice.

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15 ICOMOS-ISCS, ICOMOS-International Scientific Committee for Stone Illustrated glossary on stone deterioration patterns, ICOMOS, Champigny-sur-Marne (2008).

16 Lazzarini, L., ‘General issues on the deterioration of stone’, in The Building Stone in Monuments, Proceedings of a Interdisciplinary Workshop, Athens and Mytilene, Ministry of the Aegean, Athens (2002) 149–160.

AUTHORLORENZO LAZZARINI is a geologist and Full Professor of Applied Petrography at the Università I.U.A.V.di Venezia where he directs the

LAMA (Laboratorio di Analisi dei Materiali Antichi) belonging to the Department of Architectural History. He is a Fellow of IIC and member of several national and international academic institutions. He has participated in many international conservation projects launched by UNESCO and ICCROM, and has extensively published in the field of characterization and conservation of building and decorative stones used in antiquity, in the scientific examination of paintings, and in the archaeometry of pottery. He has recently written a book on the most important coloured stone of Greek origin used in classical and post-classical times. Address: LAMA, San Polo 2468, 30125 Venezia, Italy. E-mail: lorenzo@iuav.it