Original article
Discovering the stone heritage of southern Italy: technical properties of the Mondragone marble from Campania region Roberto de Gennaro Æ Domenico Calcaterra Æ Pio Di Girolamo Alessio Langella Æ Maurizio de’ Gennaro
Abstract The results of the geological characterization of an old stone building in southern Italy, are presented here. The Mondragone marble is a slightly metamorphosed carbonate rock, which was widely employed as monumental stone in the 18th century Royal Palaces of Naples and Caserta. In this paper, for the first time, this rock has been investigated with a thorough laboratory testing program, aimed at defining its mineralogical, physical and mechanical parameters. The two most important varieties of Mondragone marble were separately tested: the yellow and grey marbles (hereafter, YM and GM, respectively). The results obtained from physical tests (open porosity, dry density, specific gravity, water absorption coefficients, ultrasonic velocity) did not show marked differences between the two materials; in contrast, the mechanical strength tests (uniaxial compressive strength, point load strength, flexural strength) showed better behaviour of YM than for GM. After a tentative comparison with other well known carbonate rocks from Italy, some considerations on the response of Mondragone
Received: 15 January 2002 / Accepted: 26 November 2002 Published online: 18 April 2003 ª Springer-Verlag 2003 R. de Gennaro (&) Æ P. Di Girolamo Æ M. de’ Gennaro Dipartimento di Scienze della Terra, Universita` degli Studi di Napoli ‘‘‘Federico II’’’, Via Mezzocannone, 8, 80134 Napoli, Italy E-mail:
[email protected] Tel.: +39-81-5473363 Fax: +39-81-5518701 D. Calcaterra Sezione di Geologia Applicata, Dipartimento di Ingegneria Geotecnica, Universita` degli Studi di Napoli ‘‘‘Federico II’’’, P.le Tecchio, 80, 80124 Napoli, Italy A. Langella Dipartimento di Studi Geologici ed Ambientali, Universita` del Sannio, Via Port’Arsa, 11, 82100 Benevento, Italy
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marble to local weathering were conducted. In particular, the weathering typologies were related to the particular texture of the brecciated marble and the different strength resistances displayed by the various constituents of the rock. Keywords Campania region Æ Italy Æ Laboratory tests Æ Mondragone marble Æ Physico-mechanical properties Æ Weathering
Introduction The Mediterranean area holds the largest and most important historical, artistic and archaeological heritage of the world, a great part of which is made of valuable building stones: these materials were quarried and traded throughout the Mediterranean basin by the major civilizations of the past, such as the Egyptians, Greeks and Romans. With the fall of the Roman Empire, the use of locally available stones became more and more significant until the Industrial Revolution, although some remarkable exceptions have to be cited, such as the Carrara marbles. Building stones from southern Italy and their usage have followed a similar path over the past centuries. A meaningful example of these local stones is given by the city of Naples, for several centuries the capitol of the Reign of Naples and of the Two Sicilies. In the Angevin period (13th–15th century), the Neapolitan Yellow Tuff became a distinguishing stone used in monumental buildings (S. Chiara and S. Domenico churches, Maschio Angioino and Castel dell’Ovo). Another volcanic material, Piperno from the Phlegrean Fields, assumed a paramount role in the architecture of the city from the 13th to the 19th century. A strong impulse to use stone from all the southern Italian regions occurred during the Bourbon period (18th and 19th century). Beside volcanic rocks, several sedimentary lithotypes were used, most of them derived from Sicily region, but also from the Caserta, Benevento and Avellino provinces in the Campania region. This situation lasted until the second half of the 19th
DOI 10.1007/s00254-002-0751-4
Original article
Fig. 1 Geological sketch map of Mt Massico (SW sector; Cestari 1965). Numbers refer to the main outcrops of Mondragone marbles, corresponding to the quarries cited in the text (1 S. Sebastiano, grey marble; 2 Masseria Molara, grey marble; 3 Canal Grande, grey marble; 4 Canal Grande, Cipoline marble; 5 S. Mauro, yellow marble)
century when, due to improvements in transportation facilities and a new political context (proclamation of the Reign of Italy in 1861), local stones were progressively replaced by more valuable materials that came from central and northern Italy or even abroad. As a consequence, even good quality local stones were no longer employed and they progressively suffered a loss in interest. Nowadays, the conservation of cultural heritage is a major duty for all countries, and it has been realised that very little is known about several of these local materials, which have marked entire architectural epochs. In southern Italy, a systematic study of the local building stones has only recently begun. As far as the Campania region is concerned, the contribution of volcanic tuffs used as dimension stones has already been reported (de’ Gennaro et al. 1995; Calcaterra et al. 2000), whereas less attention has been paid to other rocks of local interest, such as the sedimentary rocks. This paper represents another step in the rediscovery of the stone heritage of Campania. In this framework, the Mondragone marble holds a top rank position because it was the most repre-
sentative building stone under the Bourbon kings, who used it in all their royal palaces. Furthermore, this research integrates the work already started by Di Girolamo et al. (2000) and allows us to obtain a detailed knowledge of the Mondragone marble from a mineralogical–chemical and a physico-mechanical point of view. Apart from scientific interest, the information reported here can be advantageously used by whoever needs to operate in the field of safeguarding and restoring monuments.
Materials The so-called Mondragone marble outcrops at Mt Massico, a small NNE–SSW-trending carbonate monocline, located in the north-western portion of the Campania region (Fig. 1). The marbles are included in two flysch-like sequences of Tertiary age, tectonically overlying the Mesozoic to Tertiary carbonate bedrock of Mt Massico
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Fig. 3 Polarizing micrographs of GM (a plane polars) and YM (b crossed polars)
Fig. 2 Mondragone marble slabs: A brecciated yellow variety; B brecciated grey variety; C Cipoline variety
(Di Girolamo et al. 2000). The Mondragone marble consists of two main lithofacies: the Brecciated marble and the Cipoline (i.e. banded) marble. The Brecciated marble can be further subdivided in two types known as the yellow (YM) and black (GM) marbles (Penta 1935), the latter was defined as grey because of its real, prevailing colour (Fig. 2). All these rocks were quarried until several decades ago in the southern and northern sectors of Mt Massico. YM was quarried from just one site (S. Mauro, outcrop 5 in Fig. 1), whereas GM came from at least three different places (Canal Grande, outcrop 2; Masseria Molara, outcrop 3; and S. Sebastiano, outcrop 1; see Fig. 1). Furthermore, in the Canal Grande quarry there is also another variety of marble present, known as Cipoline marble (outcrop 4, Fig. 1), which shows a minor extension when compared with other lithotypes. The main minero-petrographic properties of the formation have already been described in detail by Di Girolamo et al. (2000); however, some noteworthy features will be 268
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described here. Cipoline marble consists of alternating bands, coloured from light to dark grey, brown, yellow or black, and has a texture that ranges from xenoblastic to granoblastic-polygonal. The mortar texture and calcite wavy extinction are often observed in a single band; the plastic deformation produces a boudinage. The darkest bands contain graphitic matter, whereas the yellow bands are richer in dolomite. Cipoline marble is also characterized by diopside to salite clinopyroxene, whose chemical composition is similar to that of marbles produced by medium to medium-high grade amphibolite facies metamorphism, which occurs in the Eastern and Central Alps (Tromsdorff 1966). Both the Brecciated varieties (Fig. 2) can be defined as polygenic sedimentary breccias (Di Girolamo et al. 2000), with dark to light grey lithoclasts of variable origin and dimension (up to 10 cm in YM), which are bonded by a carbonate cement, along with minor amounts of biotite and illite. YM is characterized by a deep, yellow matrix, whose colour is essentially due to limonite and a small content of dolomite cement. The darker colour of the GM is a consequence of a prevailing, if variable, occurrence of carbonaceous matter. Both marbles show a micritic matrix (Fig. 3a) with widespread irregular spatic veins of diagenetic origin. Crystal grain size in spatic veins ranges between 0.1 and 0.5 mm whereas crystals of the
Original article
micritic matrix never exceed 5 lm in diameter. In contrast, YM sometimes shows metamorphic features such as a xenoblastic to granoblastic texture (Fig. 3b). As well as calcite, small amounts of dolomite, quartz, biotite and montmorillonite have also been recorded. The occurrence of traces of talc and tremolite is a result of the low grade metamorphism in carbonate rock. The yellow matrix includes minute fragments of volcanics (pumice, scoriae and devitrified rhyolitic obsidians), plutonics (granites and granodiorites), metamorphics (gneisses and quartzites), sedimentary rocks (sandstones) and scattered mineral fragments from the above rocks, such as green hornblende, quartz, andesine–labradoritic plagioclase, biotite and cordierite (Di Girolamo et al. 2000).
