a Dipartimento di Scienze della Terra, Universita Federico II, Via Mezzocannone 8, Naples, Italyb Dipartimento d’Ingegneria Geotecnica, Universita Federico II, Piazzale V. Tecchio 80, Naples, Italy
c Facolta di Scienze, Universita del Sannio, via Port’Arsa, 11, Benevento, Italy
Keywords: building stone / cultural heritage / Naples / Italy / thematic maps / weathering
1. Introduction
Archaeologists and town planners have oftenhighlighted the close relationship between urbansettlements and their geological and geomorphologi-cal context, stressing in particular their buildingstones, which represent their essential backbone.
Southern Italy has several cities which bear wit-ness to this symbiosis between architecture and geol-ogy: for example, Agrigento, Siracusa, Matera andLecce have always been considered ‘Cities of stone’.
Naples must be included in this list, since it hassuch a close relationship with its building stonesthat the concept of ‘architectural cultivation of theland’ may be used to describe it. The city stillcontains evidence of the sites where its main build-
ing materials were quarried over the centuries: TufoGiallo Napoletano (Neapolitan Yellow Tuff, here-after NYT), Piperno sensu strictu (hereafter, s.s.)and pozzolana. Many of the city’s best examples ofarchitectural harmony owe their beauty to the par-ticular yellowish-grey stone of which they are built.
All these features, combined with the urbanisticsetting of the city, which has preserved over theyears the arrangement of the original Greek‘Neapolis’, make it a unique case among those an-cient cities which have always interested historiansand art experts (as demonstrated by the abundantliterature on the subject, to which readers are re-ferred for all detailed aspects which go beyond thescope of the present research and specificcompetences).
Many studies have been carried out on the stoneof which most of the main architectural works ofNaples are built. However, these extremely detailedresearches have mainly been performed from the
* Correspondence and reprints:E-mail address: [email protected] (M. de’ Gennaro).
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viewpoints of architecture or art history [1]. Thosedealing with the basic building materials from amore closely mineralogical, petrographical and engi-neering-geological viewpoints, for better identifica-tion of the decay processes to which they are sovulnerable, are quite rare [2, 3].
The double aim of this research is to provide anear complete scheme of the building stone used‘facciavista’ in the historical architecture of Naples,supplying operators in the sector with a basic tool toface problems connected with the preservation andrecovery of monuments. The detailed research onbuilding stone in this area was started within theframework of the ‘Cultural Heritage’ project of theItalian National Council for Research. The firstphase of this research, consisting of a detailed sur-vey of the materials and an evaluation of their stateof deterioration, led to the preparation of two the-matic maps and a database, the contents of whichare illustrated and discussed here. The results also
allow the second part of the research to be planned.Its main aim is to extend knowledge on the be-haviour of some characteristic lithotypes, such asPiperno s.s. and NYT, both as regards interactionswith the micro-environment characterizing the vari-ous areas and, where possible, identification of theprovenance of these lithotypes.
2. Methods
2.1. Boundaries of study area
The study area, covering about 1.5 km2, predomi-nantly coincides with the original urban settlementof ‘Neapolis’, dating back to the 5th century B.C., inwhich the old plan of the road grid can still today berecognized, occupying three main streets (the ancientdecumani ) running E-W and some dozens of alley-ways (cardini ) at right angles to them. The studyarea is bounded to the north by Via Foria, west byVia Monteoliveto and Via Pessina, and south byCorso Umberto I; it extends east beyond ViaDuomo, to include Via Rosaroll (figure 1).
2.2. Cartographic processing of data
This study was planned using a digital map, scale1:1000, used to prepare two thematic maps: one ofmaterials and lithotypes, and one showing weather-ing. The data were composed in digital format, incollaboration with the company Nadir of Pozzuoli(Naples), which used the Autocad software byAutodesk. The cartographic material presented herefollows the first Italian experience in this field, com-pleted in 1992 by the working group of the Univer-sity of Siena [4]. The survey was carried out mainlyon the perimetral facades of each building or block.Since main public buildings contain many architec-turally splendid cloisters and courtyards, most ofthem have been surveyed as well [5].
Data collection, and in particular the descriptionof weathering typologies were made according tothe NORMAL 1/88 recommendations [6].
Surveyed materials were mapped in seven units,using lines of different colours (plate 1 – see sepa-rate map supplied with this issue). Most of theidentified building stones were classified using agenetic criterion (igneous, metamorphic and sedi-mentary rocks) whereas local volcaniclastic stones,which represent the prevailing materials, whereclassified in two distinct categories: the NYT andPiperno sensu lato (hereafter, s.l.). The latter classconsists of either the Piperno s.s. or some varieties
Figure 1. Boundaries of the study area within the ancientcity centre of Naples.
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Figure 2. Database: building frontsheet.
2.3. CentrAntico database
The building material related database, CentrAn-tico, was developed with Borland Delphi 2.0 soft-ware. The individual building reports were enteredin the database, with an identificative numericalcode, a short description of the building, the ex-posed area, and its toponymical ubication (figure 2).The report of the materials utilized for the building,with the relative quantities, were also provided.Furthermore, the semi-quantitative evaluation of theweathering, and, whenever possible, a short descrip-tion of the decay phenomenologies, according to theNORMAL 1/88 recommendation [6], were indi-cated (figure 3). As regards the surveyed surfaces,those belonging to facades were separated fromthose relating to architectural parts, not consideringthe latter in the overall building surfaces.
The file-cards of the more relevant buildings(churches, abbeys, basilicae, etc.) also include fur-ther information, such as the specific materials inset,a detailed view of the facades and additional photos.
The database structure is ‘open’, allowing it toalso be implemented in different urban environ-ments and with any kind of lithologies: in fact, thedatabase automatically updates.
The provided queries were performed in order toallow the cross-search of materials and weatheringgrades; moreover, it is also possible to carry out the‘and/or’ query (figure 4). The search results showdifferent weathering features for the specific mate-rial. Successively, the database was linked to thethematic maps, described above, making it similar toa GIS-like system.
3. Results
In the ancient city centre of Naples a total ofabout 1 100 000 m2 of exposed surfaces was sur-veyed, slightly more than 10 % being composed offace brick stone ( facciavista) (figure 5). Followingpreliminary steps of the research project [8], theresults obtained on each lithotype are describedbelow.
3.1. Piperno s.s. and Piperno-like materials
Piperno s.s. is the best-known magmatic rock inthe Neapolitan area, despite the fact that it cropsout to a very limited extent with respect to the otherpopular building stones, such as the NYT. Pipernos.s. in fact only crops out east of the Campi Flegreiarea, i.e., on the flank of the Camaldoli hills, at
of the grey facies of Campanian Ignimbrite, theso-called ‘piperno’, tufo pipernoide (pipernoid tuff),tufo grigio (grey tuff) [7]. The materials making upcontinuous surfaces are also reported with continu-ous lines. Dashed lines indicate architectural partscomposing string-courses, pilaster strips, cornices,corbels, sills and steps. In view of their extent, it wasproposed to use a single specific symbol for severalarchitectural elements such as portals, corner-stonesand columns. On the maps, the parallel continuouslines from the exterior to the interior represent thesequences of different lithotypes which compose thesame facade (from bottom to top).
Weathering was surveyed and mapped accordingto three grades of intensity: high, moderate andnegligible (plate 2 – see separate map supplied withthis issue). The extent of specific alteration wasmeasured in a semi-quantitative way for each mate-rial, in relation to the total surface area exposed.Evaluation of the extent of weathering does not takeinto account the age of emplacement of the materi-als and therefore of possible recent replacements.Each grade of weathering is given a different colour,irrespective of type of material.
Surveyed data are expressed in terms of surfacearea exposed, by means of an estimate of the eleva-tion of single buildings. The whole was thenclassified into a list of about 1500 records, whichrepresent the basis of the database prepared by theNadir company according to a scheme developed bythe research staff.
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Figure 3. Database: materials frontsheet.
Pianura and Soccavo (e.g., Verdolino, TorreFranco). It ranges in thickness between a few metresand a few dozen metres, and it is covered by apyroclastic succession, some hundred metres thick,conditioning the quarrying techniques. As regardsits genesis, some authors believe that this volcanicproduct is a proximal facies of the CampanianIgnimbrite (37 000 yr B.P.) [9]. Other authors hy-pothesize a local volcanic episode of younger ageanalogously to other Phlegrean breccias [10, 11].
This eutaxitic rock is composed of centimetre- todecimetre-sized collapsed scoriae ( fiamme) set in ahard grey matrix related to vapour phase devitrifica-tion. The fiamme have a length sometimes greaterthan 50 cm and an average flattening ratio of 1:10.Phenocrysts of alkali feldspar (Or68–43) and subordi-nate plagioclase (An86–28), clinopyroxene [Mg/(Mg+Fe++)=85–47] with minor amounts ofamphibole and sodalite are set in a totally recrystal-lized matrix, in which alkali feldspar (Or53–34) is themain phase. The fiamme volcanic glass was partiallyreplaced by tiny new formed crystals of alkalifeldspar showing the same composition as those ofthe matrix (figure 6).
The fiamme have a trachytic composition (SiO2
range: 60.9–63.5 wt%; K2O: 6.8–7.3 wt%, – ox-ides expressed on dry basis) and in some cases showperalkaline affinity (Agpaitic index= [(Na2O+K2O)/Al2O3], on molecular basis, up to 1.14).
Moreover, minor elements are extremely high (e.g.,Nb up to 121 ppm).
Although widely employed for over 300 years,Piperno s.s. has been poorly studied from the engi-neering-geological standpoint: the very few dataavailable from literature date back to 1820 and1869 [12]. Only recently a systematic research onPiperno s.s. has been undertaken. The first data [13,14] give dry density between 15.7 and 18.6 kN/m3,
Figure 4. Database: search frontsheet.
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Figure 5. Pie-chart showing distribution of building mate-rials (a) and building stones (b).
clase, alkaly feldspar and biotite are recognized.From a chemical point of view, products of Campa-nian Ignimbrite range from trachyte to trachyphono-lite.
The increasing eutaxitic texture towards the bot-tom of the deposit, along with an increase in boththe bulk density and compressive strength deter-mines a gradual passage from an almost incoherentfacies (locally known as cinerazzo) to a Piperno-likerock texture. In the lower layers (piperno and Piper-noid tuff, subordinately), an alkali-feldspar occurs(vapour phase crystallization) as transformationproduct of the glassy fraction [7].
This stratigraphic variation is well evident in thequarries located in the northern sector of theCaserta province (Puccianello locality) where thetuff shows a gradual passage to piperno, from thetop to the bottom. The consistency of the tuffincreases and the scoriae, chaotically distributed inthe upper part, assume a clear iso-orientation as aconsequence of the collapse. From the macroscopicfeatures of the piperno are obtained: reasonablyhigh strength, a dark grey colour and, above all, theeutaxitic texture, even though the scoriae ( fiamme)
Figure 6. Micrographs of Piperno s.s. (×40): a) planepolarized light; b) crossed polars.
porosity ranging from about 15 to 50 %, and uniax-ial compressive strength variable over a wide range(15–60 MPa).
As well as Piperno s.s., other Piperno-like materi-als have been used in Neapolitan architecture, likelycoming from the Campanian Ignimbrite Formation.
The Campanian Ignimbrite represents the volcanicproducts of a huge eruption (37 000 yr B.P.) [15,16] which covered a large part of the Campanianregion over an area of about 30 000 km2 [17] and itis recorded also in the eastern Mediterranean area(e.g. layer Y5 of Keller et al. [18]).
Source location for the Campanian Ignimbrite isstill controversial. Many authors [17, 19] suggestedan origin in the Campi Flegrei area, other authorsproposed that the eruption took place north ofCampi Flegrei along a fracture zone [20], or in theCampanian Plain [21].
A typical section of Campanian Ignimbrite com-prises a fall deposit overlayed by an ignimbrite. Theignimbrite s.s. is a grey or sometimes yellow tuffwith grey or yellow pumices or scoriae set in matrixof the same colour. Moreover, lithics and crystalsare recognizable. In thin section pumice fragments,shards, salitic and diopsidic clinopyroxene, plagio-
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Figure 7. Different cut of Piperno s.s. stone: verso (a);contro (b).
kN/m3 while the porosity is always very high, rang-ing between 50.4 and 58.6 %.
Among the building stones used in the city ofNaples, the assemblage Piperno s.s. and CampanianIgnimbrite is the most widespread: these materialscover more than 57 000 m2 and represent more than50 % of the total (figure 5b).
The occurrence of ellipsoidal fiamme, particularlyfor Piperno s.s., identifies in the stone a direction(verso) of lower mechanical resistance (16 MPa[13]) parallel to the major axes of the fiamme them-selves (figure 7a). The perpendicular direction (con-tro, figure 7b) seems to have higher mechanicalresistance (38–40 MPa [13]).
The pattern of the stone owes its peculiarity to thedark grey-blackish fiamme themselves, immersed ina light grey matrix. These features probably led tothe choice of the cutting direction of the dimensionstones employed as structural elements (e.g. col-umns), which always bear the load in the controdirection. The facing slabs were mostly sawn follow-ing the contro direction, so as to get the best aes-thetic effect; nevertheless, in many cases slabs cut inboth other directions have been observed, i.e. theverso and the secondo directions.
It was probably for this reason that Piperno s.s.was widely used in the buildings of the ancient citycentre, predominantly for partial or total facings,reaching its maximum expression in the PontanoChapel, the Palazzo Cuomo (now the FilangieriCivic Museum), and in the rustication of the facadeof the Gesu Nuovo Church (formerly Palazzo San-severino), all built around the end of the 15thcentury (figure 8). Piperno s.s. was also extensivelyused as a load-bearing structural element, especiallyfor the colonnades of the cloisters of the manyconvents and monasteries in the area (figure 9).
As regards the distribution of Piperno s.s. and itsrelated facies, the map (plate 1 – separate mapsupplied with this issue) clearly shows that it ismainly concentrated in the ‘epicentral’ part of thearea, which is also that containing the oldest build-ings. In the more peripheral sectors, partly as aconsequence of urban restorations during the secondhalf of the 19th century, Piperno-like materials arereplaced by other lithotypes, such as lavas.
As far as Campanian Ignimbrite is concerned itshould be remarked that this material has been used,to some extent, as a replacement stone for Pipernos.s. mainly for the accomplishment of less exposedand less visible architectural parts. Several reasonsfavoured the introduction of this material startingfrom the end of the 18th century, such as a similaraspect, its easier workability, lower costs and, above
are, on average, smaller than those of Piperno s.s.The intermediate layers show transitional features,especially when scoriae are concerned, being lessiso-oriented and collapsed. This material is com-monly called ‘pipernoid tuff’.
Mineralogical composition of Campanian Ign-imbrite is very similar to the Piperno s.s.; K-feldsparand plagioclase are major phases, their sum reachingup to 90 % wt. Always subordinate are clinopyrox-ene, biotite, hematite and sometimes calcite.
No differences are reported among matrix andscoriae, from the chemical point of view: both canbe considered as trachyte (SiO2 range: 61.5–59.3;K2O 7.2–6.6). As regards physical–mechanical fea-tures, dry density range is between 22.3 and 25.9
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all, the growing demand for building stone follow-ing the city’s expansion and the increasingly loweravailability of Piperno s.s, mainly because of grow-ing quarrying difficulties and consequently higher
Figure 9. Colonnade in S. Andrea delle Dame cloister.
Figure 8. Some relevant monuments made with Pipernos.s. (a) Pontano Chapel; (b) Filangieri Museum; (c) GesuNuovo Church.
costs. The possible source area of this Piperno-likematerial (Campanian Ignimbrite) could be localizedboth in the Salerno province (Nocerino-Sarnesecampagna) and the Caserta province (Puccianello,Pozzo Vetere, etc.).
As may be deduced from the brief geological noteat the beginning of this section, the only possibilityof obtaining Piperno s.s. was by underground quar-rying, which was laborious and also dangerous. Thechronicles of the times report a tragic accidentwhich occurred in October 1739, in which elevenPiperno quarrymen died [1]. At the end of the 18thcentury, Pianura and Soccavo were probably con-nected by a network of tunnels on several levels.Today, these underground quarries are almost en-tirely forgotten, thus disregarding sites so importantfor the history and culture of Naples.
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However, even though strange to relate, Pipernos.s. has been sporadically used as facing or as anarchitectural part in recent buildings, obviously out-
side the boundaries of the ancient city. Officialreports testify that in 1931 about 130 tons ofPiperno s.s. were still extracted [1].
In spite of the good physical and mechanicalproperties of Piperno s.s. and related facies, it issubject to intense and extensive processes of decay.About 95 % of the exposed surfaces were affectedby moderate to high weathering grade (figure 10),mainly due to stains or artificial patinae, fissuring,alveolization, sometimes disaggregation and surfacedeposits of organic origin (figure 11).
3.2. Neapolitan Yellow Tuff
This is the most abundant volcanic product in theNeapolitan urban area. It owes its fame to thelithified facies that has been used as a buildingmaterial since ancient times because of its colour,light weight, and good insulating properties; at thesame time it is weak enough to be easily sawn intodimension stones.
The lithified NYT outcrops within the city ofNaples and along the topographic border of theCampi Flegrei (Monte di Procida, Cuma, Monte S.Severino, Quarto and the hill of Camaldoli). Thispyroclastic deposit is made up of pumice, obsidianfragments, crystals and lithics set in an altered ashymatrix containing zeolites and subordinate clay min-erals. Its composition ranges from trachyte and al-kali-trachyite to phonolite. The few phenocrysts ofNYT are represented by alkali feldspar, salitic anddiopsidic clinopyroxene, biotite, plagioclase andmagnetite [22–24].
NYT has been the most frequently used buildingstone in and around Naples ever since remote his-torical times (4500 yr B.P. – [25, 26]). Although itcrops out extensively, underground quarries werefor centuries preferred to open-pit ones, very proba-bly in order to save the ground for other anthropicactivities. The legend of the Cimmerii people isperhaps linked to this ancient practice: the Cimmeriiwere in fact people supposed to live in caves con-nected to each other by tunnels, composing a trueunderground city [27].
Most of the walls of the buildings in the citycentre are composed of NYT which, before theadvent of reinforced concrete, performed not onlyarchitectural but mainly structural functions, thankspartly to its good physical and mechanicalproperties.
NYT can be defined as a weak rock, which hasbeen thoroughly studied in the last decades [28–30].It is characterized by low values of several parame-ters, such as bulk density (10.3–13.7 kN/m3), uni-
Figure 11. Weathering typology (alveolization) of Pipernos.s.
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Figure 12. Some monuments made with ‘facciavista’ NYT. (a) S. Giovanni a Pappacoda Chapel; (b) S. DomenicoMaggiore; (c) S. Chiara; (d) Academy of Fine Arts.
axial compressive strength (0.3–10.7 MPa) and ul-trasonic P-waves (1500–2000 m/s); on the otherhand, NYT shows a quite high porosity, rangingbetween 40 and more than 60 %.
However, there were also other factors whichpromoted the use of NYT for building purposes,i.e., its mineralogical composition and textural fea-tures. It is the high porosity, along with the abun-dant presence of zeolites (mainly phillipsite andsubordinate chabazite) in the bonding matrix, thatmakes this rock a good heat and sound insulator.
In most cases, tuff blocks were coated by plasterwhich, when applied with traditional techniques,definitely protected them from physical and chemi-cal attack by atmospheric agents. Frequently, inthe case of monumental buildings, the tuff wasused facciavista.
NYT is mainly found in important monumentsusually going back to Angevin times (figure 12),such as the 13th century S. Giovanni a PappacodaChapel, the Basilicas of S. Domenico Maggiore, S.Chiara, S. Lorenzo Maggiore and S. Pietro a Ma-
jella and other more recent ones such as the Ac-cademia di Belle Arti (Academy of Fine Arts), builtin neo-Renaissance style in 1864 by Enrico Alvino,who transformed the former convent of S. Gio-vanni delle Monache (figure 12d). The NYT em-ployed in the most noticeable monuments alonereaches up to about 50 % of the total (46.4 %).
Unexpectedly, the exposed and unprotected sur-faces of NYT make up only about 17 % ofthe total materials surveyed (figure 5). The stateof preservation of NYT is generally better thanthat of Piperno s.s. (figure 13). About 50 % ofthe surfaces show only slight weathering, althoughthe physical and mechanical characteristics of thetuff are worse than those of Piperno s.l., lavas,marbles, etc.. As regards this aspect of the prob-lem, an essential role is certainly played by the factthat the tuff was used for building continuousfacades and facings of relevant extent. It shouldalso be noticed that NYT was and still is easilyreplaceable, as certainly proved in some cases (seebelow).
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Figure 13. Pie-chart showing weathering grades of NYT.
elements, until then mostly realized with Piperno s.s.In fact, as already stated, quarrying this rock be-came more and more difficult since the 18th cen-tury, inducing the quarrymen to find validsubstitutes for the Piperno s.s., which had domi-nated for about three centuries the local buildingscene.
Lava flows belonging to the Somma-Vesuviuscomplex, and, subordinately, to the Campi Flegreivolcanic district were recognized.
The Somma-Vesuvius lavas are petrographicallytephrite to phonolitic tephrite and have porphyritictextures, with clinopyroxene and plagioclase phe-nocrysts. Leucite and alkali feldspars are present inthe groundmass.
The Campi Flegrei lavas are trachytic in composi-tion and show a typical porphyritic structure withsanidine as peculiar phenocryst phase; clinopyrox-ene and plagioclase are subordinate as phenocrysts.In some cases biotite, amphibole and feldspathoid(sodalite) can be recognized. The possible sourceareas are Cuma, Punta Marmolite and Pozzuoli(Monte Olibano), as the Campi Flegrei lava flowsare very subordinate with respect to the pyroclasticproducts (pumice, tuffs, ignimbrites, scoriæ and soon).
Plate 1 (see separate map provided with this issue)clearly shows that lavas are mainly found in theperipheral parts of the city and particularly in theareas involved in restoration works carried out aftera cholera epidemic (1884), and lasted until thebeginning of the 20th century. This amount of lavassums up to about 15 % of the total.
Most of the buildings on Corso Umberto (themost important street of the southern area, inaugu-rated in 1888) have lava basal facings, like thosemaking up the block between Via P. Colletta andthe lower part of Via Duomo (figure 14). Thenorthern boundary of this sector follows an E–Wtrend: Via del Sedile di Porto, S. Marcellino, ViaCapasso, and Via Arte della Lana. There are, how-ever, some examples of lava used in more remotetimes such as the colonnade of the cloister (figure15), tiled in majolica, of the Convento di S. Chiara[31].
Like Piperno s.l., lavas may be extensively weath-ered, in spite of their very good physico–mechanicalproperties (figure 16). More than 47 % of the sur-faces show a high degree of weathering, and about15 % of surfaces a moderate one. The most wide-spread phenomena are scaling and exfoliation andsometimes large-scale lacking (figure 17).
Other igneous rocks were far less often used thanlava in the historical architecture of the ancient city
The most frequent weathering typologies of NYT[3, 8] are:� alveolization: mainly due to detachment of lithic
clasts or disgregation of zeolitized pumices;� scaling and exfoliation: both due to the action of
damp waters through the stone and later recrys-tallization of soluble salts;
� disaggregation: also due to infiltration of waterand the consequent dissolution of the constituentphases of the stone (crystalline and/or amor-phous);
� patinæ, stains, efflorescences: extensively presenton surfaces subjected to intense dissolution andevaporation of damp waters.As it can be easily argued from this list, the main
factor causing weathering of the tuff is clearly mois-ture, due to rising damp as well as rainfall. Theprocess is always worst at the zones along whichevaporation due to rising damp is highest. The greatheterogeneity of the rock means that decay alsospreads in an irregular way, so that it occurs to verydifferent extents even in adjacent blocks of stone.
Unlike the case of Piperno s.s., it is very difficultto define the provenance of the tuff used for thesebuildings, both because it often came from the sub-soil of the area on which the monument now risesand because, as already reported, during partialrestoration works, materials coming from othersources were very probably used instead of theoriginal ones. This is certainly the case of the post-war restoration of the Basilica di S. Chiara, whosefacades were reconstructed partly using blocks takenfrom quarries active at that time on the flanks ofCamaldoli between Chiaiano and Marano.
3.3. Lavas and other igneous rocks
Lava was extensively used both for paving roadsand, to a lesser extent, at least until the second halfof the 19th century, for architectural or structural
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Figure 14. Example of ‘recent’ employment (19th cen-tury) of lavas.
Figure 16. Pie-chart showing weathering grades of lavas.
Figure 17. Detail of a S. Chiara cloister lava column. Inevidence spalling and exfoliation.Figure 15. Colonnade of S. Chiara cloister.
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Figure 18. Granite column.
3.4. Marbles
Some staircases, and in particular many portalsexecuted to a high level of artistic quality, are inCarrara marbles, e.g., those of the S. Giovanni aPappacoda Chapel (figure 19a) and of the Cathedral(figure 19b), by Baboccio da Piperno. These finelyworked architectural features, with their many stat-ues, have been badly attacked by physical and chem-ical agents, and have not even been spared byvandals. Almost 85 % of the exposed surfaces showmoderate and high degrees of weathering. Protru-sions, sharp corners, and intarsio features have suf-fered the worst damage, and were eroded byabrasion and corrosion. The chemical action of themicro-environment has often caused surface disag-gregation, due to sulphatation of calcite.
3.5. Sedimentary rocks
Sedimentary rocks compose slightly more than8 % of the total amount of building stones in theancient city centre of Naples.
Limestone is the most abundant (:5 %). It wasused in slabs on the facade of the Cathedral (13thcentury, restored in the second half of the 19thcentury), or sometimes as dimension stones withboth structural and ornamental functions in thebelltower of the Basilica of S. Chiara. It presumablycame from the carbonatic ridges of the nearbyprovinces of Caserta and Benevento. A preliminarymicropaleontological analysis has shown that thelimestone of the S. Chiara belltower came from theMiocenic formation of Cusano (figure 20), large
Figure 19. Marble portals of S. Giovanni a Pappacoda (a)and of Cathedral (b).
centre. The granitoid rocks of the Neapolitanarchitecture come from areas outside Campania re-gion. They show a composition ranging from gran-odiorite to granite with a colour varying from greyto red, testifying different sites of provenance. Themost likely localities could be Sardinia and/orEgypt.
These rocks were only used for architectural fea-tures such as columns and friezes (figure 18), oftenincluding materials coming from pre-existing Greekand Roman buildings.
Overall, these materials only represent less than1 % of all those used. The intensity of weathering isgenerally moderate, even though lacking, exfolia-tion, stains and patinæ, the latter mainly due toatmospheric pollution, are sometimes observed.
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Figure 20. S. Chiara belltower (a) and plane polarizedlight micrograph of Cusano limestone (b, ×40).
These materials have undergone a severe decay, aswell. The most frequent phenomena are fissuring,the complete lacking of more or less large portions,superficial micro-cracking, exfoliation, patinæ orstains due to chemical attack by meteoric agents,but also to encrusted dust and sometimes evenvandalism.
3.6. Bricks
Definitely subordinate to all the other materials isbrick which, in urban and geological contexts verydifferent from that of Naples, may play a muchmore significant role [4].
The Medieval belltower of Pietrasanta (figure 21)is almost entirely made of bricks. Bricks were alsoused for a part of the southern facade of the Basilicaof S. Domenico Maggiore and the uncovered wallsof some patrician palaces (Casacalenda, Firrao).
Figure 21. Pietrasanta belltower.
outcrops of which are located, among others, at theAurunci, Matese and Tifatini Massifs.
Travertine was slightly less used than limestone(�3 %) but, unlike the latter, was not used inmonuments but only for residential buildings and inany case during recent reconstructions.
Other sedimentary rocks, such as sandstones, areoccasionally found. This is the case of the portal ofthe Filangieri Museum (probably coming fromPunta Lagno formation, Sorrento peninsula) and thepillars of the Renaissance cloister of S. Giovanni aCarbonara church (Pietra Serena from Tuscany;Manganelli, pers. comm.)
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Figure 22. Pie-chart showing weathering grades of all thebuilding stones surveyed.
In an area characterized by large volcanic com-plexes, lavas clearly represented the natural substi-tute for Piperno s.s. in more recent residential andmonumental buildings.
On the basis of macroscopic in situ observation, itis possible to distinguish lavas of Phlegrean andVesuvian origin. The quarries in the Phlegrean area(Punta Marmolite, Cuma, Monte Olibano) wereprobably too small to supply sufficient quantities ofstone for large-scale operations such as the restora-tion of Corso Umberto I, for which a great amountof materials comes from the Vesuvian area.
The general decay of building stones is shown infigure 22, which indicates that about 80 % of thelithotypes is affected by moderate to severe weather-ing, percentages reaching up to 95 % for Piperno s.l.As already mentioned, this building material is oneof the most damaged, mainly because of its wide-spread use in parts of buildings frequently exposedto physical and chemical attack (impact, use ofpaints and plaster, pollution caused by road traffic,etc.).
5. Conclusions
Research undertaken so far has generated a con-siderable amount of data, which will be the basis forfurther detailed studies, some of which are alreadyplanned. The following considerations should there-fore be viewed as preliminary. The first and onlypartially expected conclusions deal with the distri-bution and weathering of the building stones. Asregards distribution, while lithotypes from the Phle-grean area (Piperno s.s., Campanian Ignimbrite,Neapolitan Yellow Tuff, and subordinately lavas)and Vesuvius (lavas) clearly prevail, it should benoted that NYT is limited to only a few monuments.Further knowledge on single monuments will begained by detailed studies. Particularly, it is in pro-gress a collaboration with the local Soprintendenzaai Beni Architettonici ed Ambientali of Naples andProvince on the Basilica of S. Chiara [8]. A moredetailed research on each single lithotype will aim atevaluating mineralogical, petrographical and engi-neering–geological characteristics, typologies,causes of decay, and identification of areas of prove-nance. In some cases, the same attention which isnow paid to safeguarding the stone used in architec-tural works must be devoted to the quarries fromwhich that stone came, and to their protection andpreservation. A good example is that of Piperno s.s.which, owing to its peculiar textural, technical andaesthetic characteristics, cannot be replaced by other
The state of preservation is variable; the mostcommon typologies of weathering are stains, patinæand lacking.
4. Discussion
The preceding sections clearly show that the ar-chitectural history of Naples is characterized bythree main lithotypes: Piperno s.s., Neapolitan Yel-low Tuff and lavas.
Among these materials Piperno s.s. is the mostcommon and has been used in the Neapolitan archi-tecture both as structural and ornamental elements.However, during the survey it was sometimes evi-denced the use of Piperno-like materials, at least asconcerns textural features (preferentially CampanianIgnimbrite in pipernoid facies).
A typical and documented example regards therebuilding of the Basilica of S. Chiara, for whichpipernoid tuff (CI) from Puccianello (Caserta) hasbeen used, well recognizable in the pointed arches oftwo- and three-mullioned windows.
NYT, widespread throughout the province ofNaples as cut stone, was and still is used as anarchitectural material. In the ancient city centre,there are many monuments in face-brick tuff, mostof which were built during the Angevin period,although there are some which are more recent.
There are many advantages, both strictly technicaland architectural, in using this stone (obvious exam-ples being its easy availability and workability).However, it is extremely vulnerable to deteriorationcaused by meteoric agents, both physical and chemi-cal. The effects are mainly concentrated in areaswhere water most often passed, e.g., lower parts offacings, points of contact with lithotypes of lowerporosity, etc.
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materials (pipernoid tuff, peperino or basaltina), atleast for restoring particularly fine monuments. It istherefore necessary to recover and protect the origi-nal quarries of Soccavo and Pianura, which are true‘geotopes’, important sites not only for technicalreasons, but above all for their intrinsic historicaland cultural value.
Acknowledgements. The authors gratefully ac-knowledge F. Barattolo (Federico II University ofNaples) for micropaleontological observations andC. Manganelli (CNR, France) for his helpful sugges-tions. The work was carried out with the financialsupport of Italian National Council of Research(CNR) Progetto Finalizzato ‘Beni Culturali’, con-tract number 96.01114.PF36. Thanks are due to M.Serracino (CNR, Rome) for his skills in microprobeanalyses.
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