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Per. Mineral. (2004), 73, 171-195 http://go.to/permin SPECIAL ISSUE 3: A showcase of the Italian research in applied petrology An International Journal of MINERALOGY, CRYSTALLOGRAPHY, GEOCHEMISTRY, ORE DEPOSITS, PETROLOGY, VOLCANOLOGY and applied topics on Environment, Archaeometry and Cultural Heritage Dimension and ornamental stones from the Tosco-Romagnolo and Bolognese Apennine GIUSEPPE MARIA BARGOSSI1*, FABIO GAMBERINI1, GIORGIO GASPAROTTO1, GIAN CARLO GRILLINI2 and MARTA MAROCCHI1 1 Dipartimento di Scienze della Terra e Geologico-Ambientali, P.zza di P.ta San Donato, 40126 Bologna Alma Mater Studiorum Università di Bologna 2 Geologo specialista libero professionista, via Weber, 2-Bologna ABSTRACT. — The hilly territory of the eastern RIASSUNTO. — Il territorio montano e collinare Emilia-Romagna up to the Apennine watershed, also dell’Emilia orientale e della Romagna fino allo comprising part of the Romagna Toscana, represents spartiacque appenninico, comprendente anche parte in Italy the main sandstones producer, along with the della Romagna Toscana, rappresenta, in campo Pietra Serena of Firenzuola and Marradi and the nazionale, il maggior produttore di arenaria con la Pietra Serena from the Savio valley. Minor districts, Pietra Serena di Firenzuola e di Marradi e con la not less important for the local economy are also Pietra Serena della Val Savio. Sono altresì presenti present, such as those exploiting the selenitic minori realtà produttive ma non meno importanti gypsum of Brisighella, Borgo Rivola, Borgo nell’economia locale come quelle dei gessi selenitici Tossignano, Bologna and the «Crystalline di Brisighella, Borgo Rivola, Borgo Tossignano, Bologna e dell’«Alabastro Cristallino» di Torriana, Alabaster» of Torriana, the San Marino calcarenites, della calcarenite di San Marino, del calcare del the Montefeltro limestone and the Montovolo and Montefeltro e delle arenarie di Montovolo e di Castel d’Aiano sandstones. We should not forget the Castel d’Aiano. Non va dimenticato il patrimonio historical-cultural heritage constituted by the now storico-culturale costituito dalle cave ora dismesse dismissed quarries of the Varignana, Sasso Marconi, delle arenarie di Varignana, di Sasso Marconi, di Monghidoro, Castiglione dei Pepoli and Porretta Monghidoro, di Castiglione dei Pepoli e di Porretta, sandstones, employed since the Villanovian, impiegate già in epoca villanoviana, etrusca, Etruscan, Roman, Medieval and Renaissance ages; romana, medioevale e rinascimentale. Nonché di as well as unique materials, locally employed, such materiali unici di impiego locale come il calcare di as the Montecodruzzo limestone, the Spungone Montecodruzzo, la calcarenite dello Spungone, il calcarenite, the Labante travertine, the euphotide travertino di Labante, il Gabbro eufotide e le gabbro and the Mantesca and San Zanobi Serpentiniti della Mantesca e di San Zanobi. serpentinites. Lo scopo principale degli autori non è quello di The aim of the authors is to give in this work realizzare un lavoro di ricerca riguardante la some historical elements of knowledge on geologia e la stratigrafia della zona presa in dimension and ornamental stones and not to put considerazione bensì quello di fornire alcuni forward a research work regarding the geology and elementi storici di conoscenza sui materiali lapidei stratigraphy of the area. ornamentali e da costruzione. KEY WORDS: Dimension and ornamental stones, * Corresponding author, E-mail: [email protected] quarries, petrography, employment. 172 G.M. BARGOSSI, F. GAMBERINI, G. GASPAROTTO, G.C. GRILLINI and M. MAROCCHI INTRODUCTION attributed the duty of underlining the elegance, the nobility or importance of a building. These The territory located on the eastern side of employment criteria had an even stronger the Emilia-Romagna region, in the area importance on minor buildings, where the bounded by the via Emilia axis and the Tosco- building ordinary character did not imply and romagnolo Apennine ridge, preserves justify a dismissal of the usual procedure. evidences of stone employment which since the Therefore, the stone employment was restricted Villanovian age are coming up to nowadays. to a few and precise architectural elements in All the different populations and cultures who building prospects, such as corner parastades, inhabited these regions following one another, coats-of-arms or decorative elements of some have found in the stone a proper material both kind of importance. to put into effect artistic and religious Mainly referring to and taking inspiration expressions and to build public and private from the famous work by Rodolico (1953) «Le works. The presence of stone materials in a city pietre delle città d’Italia» and restricting this normally represents the synthesis between treatment to the territory previously described, building stones occurring in the hinterland and our principal aim was collecting elements of rocks which have been imported even from geological, petrographic and mineralogical very far places. They indifferently and knowledge, together with the employment of powerfully fulfil both aesthetic tasks and locally mined dimension stones, and to structural requirements. investigate the deterioration phenomena these As far as we consider the cities examined in materials have suffered since they have been this paper, from Bologna to Imola, Faenza, employed in the urban environment. We think Forlì, Cesena up to Rimini, the most common that the arguments we collected in this paper building materials are sandstones, selenites and could help earth scientist and cultural heritage limestones, coming from nearby quarries and estimators to better understand the relationship therefore easy to be found with reasonable existing between these cities and the purchase and transportation costs. Besides these «poor» materials, stones coming from the surrounding land, and that a careful utilization Venetian and Istrian quarries are harmoniously of georesources can produce a general associated. The thick canal network connecting enrichment both economic and cultural. these cities to the Adriatic sea and to the Po river, together with the via Emilia and Romea, made it possible for these materials to be LIST OF ORNAMENTAL STONES: GEOLOGY, brought in large amounts and then employed PETROGRAPHY AND HISTORICAL EMPLOYMENT mainly in factories with «very rich economy» and in important public buildings. As stated The terrains outcropping in the investigated before, these were very expensive materials; area (Fig. 1) are mainly represented by clastic we should remember that such an important sedimentary rocks and subordinately by site as San Petronio, wanted by all the city evaporitic and carbonatic rocks while only a inhabitants and by the powerful art very small part consists of ophiolites. corporations of Bologna, was never completed, The rocks which have been mined in the past not even the façade covering, due to the high and are nowadays mined in the active quarries materials’ costs, here, more precisely, referring of the Santerno and Savio river valleys, to the Istrian stone, to the white and red represent an important georesource for these limestones from Verona and to the Candoglia mountain territories; they will be described marbles. To the stone, employed in portals, in according to a chronological order referring to architectural frameworks, in capitals, in carved the geological age of the belonging formation cornices, in doors and windows fastigia, was (Società Geologica Italiana, 1990). Dimension andornamentalstonesfromtheTosco-RomagnoloBologneseApennine 173 Fig. 1 – Geological map showing the lithotypes outcropping in the investigated area and the main quarries we cited in the text (Modified after Bargossi et al., 2001). 174 G.M. BARGOSSI, F. GAMBERINI, G. GASPAROTTO, G.C. GRILLINI and M. MAROCCHI A) The Sasso della Mantesca gabbros and serpentinites (Bologna) GEOLOGICAL SETTING Gabbros and serpentinites belonging to the Vara Supergroup ophiolites (external Liguride Domain), of Jurassic age, outcrop between the Idice and Sillaro river valleys scattered in the undifferentiated Chaotic Complex better known as «Argille Scagliose». These rocks, much more compact than the highly disrupted clays which include them, give rise to small relieves called «Sasso della Mantesca» and «Sasso di San Zanobi» (Grillini, 1977). Fig. 2 – Photomicrograph of euphotide gabbro (Sasso della MINING ACTIVITY Mantesca); the lower part is made up of serpentinized clinopyroxene diallage, the upper part of albitized Mining activity in the «Sasso della plagioclase (N//). Mantesca» area in the watershed from the Sillaro and Idice valleys has gone on until 1940 and regarded the well known «euphotide» Gabbro, the «ranocchiaia Serpentinite» and the «serpentinitic Breccia». MINERALOGICAL-PETROGRAPHIC CHARACTERS Euphotide Gabbro It’s a grey-greenish gabbro, coarse-grained (up to some centimetres) with granular hypidiomorphic structure made up of albitized plagioclase crystals in which prehnite and chlorite plagues and veins, clay minerals’ granulations and strongly foliated, often chloritized and serpentinized clinopyroxene (diallage) are present. Relicts of totally serpentinized olivine have also been detected. Fig. 3 – Photomicrograph of serpentinite (Sasso della The main accessory phases are represented by Mantesca) showing the typical cellular structure (N//). ilmenite, hematite and apatite (Fig. 2). Serpentinites green-coloured chrysotile filling fractures and They show cellular structure with large veins