Carrara Marbles Research Articles

Analytical Investigation of Iron-Based Stains on Carbonate Stones: Rust Formation, Diffusion Mechanisms, and Speciation

In cultural heritage, unaesthetic stains on carbonate stones due to their close contacts with metals are of concern for the preservation of sculptures, monumental facades and archeological finds of various origin and antiquities. Rust stains made up of various oxidized iron compounds are the most frequent forms of alteration. The presence of ferric iron on rust-stained marble surfaces was confirmed in previous studies and oriented the choice of the best cleaning method (based on complexing agents specific for ferric ions). However, the composition of rust stains may vary along their extension. As the corrosion of the metallic iron proceeds, if the oxygen levels in the surroundings are low and there are no conditions to favor the oxidation, ferrous ions can also diffuse within the carbonate structure and form a variety of intermediate compounds. In this study, the iron stains on archeological marbles were compared with those artificially produced on Carrara marbles and Travertine samples. The use of integrated techniques (optical and scanning electron microscopy as well as Mössbauer and XPS spectroscopy) with complementary analytical depths, has provided the overall information. Rust formation and diffusion mechanisms in carbonates were revealed together with the evolution of iron speciation and identification of phases such as ferrihydrite, goethite, maghemite, nanomagnetite, and hematite.

An innovative approach for provenancing ancient white marbles: the contribution of x-ray diffraction to disentangling the origins of G\xf6ktepe and Carrara marbles

The paper presents a very efficient, quick, low-cost and minimally micro-destructive approach to discriminating between Roman artefacts sculpted with Göktepe (Aphrodisia, Turkey) or Carrara (Apuan Alps, Italy) white marbles by using a standard X-Ray Powder Diffractometer (XRPD) and a refinement of the unit cell parameters and volume of calcite. At present, the routine way of differentiating between these two almost indistinguishable by-eye marbles is based on the typically higher strontium content of calcite in the Microasiatic lithotype, a unique geochemical-crystallographic feature with respect to all other non-Göktepe fine-grained white marbles used in classical times. The XRPD approach has been verified by testing eighteen samples of known composition, nine from Carrara and nine from Göktepe quarries, which had already been analysed with other laboratory techniques. The applicability of the method to archaeological artefacts was confirmed by an archaeometric study performed on some famous Roman sculptures of the National Archaeological Museum of Venice and from Hadrian’s Villa at Tivoli. The results show that Göktepe/Carrara discrimination is always possible and that this XRPD approach can potentially become a useful and low-cost routine procedure to solve provenance issues.

“So Close to the Banks of Oblivion” An American Master is Rediscovered

Inattention has doomed too many masters. Without provenance, context or an appreciation for cultural continuity, artistic treasures become disposable bric‐a‐brac. And so it nearly was for two companion bianco Carrara marbles that had lain unattested for decades in the storage of a small Idaho museum. Now proven by extensive research to be the works of sculptor Madison Colby (1842‐1871), the 19‐inch rondels bespeak a talent abruptly silenced by tuberculosis but not too soon to escape the notice of the San Francisco and Chicago art communities. Having experienced this resurrection, Colby's undeniable skill but sadly limited catalog can once again enjoy a deserved acclaim.

Systematic alteration survey and stone provenance for restoring heritage buildings: Punta Begoña Galleries (Basque-Country, Spain)

Punta Begoña Galleries (Getxo, Spain) are a fine example of early twentieth century architectural heritage. Built during the early years of reinforced concrete usage, they were decorated inside with ornamental stones to project an image of exclusivity and luxury. After years of neglect, it is essential to characterise construction materials, including the determination of their origin, current state of conservation and restoration options, before undertaking a recovery project respectful with the original edifice. With this aim, a detailed study was made of the current state of conservation of the lithologies that decorate the salon of the building using an alphanumerical matrix of alterations to define the type of existing disturbances and assess their intensity. Complementarily, a petrological, isotopic and mineralogical study of these materials was made in order to determine their provenance. They include Carrara marbles and a local limestone (Red Ereño) which was internationally renowned, in particular being used in buildings such as St. Peter's Basilica in the Vatican. In this paper a first complete description of this stone has been made. By combining the two sources of information, guidance on the most appropriate restoration options in each case is given. The option of polishing materials includes a specific study of the degree of wear. By means of which it is verified that small wear (<350 μm) is sufficient to produce high gloss values (100GU).

Thermal degradation in Carrara marbles as the cause of deformation of cladding slabs

Marble slabs, typically used as façade panels to externally cover buildings, might permanently deform after a certain time of environmental exposure. This phenomenon, called bowing, is generally accompanied by a reduction of strength which increases with increasing degree of bowing. In the present paper, a theoretical model to calculate the progressive bowing of marble slabs submitted to temperature cycles is briefly recalled and applied to a specific Carrara marble sample. The marble is investigated by a microscopic analysis of thin sections cut along three orthogonal directions. The digital photographs are treated by an image analysis code which is capable of extracting grain size and shape distributions. In this way the anisotropic microstructure of the marble is quantified and taken into account in the numerical analyses. The influence of size distribution of grains as well as of their distribution of optic axis orientation on the slab bowing is discussed with the attempt of offering a quantitative tool for a better understanding of in situ bowing measurements.

Conditions for veining and origin of mineralizing fluids in the Alpi Apuane (NW Tuscany, Italy): Evidence from structural and geochemical analyses on calcite veins hosted in Carrara marbles

This work deals with structural and geochemical (chemical and isotopic) analyses of calcite veins hosted in Carrara marbles in the Alpi Apuane, NW Tuscany, Italy. Geometric features and spatial distribution of veins provided estimations of stress ratio (Φ = (σ2 − σ3)/(σ1 − σ3)), driving stress ratio (R′ = (Pf − σ3)/(σ1 − σ3)) and fluid overpressure (Δsi = Pf − σ3) at the time of vein formation. The obtained values of Φ = 32 and R′ = 0.43 reveal that fluid pressure was higher than the intermediate principal stress at the time of veins formation, whereas the estimated Δsi ranging from 129 to 207 MPa indicates that veins formed under supra-hydrostatic to lithostatic pressure conditions. Carbon (δ13CV-PDB = 1.81–2.10‰ for veins and 1.95–2.51‰ for host marbles), oxygen (δ18OV-SMOW = 28.71–29.57‰ for veins and 28.90–29.36‰ for host marbles) and strontium (87Sr/86Sr = 0.707716–0.707985 for veins and 0.0707708–0.707900 for host marbles) isotope compositions in vein/host marble pairs were internally quite consistent. Combining our structural and geochemical data, a modeling approach was performed to investigate the compositional features and temperatures of calcite depositing fluids. The results of our studies give evidence that (1) pore-fluids in Carrara marble, consisting of metamorphic formation waters, were re-mobilized during veining event and migrated within the veins in closed system conditions, (2) veins formed after ductile folding phases and before high-angle brittle faulting events, at temperature and pressure around 250 °C and 210 MPa, and finally (3) about 12 g H2O/m3 marble are calculated to have been available as vein parental fluid at the time of vein formation.

Selected examples of natural stones from Italy and Germany used in architectural objects in Krakow – a short geological excursion

The aim of the following paper is to propose a trip to selected sites in Kraków where decorative stones imported from Italy and Germany were used. The main types of stones are presented together with their commercial names, quarries, age and decorative values. Additionally, the author identified the regions in Italy and Germany from which stones were supplied. The most popular Italian decorative stones are the Carrara marbles quarried in the vicinity of Carrara and the “Ammonitico rosso” limestones extracted in the neighbourhood of Verona. Interesting are also porphyries from Trident, limestones from Brescia, travertines from Tivoli and granites and travertines quarried in Sardynia. In Germany large deposits of Upper Jurassic limestones are located in northern Bavaria (Franconia).

The Carrara Marbles (Alpi Apuane, Italy): a geological and economical updated review

The Carrara Marbles (Alpi Apuane, Italy): a geological and economical updated review

Microfabric study on the deformational and thermal history of the Alpi Apuane marbles (Carrara marbles), Italy

Marbles from different geometrical and structural positions within the Alpi Apuane metamorphic complex show a large variability in microfabric types as indicated by microstructure, c-axis orientation and temperature analysis. Statically recrystallized samples showing a granoblastic microstructure and polygonal grain boundaries are characterized by a grain size variation from east to west from 80–100 μm to 250–300 μm. This is correlated with an equilibration calcite-dolomite temperature from 360–380°C to 420°–430°C. Two kinds of dynamically recrystallized microstructures have been investigated: a first one exhibiting coarse grains (150–200 μm) with lobate grain boundaries and a strong shape preferred orientation and a second one characterized by a smaller grain size (40–50 μm) and predominantly straight grain boundaries. These microstructural types, associated with localized post-thermal peak shear zones and meter- to kilometer-scale folds, are interpreted as related to high strain and high temperature crystal plastic deformation mechanisms (dislocation creep) associated with predominant grain boundary migration (type-B1) or subgrain-rotation recrystallization (type-B2). These differences in dynamically recrystallized microstructures are related to equilibration temperatures higher in type-B1 (390°C) than in type-B2 (370–340°C). We have been able to relate the development of the different microfabric types to the successive stages of deformation of the Alpi Apuane metamorphic complex.

Fabric anisotropy and its influence on physical weathering of different types of Carrara marbles

To evaluate the texture-controlled part on the thermally induced degradation of marbles, the anisotropic thermal dilatation was calculated from texture analyses of four exemplary samples from the Carrara area in Italy and compared to experimentally measured dilatation coefficients. The thermal dilatation as determined in the experiment is controlled by an intrinsic part (anisotropic single crystal properties and texture) and an extrinsic part (e.g. thermally induced microcracks). As expected from theoretical calculations, there is a correlation between the strongest dilatation and the c-axis maxima and the weakest dilatation and the a-axis maxima according to the single crystal data of calcite. However, a quantitative correlation could not be established. Obviously, other fabric parameters like the grain size, grain shape anisotropies, grain boundary geometries and microcrack formation during heating modify the texture-controlled part significantly. After thermal treatment up to 130°C, all samples show a residual strain. However, the magnitude and directional dependence is remarkably different and is unequivocally correlated to both the microstructure and the texture. Since the number of parameters controlling the physical weathering is very large, a comprehensive quantification of fabrics is indispensible for the understanding of thermally controlled degradation processes of physical weathering in marbles.

Fluid circulation in the Apuane Alps core complex: evidence from extension veins in the Carrara marble

Abstract In the Apuane Alps (AA) metamorphic core complex, syn-metamorphic mineral deposits are mainly restricted to extensional shear zones in the Lower Plate Palaeozoic basement. By contrast, the extension structures at upper levels, such as the detachment fault, that are typically the seat of fluid circulation and mineralization in other core complexes, are barren in the AA. Extension veins hosted by the Jurassic Carrara marbles are among the few examples of (minor) mineralization located in the upper levels of the AA core complex. Calcite–dolomite geothermometry and fluid inclusion data suggest that the mineralizing process in these veins began under pressure (P)-temperature (T) conditions close to the metamorphic peak (about 400°C, 3 kbar). Progressive cooling and mixing between metamorphic and late stage meteoric fluids were probably responsible for most of the mineral deposition. Batches of relatively saline fluids presumably resulted from interaction with evaporitic levels located along the detachment fault. In agreement with previous estimates, fluid inclusion constraints on the P—T synmetamorphic path of the AA suggest a relatively rapid cooling of the core complex as a result of uplift. However, the maximum estimated geothermal gradient (about 35°C/km) is considerably lower than in other core complexes, where large-scale hydrothermal circulation was associated with extension and uplift. Hence, in the AA, fluid circulation at shallow levels and mixing among fluids of different origin were not favoured, thus precluding the formation of mineral deposits along major extensional structures.

CONSERVATION OF SCULPTURAL STONEWORK: VIRGIN &amp; CHILD ON S. MARIA DEI MIRACOLI AND THE LOGGETTA OF THE CAMPANILE, VENICE

This report describes the methods used to consolidate and protect the marble Virgin and Child on the facade of S. Maria dei Miracoli, Venice, and the stones used in the Loggetta of the Campanile: Carrara, Greek and Verona marbles and Istrian stone.

The Geological Survey of Italy

MY friend Mr. W. Topley, in his interesting account of the Italian Geological Survey (NATURE, vol. xxv. p. 86), is quite right when he states that the geological surveyors seem now to have definitely fixed the position of the Carrara marbles in the Trias. If, however, he means to imply that the geological world at large will accept this decision, I fear he is mistaken. The patient toil, spread over many years, and carried on by M. Coquand with more than due regard to Buffon's advice to geologists, “Il faut voir beaucoup et revoir souvent,” gives him such authority when speaking on the structure of the Apuan Alps and he Campigliese, that nothing but the most absolute proof that he is wrong in regarding the metamorphic marbles of Carrara, as well as those of the Pyrenees (St. Béat, &c.), as being of Carboniferous age, will prevent foreign students of Italian geology from accepting his views on the matter. I have read, I think, all that has been written in Italy by De Stefani and others on the point in question since the publication in full of M. Coquand's mature conclusions in the Bulletin de la Société géologique de France, in 1874, and I still regard his position as entirely unassailed. In 1876 I published in the Geological Magazine a short résumé of M. Coquand's results, to which I would refer any who are interested in the subject.