X-ray fluorescence analysis of trace elements in silicate rocks using fused glass discs

X-ray fluorescence analysis of twelve trace elements in silicate rocks (V, Cr, Co, Ni, Rb, Sr, Y, Zr, Nb, Ba, La, Ce) was carried out by using fused glass discs prepared by mixing 0.700 g of powder rock samples with 3.150 g of lithium tetraborate and 3.150 g of lithium metaborate. The method was calibrated using one hundred and twenty-one in-house rock standards and the accuracy was tested using sixteen international rock standards. The errors range from 3 to 10% for abundances ranging from 0 to 2300 ppm. Overall, the quality of the analytical data obtained by the proposed method is similar to that one obtained by processing powder pellets. Since the samples prepared through this technique allows the determination of major elements too, with a high degree of accuracy, the proposed methodology is characterized by an excellent ratio of analytical quality and operating time

Calibration of XRF data on silicate rocks using chemicals as in-house standards

X-ray fluorescence (XRF) is an accurate, rapid spectroscopic technique for chemical element determinations on rock samples. The aim of this research was to evaluate a calibration method based on the use of suitable mixtures of chemicals. X-ray fluorescence analysis of major elements (Na, Mg, Al, Si, K, Ca, Fe) was carried out using sample-lithium borate fusion mixtures (with a 1:9 sample/borate dilution). The accuracy of the proposed calibration method was tested on twenty-four international rock standards. Results are in good or excellent agreement with the literature recommended value

Effectiveness, compatibility and durability of consolidants for marble: a review of the last ten year of researches

The choice of suitable consolidant treatment for cultural stones is one of the main challenging issue for conservation and protection of ancient masonry. Among building materials, marble is one of the most used for building and sculptures. Due to its low porosity, the assessment of suitable treatment for marble consolidation is not trivial; beside, the type of product, treatment methodology, effectiveness and compatibility investigation and durability monitoring have to be taken in great account. Recently, researchers have extensively tested and proposed new products for consolidating carbonate stones, including organic and inorganic products, nanoparticles, biological organisms (De Muynck et al., 2010). Nevertheless, no entirely satisfactory treatment is currently available for marble consolidation. At the same time, no unique evaluation criteria to use as laboratory estimators of consolidating performances have been assessed . The present paper aims to carry out a review of the state of art, based on the last ten years of researches, on consolidants for marble substrate. We summarize the different type of commercial and research products proposed for marble consolidation, by comparing also effectiveness, compatibility and durability of each proposed product, in function of consolidant features (i.e., product concentration, solvent type) and treatment methodology (application process, and contact time)

A fast and user-friendly software for quantitative chemical analysis through XRF

X-ray fluorescence (XRF) spectroscopy is a technique widely used for the study and conservation of cultural heritage materials. A Microsoft Excel spreadsheet to determine major (Na, Mg, Al, Si, K, Ca, Fe) and minor (P, Ti, Mn) elements in rocks and other materials by XRF is presented. The code is based on the analytical method proposed a few decades ago by Franzini et al., which is based on the algorithm: Ci = Ii ⋅ ΣKi,j Cj, where Ci is the concentration (expressed as wt%) of the chemical element “i”, Ii is the intensity of the characteristic line, Cj is the concentration of interfering elements, and Ki,j are experimental coefficients that account for the matrix effects (absorption and enhancement). Ki,j have the dimension of mass absorption coefficients and they may be calculated from a set of N reference samples using multivariate regression methods. The algorithm proposed by these authors is particularly suitable for processing samples prepared in the form of pressed powders. The Microsoft Excel spreadsheet allows you to: a) choose a set of reference samples (international or interlaboratory standards); b) evaluate the expected matrix effects on the basis of the XRF total mass absorption coefficients; c) calculate the correction coefficients Ki,j through multivariable regression; d) calculate the analytical accuracy and graphically represent the results; e) choose five samples (monitors) for the correction of instrumental drift. Based on these steps, the software allows you to: i) enter the analytical intensities of major and minor elements measured on the monitors and on unknown samples (the loss on ignition must be determined separately); ii) calculate the correction of the instrumental drift; iii) determine the concentration of elements and express them as wt%

The building stones of the apsidal walls of the Pisa’s Cathedral

This paper reports the preliminary data about the stones used in the apsidal walls of the Cathedral of Pisa. The research was made during the study and restoration works of the monument, under the supervision of the Opera della Primaziale Pisana. The collected data shows the prevalence of stones commonly used in the historical buildings of the city. The main lithotypes are the marbles from the Monte Pisano and from the Apuan Alps. Moreover, there are numerous ashlars of Proconnesian marble and two capitals of Pentelic and one of Paros marbles, three lithotypes used during the Roman Age and coming from the Eastern Mediterranean. The wall of the loggia of the third storey is almost entirely made up of a calcarenite (Panchina) coming from the area South of Livorno. Black limestone from the Monti d’Oltre Serchio, and serpentinite and red marly limestone outcropping in different areas of Tuscany, were also identified

Panchina Calcarenite: A Building Material from Tuscany Coast

The “Panchina” calcarenite widely outcrops along the Tuscan coastline from Livorno to Baratti (western Tuscany). It is a stone, highly porous with medium sized grains rich in organogenic carbonate fragments, mainly consisting in shells of bivalves, gastropods, and echinoderms visible to the naked eye or by using a lens. In the framework of the ongoing research on the building stones and mortars used throughout the Middle Ages in and surrounding the Pisa’s city (western Tuscany), this study focuses on the determination of the main physical and mechanical properties of “Panchina” stone samples from Livorno coast (Tuscany, Italy). The “Panchina” stone is no longer quarried and data is collected from unweathered rocks sampled from currently accessible outcrops. The data collected on twenty-eightsamples from six outcrops of the Tuscan coast showed that the analysed specimens are made up of abundant calcite, subordinate quartz and feldspars, and traces of phyllosilicates. The analysed samples are characterized by medium-high porosity, highly variable water absorption by both capillarity and total immersion at atmospheric pressure, low uniaxial compressive resistance. Thanks to the good physical and mechanical properties that characterize the stone, the “Panchina” calcarenite is easy to work and extensively used in the necropolis of the Gulf of Baratti since Etruscan times and, in medieval times, in various public and religious buildings in the city of Pisa

A contribution to the mineralogy of the Larderello geothermal field. X-ray crystallographic studies on borate minerals "bechilite" and "lagonite" and crystal structure determination of ginorite

This work reports the results of mineralogical studies on some borate minerals from the Larderello geothermal field. XRD patterns of “bechilite” and “lagonite” confirmed they actually are respectively admixtures of sassolite and ammonioborite, and of sassolite with minor santite, gypsum and larderellite. Single crystal structural study of ginorite from the type locality, Sasso Pisano (Castelnuovo val di Cecina, Pisa) confirmed its isotypism with strontioginorite. Ginorite is monoclinic, space group P21/a, with unit cell parameters a =12.7673(1) Å, b = 14.3112(11), c = 12.7298(9), β= 101.055(5)° V=2282.8(2) Å3. The refinement of its crystal structure converged to R1 = 0.058 on the basis of 3387 reflections with Fo > 4σ (Fo). Analogously to strontioginorite, ginorite crystal structure can be described in terms of complex “sheets” parallel to (010), made up by borate groups and Ca coordination polyhedra, with interlayer linkage assured by Ca cations and hydrogen bonds. The cell volume contraction of ginorite respect to strontioginorite is related to the shrinkage of Ca coordination polyhedra present in the complex Me-borate sheets

Thermal behaviour of Al-rich tobermorite

The tobermorite supergroup is composed by a number of calcium-silicate-hydrate (C-S-H) minerals characterized by different hydration states and sub-cell symmetries. Taking into account their basal spacing, closely related to the hydration state, phases having a 14 Å (plombierite), 11 Å (tobermorite, kenotobermorite, and clinotobermorite), and 9 Å (riversideite) basal spacing have been described. Tobermorite and kenotobermorite belong to the so-called tobermorite group and differ for their thermal behaviour which can be "normal" (the phase shrinks to a 9 Å phase at 300 °C) or "anomalous" (the phase preserves its 11 Å basal spacing at 300 °C). Specimens of Al-rich tobermorite from Montalto di Castro and Vallerano, Latium, Central Italy, showing a "normal" thermal behaviour, were studied in order to describe the transition from the 11 Å to the 9 Å phase by means of thermogravimetric-differential scanning calorimetry (TG-DSC) analyses as well as in situ and ex situ X-ray diffraction experiments. The TG-DSC analyses showed a continuous mass loss from 100 °C up to 700 °C, with different mass loss gradients between 100 °C up to 300 °C and between 300 °C up to 700 °C, corresponding to the dehydration of tobermorite and dehydroxylation of "tobermorite 9 A", respectively. Above 700 °C, "tobermorite 9 Å" is replaced by wollastonite. The X-ray powder diffraction data were collected at the GILDA beamline of the ESRF, Grenoble, France, from room temperature up to ca. 840 °C. Tobermorite is completely replaced by the 9 A phase at ca. 300 °C, whereas the latter is transformed into wollastonite at ca. 700 °C. The transition from the 11 Å to the 9 Å phase seems to be favoured by the transient appearance of a clinotobermorite-like compound

Mineralogical-chemical Alteration and Origin of Ignimbritic Stones Used in the Old Cathedral of Nostra Signora di Castro (Sardinia, Italy)

The pyroclastic rocks belonging to the Late Eocene-Miocene volcanic activity that occurred in Sardinia between 38 and 15 Ma ago were widely used as construction materials in several Romanesque churches of the easternmost Logudoro area, as well as in large parts of the Sardinia territory. In this work, the ancient Cathedral of Nostra Signora di Castro (twelfth century) was taken as a representative case study. There is no historical or archaeological evidence of ancient quarries. Based on the geochemical, petrographic, and volcanological data on several samples from an extensive field area (approximately 150km2), a geographical zoning of the volcanics has been recognised. In the Oschiri sector, there are three different sub-zones, which can be identified with different volcanic rocks: less fractionated rocks (Differentation Index ∼70–78); intermediately fractionated rocks (D.I. ∼76– 79); and more fractionated rocks (D.I. ∼77–82). To identify the origin of the ignimbrite rocks of the Church of Nostra Signora di Castro, two statistical methods were used: stepwise linear discriminant and canonical analysis. Moreover, to define the geochemical transformation processes induced by the alteration, a comparative study of concentrations of major and trace elements measured by XRF and SEM-EDX analyses on the surface portion and the innermost areas of the stone was made