Girolamo Belardi

Structural features in Tutton’s salts K2[M2+(H2O)6](SO4)2, with M2+ = Mg, Fe, Co, Ni, Cu, and Zn

Abstract The crystal chemistry of six crystals of general formula K2[M2+(H2O)6](SO4)2, with M2+ = Mg, Fe, Co, Ni, Cu, and Zn, was investigated by single-crystal structure analysis to determine the effects of the chemical variation of M2+ on the structural environment surrounding K, M, and S sites. Results indicate that the distortion in the SO4 tetrahedron and the MO6 octahedron is very small, except for CuO6 where it is pronounced because of the Jahn-Teller effect. The KO8-octacoordinate polyhedron has the highest degree of distortion, and its idealized shape may be referred to as a bicapped trigonal prism. The SO4 size is not affected by changes in cation occupancies at the adjacent M site. In contrast, changes in the KO8 size, which are accompanied by changes in the bond valence sum at K, depend on interaction with the first and second coordination sphere of M. This interaction results by changes in M-O individual lengths, by expansion of the second coordination sphere of M, and by changes in the distribution of the bond strengths over the O atoms coordinated to K. The MO6 size follows the expected trend from the increased ionic radius at the M site. The latter is also correlated with the unit-cell volume except for the Cu- and Mg-phase, which show a larger cell volume with respect to that expected. Although the relevant octahedral distortion around the Cu2+ cation explains the volume excess in the Cu-phase, an expansion of the second coordination sphere of Mg2+, compared to those of cations of larger ionic radius (such as Zn and Co), explains the excess of the unit-cell volume in the Mg-phase. As the CuO6 distortion can be caused by the Jahn-Teller effect, the higher ionicity of the Mg atom could be the cause for its anomalous behavior observed in Tutton’s salts. This stereochemical behavior of the Mg atom seems to be consistent with the weakening of the hydrogen bonds in the structure connected to differences in the bonding character of Mg and transition metals when coordinated by water molecules.

Crystal chemical and structural characterization of fibrous tremolite from Susa Valley, Italy, with comments on potential harmful effects on human health

Abstract This study is part of a broad research project devoted to the “amphibole fibers environmental problem” as related to the proposed excavation of the Susa Valley railway tunnel. In this locality, tunnel excavations are planned through metamorphic formations containing amphibole asbestos minerals, and this may give rise to worker health and public environmental issues. The Susa Valley tremolite shows a marked fibrous character, a small reduction of fiber size under grinding, and a consistent increase of the surface area. From the toxicological point of view, such tremolite fibers have been shown to be very effective in the generation of reactive oxygen species. They exhibit a very high cellular reactivity as a consequence of their morphology, structure, and crystal chemistry. Results of combined electron microprobe analysis, Mössbauer spectroscopy, and parallel-beam X-ray powder diffraction are reported for fibrous tremolite from a serpentine-schist from the “Unità Oceanica della Bassa Val di Susa” collected near Condove, Susa Valley, Italy. Data indicate that Fe2+ (84% of Fetot) is located at both the (M1 + M3) and M2 sites and that Fe3+ is at M2, in an approximate 3:2:1 ratio, respectively. No evidence of a split M4 site has been observed. The presence of M1+M3Fe2+ is confirmed by FTIR spectroscopy to be distributed 70% at M1 and 30% at M3. Both the composition (Ca1.95K0.01Na0.05)Σ2.01 (VIAl0.01Fe3+0.02Fe2+0.11Mg4.84Mn0.02)Σ5.00Si8.00O22(OH1.96F0.03Cl0.01)Σ2.00 and the cell volume 907.37(1) Å3 of the fibers are close to those expected for end-member (Ca/Mg = 2/5) tremolite.

Asbestos fibre identification vs. evaluation of asbestos hazard in ophiolitic rock mélanges, a case study from the Ligurian Alps (Italy)

In recent years, the high incidence of harmful health effects through inhalation of airborne asbestos from amphibole-bearing rock mélanges has been thoroughly documented. Here, we present a field-based, multi-scale geological approach aimed at illustrating the occurrence of amphibole fibrous mineralisation in an ophiolitic suite from the Ligurian Alps (Italy) and discussing the implication on in situ determination of the asbestos hazard. The rock mélange is composed of plurimetre-sized blocks of different lithotypes (metagabbro, serpentinite, chloritoschist) juxtaposed by the meaning of tectonic structures. The geological-structural survey revealed that the fibrous mineralisation is localised in specific structural sites of the rock volume, including veins and schistosity. Both micro-chemical and crystal structure analyses on selected fibrous samples revealed that actinolite fibres grow in veins within the metagabbro and in chloritoschists, while fibrous tremolite occurs in serpentinite schistosity. The morphological features of these amphibole fibres have been analysed in TEM images and used for classifying them as “asbestiform” or “non-asbestiform”. The results show that the asbestos hazard determination is not unequivocally identified when different procedures for asbestos fibre identification and classification are applied. This may have impact on normatives and regulations in defining environmental hazards due to asbestos occurrence.

The assessment of particulate matter emitted from stone-crushing industry by correlating rock textures with particles generated after comminution and dispersed in air environment

The generation and emission of particulate matter from abrasion industry are subjects of the pollution monitoring by multidisciplinary study involving earth sciences and engineering disciplines. This work investigates the correlation between textural properties of in situ rock with class size distribution and morphology of particles generated after rock comminution and particles emitted in the air. A special comminution-dust sampling architecture was realised. The combined use of scanning electron microscopy and particle size analyser was considered in performing digital image analysis on both crushed products and airborne particles collected onto membrane filters. The results show that the size and morphology of crushed particles are linked to the petrographic rock properties. In particular, particles with fibrous morphology are prominent in rocks showing foliated textures where elongated minerals occurred, with implication for asbestos-bearing rocks. For what concerns the airborne particles, the results show that their aerodynamic diameters are independent of the crusher operating conditions. External parameters probably intervene in the distribution of the airborne particles emission, including the dynamic air fluxes, or environmental conditions. By applying mathematical models, the morphology and size range of airborne particles following the comminution processes can be predicted, and results has implication for pollutants contamination due to particulate matters emitted by crush stone industry.

Tectonic structures and commercial compartments in active quarrying: a case history from northern Italy

By studying a quarried site exposed in the Ligurian Alps (northern Italy), this work aims to assess the impact of the tectonic structures on the exploitable rock volume characteristics/properties and, more in general, on the three-dimensional quarry architecture for its future exploitation. A field-based, multidisciplinary dataset has been integrated within a 3D geological model performed in a Geographical Information System (GIS) environment. The spatial distribution, geometry, and internal fabric of the main tectonic structures (mainly represented by faults and fracture networks) have been recognised as responsible for a structural compartmentalisation within the study area. In situ geomechanical measurements (uniaxial strength by using a Schmidt hammer) have been compared with distribution of the tectonic structures. A simulation of the influence of the tectonic structures on the rock mechanical behaviour has been performed in GIS. We conclude that occurrence of tectonic structures determines a first order degree in geodiversity at quarried sites, influencing both intrinsic (lithology and petrography) and secondary (mechanical) properties of the excavated rock volume. Consequently, understanding and reconstructing the deformation style and intensity of the tectonic setting constitute a further geological exploration criterion for assessing strategy of rock excavation and exploitation. The identification of tectonic structures is relevant to face frequently documented problems in active quarrying, such as mass movement and slope failure, reduced rock-mass quality, or non-exploitable quarry domains.

Multi-scale geological evaluation for quarrying activities in ophiolitic rocks: implications for asbestos-related legislation

This study illustrates the importance of undertaking a multi-scale geological approach when assessing ophiolites which may contain harmful asbestos. A case history from an active quarry in the Carinthia region of Austria is presented. The data obtained indicated four main zones within the heterogeneous rock mass. The study identified those horizons which could be used for commercial purposes, notably railway ballast and road sub-base. Extensive testing was undertaken which confirmed that asbestiform amphiboles were not present in the quarry. Attention is drawn to the ambiguities in current legislation regarding the presence of asbestos.RésuméCette étude illustre la nécessité de mettre en œuvre une approche géologique multi-échelle pour évaluer le contenu en amiantes nocives dans un massif d’ophiolites. Une étude de cas provenant d’une carrière en activité dans la région de Carinthie en Autriche est présentée. Les données obtenues ont indiqué l’existence de quatre zones principales au sein du massif rocheux. L’étude a permis d’identifier les horizons qui pourraient être utilisés à des fins commerciales, notamment comme ballast de voie ferrée et couche de base de route. De nombreux tests ont été réalisés. Ils ont confirmé que les amphiboles asbestiformes n’existaient pas dans cette carrière. L’attention est attirée sur les ambiguïtés de la législation actuelle concernant la présence d’amiante.