Ricerc@Sapienza

Natural Mg-rich lucchesiite was thermally treated in air and hydrogen atmosphere up to 800 °C to study potential changes in Fe-, Mg- and Al ordering over the octahedrally coordinated Y- and Z-sites, and to explore possible applications to intracrystalline geothermometry based on tourmaline. Overall, the experimental data (structural refinement, Mössbauer, infrared and optical absorption spectroscopy) show that thermal treatment of lucchesiite results in an increase of Fetotcontents at Z balanced by an increase of Mg and Al at Y.

Tourmalines form the most important boron rock-forming minerals on Earth. They belong to the
cyclosilicates with a structure that may be regarded as a three-dimensional framework of octahedra ZO6
that encompass columns of structural “islands” made of XO9, YO6, BO3, and TO4 polyhedra. The overall
structure of tourmaline is a result of short-range and long-range constraints resulting, respectively on the
charge and size of ions. In this study, published data are reviewed and analyzed to achieve a synthesis

Ettringite, reported with ideal formula Ca6Al2(SO4)3(OH)12·26H2O, is recognized as a secondary-alteration mineral and as an important crystalline constituent of Portland cements, playing different roles at different time scales. It contains more than 40 wt% of H2O. The crystal structure and crystal chemistry of ettringite were investigated by electron microprobe analysis in wavelength-dispersive mode, infrared spectroscopy, and single-crystal neutron diffraction at 20 K.

We investigated by a multi-analytical approach (Brillouin scattering, X-ray diffraction and electron microprobe) the dependence of the elastic properties on the chemical composition of six spinels in the series (Mg1−x,Fex)Al2O4(0 ≤ x ≤ 0.5). With the exception of C12, all the elastic moduli (C11, C44, KS0and G) are insensitive to chemical composition for low iron concentration, while they decrease linearly for higher Fe2+content. Only C12shows a continuous linear increase with increasing Fe2+across the whole compositional range under investigation.

Twenty natural spinel single crystals displaying colors almost representative for the entire spinel variability were investigated by electron microprobe and UV–VIS–NIR–MIR and FTIR spectroscopies. Eight of them, selected among the Fe-bearing ones, were also analyzed by X-ray diffraction, and five by Mössbauer spectroscopy to obtain information on the oxidation state and site distribution of Fe.

Eruptions of Sinabung volcano, Indonesia have been ongoing since 2013. Since that time, the character of eruptions has changed, from phreatic to phreatomagmatic to magmatic explosive eruptions, and from production of a lava dome that collapsed to a subsequent thick lava flow that slowly ceased to be active, and later, to a new lava dome. As the eruption progressed, event trees were constructed to forecast eruptive behavior six times, with forecast windows that ranged from 2. weeks to 1.

Surface reactivity of a fibrous tremolite sample from Castelluccio Superiore (Italy) was investigated by means of free radical generation following incubation in H2O2solution buffered at pH 7.4, for several time points, ranging from 1 day to 1 month. Results obtained were compared with those of another fibrous tremolite sample (from Maryland, USA), with much smaller surface area. Structural, morphological, and chemical alterations induced on tremolite by incubation were investigated by HR-TEM/EDS.

The present paper reports the results of a mineralogical and petrographic study focused on the archaeometric characterization of Early Bronze Age pottery from the archaeological site of Khirbet al-Batrawy (Jordan), dated between 3000 and 2000 BC. Optical microscopy (OM) and X-ray powder diffraction (XRPD) analyses are used to define the nature of the raw material, the technology of the ceramic production and their developing during the centuries.

The use of Rayleigh wave ellipticity has gained increasing popularity in recent years for investigating earth structures, especially for near-surface soil characterization. In spite of its widespread application, the sensitivity of the ellipticity function to the soil structure has been rarely explored in a comprehensive and systematic manner. To this end, a new analytical method is presented for computing the sensitivity of Rayleigh wave ellipticity with respect to the structural parameters of a layered elastic half-space.