Search results for " Mineralogia"

Synthetic and natural chromium bearing spinels: an optical spectroscopy study

2014

Four samples of synthetic chromium-bearing spinels of (Mg, Fe2+)(Cr, Fe3+)2O4 composition and four samples of natural spinels of predominantly (Mg, Fe2+)(Al, Cr)2O4 composition were studied at ambient conditions by means of optical absorption spectroscopy. Synthetic end-member MgCr2O4 spinel was also studied at pressures up to ca. 10 GPa. In both synthetic and natural samples, chromium is present predominantly as octahedral Cr3+ seen in the spectra as two broad intense absorption bands in the visible range caused by the electronic spin-allowed 4A2g → 4T2g and 4A2g → 4T1g transitions (U- and Y-band, respectively). A distinct doublet structure of the Y-band in both synthetic and natural spine…

Volcanogenic particulates and gases from Etna volcano (Italy)

2014

Primo contributo sui depositi argillosi a terra rossa dell'Abisso del Vento, Isnello (PA).

2004

Secondary minerals from halite caves in the Atacama Desert (Chile)

2017

In the past 15 years several expeditions by French, American and especially Italian cavers have surveyed over 15 km of salt cave passages in the Cordillera de la Sal, close to San Pedro de Atacama village (Atacama Desert, Northern Chile). Over 50 caves have been explored up to now at an elevation around 2,500 m asl. These karst systems are characterized by in-cave temperature of around 17 °C and a relative humidity always very low, with a maximum of 15%. This extreme aridity is due to the severe conditions of the area with only a couple millimeters annual rainfall and several years without rain. Currently the rare precipitation events are enough to allow the dissolution of the salt rock and…

Hypogenic caves of Sicily (Southern Italy)

2013

First results of a study on hypogenic caves in Sicily are presented. Inactive water-table sulphuric acid caves and 3D maze caves linked to rising of thermal waters rich in H2S were recognized. Cave patterns are guided by structural planes, medium and small scale morphological features are due mainly to condensation-corrosion processes. Calcite and gypsum represent the most common cave minerals. Different types of phosphates linked to the presence of large bat guano deposits were analyzed.

Synthesis and characterization of taylor-made organo-clays for biotechnological applications

2014

Potentially harmfull elements accumulation in fumarolic alteration products at three hydrothermal systems of Greece

2018

Samples of efflorescences and encrustations of hydrothermal origin have been collected at three fumarolic areas in Greece. The three sites are Sousaki, Thiafi (Methana) and Kokkino Nero (Kos) and all belong to the South Aegean Active Volcanic Arc. Samples were analysed for their mineralogical (XRD and SEM-EDS) and chemical composition. Solutions obtained from both mineralization with HNO3 and leaching with distilled water, were analysed for major (ICP-OES), minor and trace metals (ICP-MS) and for sulfate contents (IC). Results show that their composition is mainly controlled by the petrological composition of the substrate (ultramafic rocks at Sousaki, felsic volcanic rocks at Methana and l…

A computational study of point defects and diffusion in enstatite

2009

In order to contribute to the understanding of diffusion processes in enstatite (Mg2Si2O6), we have used atomistic simulation techniques to study point defects in this mineral. We present results for a variety of Scottky and Frenkel defects of all atomic species present in it. We have furthermore calculated the activation energy for magnesium diffusion. We break diffusion down into a succession of hops between neighboring sites. Each hop is associated with a migration energy barrier. By making a series of hops, the diffusing ion may cross the unit cell. The maximum migration energy necessary to attain movement in a direction is the activation energy for diffusion in that direction. The defe…

The use of moss-bags technique to volcanic aerosols investigation on Mt. Etna (Italy)

2014

Computational study of defects in ideal phengite

2009

Phengite is the name of a series designating the “potassic dioctahedral micas between, or close to, the joins muscovite-aluminoceladonite and muscovite-celadonite” (Rieder et al. 1998). These micas play a important role in most petrogenetic reactions occurring in high-pressure (HP) metamorphic environments; they are useful geothermobarometers and participate in reactions as H2O carriers in the subduction zone. In this work we have employed atomistic simulations techniques to model defects, evaluate the most stable defect species and determine the most likely diffusion mechanism in crystals. We have calculated the defect formation energies for vacancies, impurities and interstitials, Frenkel…