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).

Experimental measurements of the viscosity and melt structure of alkali basalts at high pressure and temperature.

Volcanic eruptions are shallow phenomena that represent the final stage of density- and viscosity- driven processes of melt migration from source rocks at upper mantle depths. In this experimental study, we investigated the effect of pressure (0.7-7.

Phlogopite-pargasite coexistence in an oxygen reduced spinel-peridotite ambient.

The occurrence of phlogopite and amphibole in mantle ultramafic rocks is widely accepted as the modal effect of metasomatism in the upper mantle. However, their simultaneous formation during metasomatic events and the related sub-solidus equilibrium with the peridotite has not been extensively studied. In this work, we discuss the geochemical conditions at which the pargasite-phlogopite assemblage becomes stable, through the investigation of two mantle xenoliths from Mount Leura (Victoria State, Australia) that bear phlogopite and the phlogopite + amphibole (pargasite) pair disseminated in a harzburgite matrix.

Diamond-inclusion system recording old deep lithosphere conditions at Udachnaya (Siberia).

Diamonds and their inclusions are unique fragments of deep Earth, which provide rare samples from inaccessible portions of our planet. Inclusion-free diamonds cannot provide information on depth of formation, which could be crucial to understand how the carbon cycle operated in the past. Inclusions in diamonds, which remain uncorrupted over geological times, may instead provide direct records of deep Earth's evolution.

Iron from a geochemical viewpoint. Understanding toxicity/pathogenicity mechanisms in iron-bearing minerals with a special attention to mineral fibers.

Iron and its role as soul of life on Earth is addressed in this review as iron is one of the most abundant elements of our universe, forms the core of our planet and that of telluric (i.e., Earth-like) planets, is a major element of the Earth's crust and is hosted in an endless number of mineral phases, both crystalline and amorphous.

Surface reactivity of amphibole asbestos: a comparison between crocidolite and tremolite.

Among asbestos minerals, fibrous riebeckite (crocidolite) and tremolite share the amphibole structure but largely differ in terms of their iron content and oxidation state. In asbestos toxicology, iron-generated free radicals are largely held as one of the causes of asbestos malignant effect. With the aim of clarifying i) the relationship between Fe occurrence and asbestos surface reactivity, and ii) how free-radical generation is modulated by surface modifications of the minerals, UICC crocidolite and fibrous tremolite from Maryland were leached from 1 day to 1 month in an oxidative medium buffered at pH 7.

The chemical environment of iron in mineral fibres. A combined X-ray absorption and Mössbauer spectroscopic study.

Although asbestos represents today one of the most harmful contaminant on Earth, in 72% of the countries worldwide only amphiboles are banned while controlled use of chrysotile is allowed. Uncertainty on the potential toxicity of chrysotile is due to the fact that the mechanisms by which mineral fibres induces cyto- and geno-toxic damage are still unclear. We have recently started a long term project aimed at the systematic investigation of the crystal-chemistry, bio-interaction and toxicity of the mineral fibres.

Iron topochemistry and surface reactivity of amphibole asbestos: relations with in vitro toxicity.

Chemical reactivity of asbestos tremolite from Italy and USA localities and Union Internationale Contre le Cancer (UICC) crocidolite was studied in relation to Fe content, oxidation state, and structural coordination. Direct correlation between amount of Fe(2+) at the exposed M(1) and M(2) sites of the amphibole structure and fiber chemical reactivity was established. The in vitro toxicity of the same samples was investigated on human alveolar A549 cell line.

Combined use of X-ray photoelectron and Mössbauer spectroscopic techniques in the analytical characterization of iron oxidation state in amphibole asbestos.

Asbestos fibers are an important cause of serious health problems and respiratory diseases. The presence, structural coordination, and oxidation state of iron at the fiber surface are potentially important for the biological effects of asbestos because iron can catalyze the Haber-Weiss reaction, generating the reactive oxygen species *OH. Literature results indicate that the surface concentration of Fe(III) may play an important role in fiber-related radical formation.