We report on Alpine metamorphic and fluid inclusion evolution of a polyphase rodingite occurrence within the Bellecombe antigorite-serpentinite, exposed in the Piemonte zone of Aosta Valley, NW Italy. Fine-grained rodingitic rocks, derived from a protolith of basaltic dike(s), are cross-cut by a network of at least six vein generations, consisting of chlorite, diopside, and grossular garnet (Type I), andradite-grossular garnet + diopside (Type II), andradite-rich garnet + chlorite (Type III), grossular-rich garnet (Type IV), vesuvianite (Type V), and chlorite (Type VI). The fine-grained rodingite and associated veins reveal a tectono-metamorphic history similar to that of the hosting serpentinite and characterized by an earlier high pressure metamorphism, followed by decompression/re-equilibration under greenschist facies conditions and by final cooling. The fluid inclusion study, performed on primary fluid inclusions in vesuvianite from Type V veins and on secondary fluid inclusions in andradite-rich garnet from Type III veins, revealed that at P = 0.22 GPa and T = 400°C, an H 2 -bearing brine (6 wt.% CaCl 2 + 6 wt.% NaCl) with traces of was introduced into the rock. This fluid had a composition compatible with the Ca-rich H 2 -bearing, reducing aqueous solutions reported from the serpentinization front. These data point to an important event of rodingitization, probably triggered by hydration of metamorphic olivine, during the late greenschist facies Alpine evolution that was probably triggered by hydration of metamorphic olivine.

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Corundum (Al2O3) boules grown by the Verneuil process generally crack along an irregular surface parallel to the elongation axis. In order to investigate the reasons for such cracking, a half boule of blue corundum, industrially produced following the Verneuil technique, was cut into slices (about 1 mm thick) parallel or normal to the elongation axis of the sample. All the slices were analysed by optical microscopy, energy dispersive spectrometry (EDS), flame atomic absorption spectrometry (FAAS), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and by X-ray transmission topography, using synchrotron radiation. The two most interesting phenomena observed were: (a) a blue colour, the location of which was not homogeneous in the boule, but concentrated in a narrow (∼2 mm) ring in the outer region of the sample; (b) the development of a single crystal during the first stages of the growth and the formation of a macromosaic crystal, with domains that were slightly misoriented and subparallel to one another, in the middle part and at the top of the boule.

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