Morphological and structural characterization of chrysotile fibers of new formation in serpentine minerals

Musto D., Paoloni G., Plescia P., Tocino M., Sottile R.

chrysotile  nanotubes  serpentine minerals 

In this study, characterization data of some serpentine minerals from the "Rocchetta of Vara" area, in "La Spezia" province are shown. These materials present particular structures, constituted by cover materials with a low degree of crystallinity and are associated with tectonic movements. Such structures are particularly interesting for the pollution problems of asbestos fibers since they often become the center of fiber serpentine mineral formation. The analyses of the surfaces subject to the tectonic activity have been performed with the X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Infrared Spectrophotometry (FTIR) and Thermogravimetry analysis. A great difference between the primary materials (serpentine-antigorite type) and the new formation materials (amorphous or low degree of cristallinity material) has been identified. Through the integration with the other techniques of analysis, the following phases, showed in genetic sequence, have been recognised: - serpentine antigorite - serpentine lizardite - an amorphous glassy phase magnesium silicate composition rich in superficial deposits of chrysotile - a crystal superficial phase with a high quantity of chrysotile Between lizardite and the following phases, a growth of iron and manganese oxides crystallization, particularly in the dendritical and massive forms is observed. Inside the amourphous phase the presence of very small geodes (dimensions:0,5-1 mm) is observed, inside which the presence of a dense felt of chrysotile crystals with dimensions between a few microns to 500 can be noticed. Outside of the geodes the presence of sphere cave of silicon has been observed, also observed under SEM, and under the spheres nanotubes appear with magnesium silicate composition and morphology attributable to chrysotile. The most interesting thing is represented by the new fibrous formation form on the surface of glide, in correspondence with the points of maximum attrition. The results point out that the serpentines of "Rocchetta of Vara" after attrition change their morphology forming a new material that has a low grade of crystallinity, in which chrysotile is crystallied with morphology and dimension which allow them to be classified among the nanofibres material, part of which grow parallel to the other forms of serpentine and in such a way that they are hardly identificable.

Source: GEOITALIA 2007 - Sesto Forum Italiano di Scienza della Terra, pp. 77–77, Rimini, 12-14 Settembre 2007

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