Asbestos amphiboles: effects of comminution on tremolite and actinolite regulated and unregulated fibres

Crocidolite, amosite, anthophyllite, tremolite, actinolite besides the chrysotile serpentine polymorph fall within the classcation of asbestos, whose commercial use is banned, and environmental and human exposure levels regulated. However, the cited amphibole species can crystallise in asbestiform or non-asbestiform habit and therefore their morphological characterization has a key role in assessing a reliable asbestos hazard scenario. Furthermore, when a mechanical stress is applied to rocks containing pristine prismatic or acicular amphiboles, these phases can break, originating particles with dimensions and geometrical ratios that would label them as asbestos. Therefore, a normative and scientific crucial gap arise in the classcation criteria of a particle as a real asbestiform mineral or as a cleavage fragment (i.e. non-asbestos). The mode of comminution is fundamental for the following quantitative determination of fibres. It is critical because it can affect the morphology and geometric ratios of fibres, inducing positive or negative falses. In this framework, our work was focused on the Scanning Electron Microscopy coupled with Energy Dispersive Spettroscopy (SEM-EDS) analysis of amphiboles with asbestiform and non-asbestiform habit, subject to mechanical stress for three different time intervals, in order to assess how different time lengths of comminution control geometry and morphology of the particles.