Crystal chemistry of natural occurring asbestos tremolite from calabrian ophiolites

The present work reports a detailed chemical and structural characterization of a fibrous tremolite sample from an abandoned serpentine quarry located in Mount Reventino (Calabria, Italy), by using SEM-EDS analysis, Mossbauer spectroscopy, and X-ray powder diffraction. Cell parameters, fractional coordinates and site scattering were refined using the Rietveld method. Results showed that the sample contains small amount of Fe, being the % ferro-actinolite content of ca. 3%. In particular, Fe2+ is preferentially allocated at M(1)+M(3) octahedral sites, and Fe3+ only occurs at M(2). Combining chemical, spectroscopic and structural data the following empirical formula has been derived: (A)(Na-0.124)(Sigma 0.124)(M(4))(Ca1. 922Na0.003Fe0.0262+Mg0.049)(Sigma 2.000 Sigma 1.000)][(Si3.946Mg1.960Fe0.0402+)-Si-T(1))(Sigma 2.000)(M(2))(Mg1.963Fe0.0243+Fe0.0132+)(Sigma 2.000)Mg-M(3)(0.931) Fe-0.069(2+))(Sigma 1.000)] [(T(1))(Si-4.000)] O-22(O(3))(OH2.000)(Sigma 2.000). Considering that both the presence of Fe and its coordination environment within the mineral structure are primary factors for pathological effects, the identification of Fe bearing asbestos tremolite in the investigated area may represent a potential hazard for human health.

Automated summary

This study provides a detailed chemical and structural characterization of a fibrous tremolite sample from an abandoned serpentine quarry in Calabria, Italy, revealing the presence of Fe which could pose potential health hazards. The identified Fe-bearing asbestos tremolite may have pathological effects due to its coordination environment within the mineral structure.