Assessment of the potential hazard represented by natural raw materials containing mineral fibres—The case of the feldspar from Orani, Sardinia (Italy)

• Published in: Journal of hazardous materials 2018-05, Vol.350, p.76-87
• Main Authors: Gualtieri, Alessandro F., Gandolfi, Nicola Bursi, Pollastri, Simone, Rinaldi, Roberta, Sala, Orietta, Martinelli, Giovanni, Bacci, Tiziana, Paoli, Federica, Viani, Alberto, Vigliaturo, Ruggero
• Format: Article
• Language: English
• Subjects: EMPA; Feldspar; Rietveld; SEM; Tremolite
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2018.02.012

•A procedure to unambiguously identify the nature of the asbestos minerals in a natural feldspar raw materials was applied.•The investigated feldspar raw material from Orani (Sardinia) contains tremolite asbestos and represents a potential hazard.•Electron probe microanalysis permitted to rule out the presence of fibrous amphiboles other than tremolite.•Most of the tremolite asbestos fibres present in the raw material from Orani (Sardinia) are respirable. This work describes the nature of the potentially hazardous fibrous amphibole found in the Orani’s feldspar mine (Sardinia, Italy). To identify its nature, a protocol of analysis including morphometric, chemical and crystallographic characterizations was applied. Thanks to this approach, it was possible to classify the observed fibres as tremolite after comparing chemical data, SEM/TEM observations, FTIR/ Raman spectra and X-ray diffraction data with those reported for a standard sample. The unit cell parameters of the investigated tremolite phase are a = 9.82(1) Å, b = 18.08(3) Å, c = 5.27(1) Å, and the angle β corresponds to 104.4(1)°. The mean concentration of asbestos tremolite in the Orani’s feldspar is 0.28 wt%. Most of the fibres (0.26 wt%) are respirable ‘regulated’ fibres, representing a potential hazard. Because the total amount of tremolite in the sample is 0.6 wt%, a large fraction of it has a crystal habit other than fibrous-asbestiform or acicular. The obtained results allowed us to suggest possible solutions for a safe exploitation and mineral processing of the Orani’s mine. The procedure proposed herein may be a general tool suitable to identify the mineralogical nature of fibrous minerals in raw materials and assess if they may represent a potential health/environmental hazard.