The crystal structure of mineral fibres. 3. Actinolite asbestos

Authors

  • Simone Pollastri <p>Department of Chemical and Geological Sciences, University of Modena and Reggio Emilia,<br />Via Campi 103, I-41125 Modena, Italy</p>
  • Lara Gigli Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14 - km 163,5 in AREA Science Park,<br />34149 Basovizza, Trieste, Italy
  • Paolo Ferretti <p style="margin-left: 0.25cm; text-indent: -0.25cm; margin-bottom: 0cm; line-height: 150%; text-align: left;" align="CENTER"><strong><span style="color: #000000;"></span></strong><span style="color: #000000;"><span style="font-family: Times New Roman,serif;"><span style="font-size: small;">MUSE - Trento museum of Sciences, Corso del Lavoro e della Scienza 3, I-38122 Trento, Italy</span></span></span></p>
  • Giovanni Battista Andreozzi Department of Earth Sciences, Sapienza University of Rome, Piazzale Aldo Moro 5, I-00185 Roma, Italy
  • Nicola Bursi Gandolfi Department of Chemical and Geological Sciences, University of Modena and Reggio Emilia,<br />Via Campi 103, I-41125 Modena, Italy
  • Kilian Pollok Institut f&uuml;r Geowissenschaften Mineralogie, Friedrich-Schiller-Universit&auml;t Jena, Carl-Zeiss-Promenade 10, D-07745 Jena, Germany
  • Alessandro Francesco Gualtieri Department of Chemical and Geological Sciences, University of Modena and Reggio Emilia,<br />Via Campi 103, I-41125 Modena, Italy

DOI:

https://doi.org/10.2451/2017PM714

Keywords:

actinolite, amphibole asbestos, Rietveld, crystal structure, iron.

Abstract

 

 The present work reports chemical and structural data of actinolite asbestos from Aurina Valley, Bolzano (Italy). The chemical composition was determined using EMPA and TG analysis, and the Fe3+/Fetot ratio was accurately evaluated with independent 57Fe Mössbauer spectroscopy. Morphology and crystallinity were also investigated through SEM and TEM investigations. Crystal structure was refined using high-resolution synchrotron XRPD data. The iron content of Aurina Valley sample is lower compared to two representative asbestiform actinolite samples (with structure refinement) taken from the literature (FeOtot 7.77 wt% against 12÷13 wt%, respectively), accounting for the reduced cell volume here measured (910.29 Å. against 912÷918 Å., respectively). Refined site scattering values of Aurina Valley sample are in agreement with those calculated from chemical compositions, and the optimized structural formula is: 

K0.02Na0.05(Na0.08Ca1.92)Ʃ=2.00(Mg3.80Fe2+0.79Fe3+0.11Al0.20Mn0.05Ni0.02Cr0.01)Ʃ= 4.98(Si7.67Al0.25)Ʃ=7.92O21.69(OH)2.31. 

The C sites M(1), M(2) and M(3) are occupied by Mg and Fe in a proportion of ~4:1, whereas the M(4) site contains mainly Ca and a very small amount of Na. Iron exclusively occupies the octahedral C sites, with Fe2+ ions occurring at the M(1,2,3) sites and the small amount of Fe3+ (13% of Fetot) ordered at the M(2) site. The refined crystal structure and cation distribution are fully consistent with results previously obtained on asbestiform and non-asbestiform samples belonging to the tremolite-actinolite-ferro– actinolite substitutional series.

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Published

2017-09-01

Issue

Vol. 86 No. 2 (2017)

Section

MINERALOGY and CRYSTALLOGRAPHY