Crystal chemical and structural characterization of fibrous tremolite from Ala di Stura (Lanzo Valley, Italy)

The present work reports new chemical and structural data of fibrous tremolite from Ala di Stura (Lanzo Vally, Piedmont, Italy). From the toxicological point of view, this fibrous tremolite species exhibited high carcinogenicity in previous intraperitoneal injection experiments with rats. Crystal-chemical data were obtained by electron microprobe and ICP-MS analysis, Mossbauer and FT-IR spectroscopy, and parallel-beam X-ray powder diffraction. Fe(2+) occurs at the [M(1)+M(3)] and M(2) sites, and Fe(3+) is present only in M(2) site. No evidence of a split M(4) site was observed. The presence of Fe(2+)at both M(1) and M(3) sites was confirmed by FT-IR spectroscopy, whit M(1) = 0.09 apfu and M(3) = 0.05 apfu. The cell volume, 909.07(2) angstrom(3), is higher than that for the end-member (Ca/Mg= 2/5) tremolite, in accord with the presence of small amount of Fe; the sample has the following formula: (Ca(1.96)K(0.01)Na(0.01))Sigma(1.98)(Fe(0.03)(3+)Fe(0.26)(2+)Mg(4.69)MN(0.03))Sigma(5.01)(Si(7.99)(IV)Al(0.01))Sigma(8.00)O(22)(OH(1.98)F(0.02))Sigma(2.00).