Acicular black crystals of guettardite [12416-22-7] occur in small cavities at the Pitone marble quarry near Seravezza (Apuan Alps, Tuscany, Italy). The mineral is monoclinic with a 20.05(5), b 7.95(2), and c 8.44(2) Å, β 102°46' ± 10', space group P21/a. Reflectance values were detd. in air and in oil at various wavelengths. The Vickers hardness no. is 189. The proposed ideal formula is Pb(Sb,As)2S4, i.e., a ratio PbS:(Sb,As)2S3 = 1.
Guettardite from Tuscany, Italy: a second occurrence / G., Bracci; D., Dalena; P., Orlandi; G., Duchi; Vezzalini, Maria Giovanna. - In: CANADIAN MINERALOGIST. - ISSN 0008-4476. - STAMPA. - 18:(1980), pp. 13-15.
Guettardite from Tuscany, Italy: a second occurrence
VEZZALINI, Maria Giovanna
1980
Abstract
Acicular black crystals of guettardite [12416-22-7] occur in small cavities at the Pitone marble quarry near Seravezza (Apuan Alps, Tuscany, Italy). The mineral is monoclinic with a 20.05(5), b 7.95(2), and c 8.44(2) Å, β 102°46' ± 10', space group P21/a. Reflectance values were detd. in air and in oil at various wavelengths. The Vickers hardness no. is 189. The proposed ideal formula is Pb(Sb,As)2S4, i.e., a ratio PbS:(Sb,As)2S3 = 1.
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