Bismutotantalite from northwestern Argentina: Description and crystal structure

• Published in: The Canadian Mineralogist
• Main Authors: Galliski, Miguel Angel, Marquez Zavalia, Maria Florencia, Cooper, Mark A., Cerný, Petr, Hawthorne, Frank C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Mineralogical Association of Canada
• Subjects: Argentina; Bismutotantalite; Crystal-Structure Refinement; Electron-Micropode Analysis; Granitic Pegmatite; La Elvirita; https://purl.org/becyt/ford/1.5; https://purl.org/becyt/ford/1; Argentino; Instituto Antártico Argentino
• Online Access: http://hdl.handle.net/11336/40364

Bismutotantalite occurs in albite-rich cores of the La Elvirita granitic pegmatites, northwestern Argentina, associated mainly with bismuth, bismuthinite, ferrotapiolite, manganotantalite, microlite, uranmicrolite, bismutomicrolite, hafnian zircon and montebrasite. A fresh, cm-sized crystal, dark grey with a greasy luster and D = 8.809 g/cm3, was examined. In reflected light, it is grey with very weak bireflectance; two phases can be distinguished. Electron-microprobe analysis gives the host bismutotantalite [Bi] as [Bi,Sb], (Bi0.68Sb0.32)(Ta0.89Nb0.11)O4, is enriched in Sb. Least-squares refinement of X-ray powder-diffraction data of [Bi] gave a 4.968(1), b 11.796(3), c 5.646(1) Å, V = 330.85(9) Å3. The crystal structures of [Bi] and [Bi,Sb] were refined to R indices of 1.9 and 2.4%, based on 387 and 377 observed (4σ) reflections, respectively, measured with MoKα X-radiation. Both phases are orthorhombic, space group Pcnn. Z = 4; [Bi] has a 4.9652(4), b 11.7831(16), c 5.6462(5) Å. V 330.32(6) Å3, and [Bi,Sb] has a 4.9471(4), b 11.7878(7), c 5.6048(3) Å, V 326.83(4) Å3. These results show that the centrosymmetric structure of bismutotantalite can accommodate up to ∼40% Sb3+ substituting for Bi3+ without changing to the Pc21n structure of stibiotantalite. Fil: Galliski, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Ministerio de Relaciones Exteriores, Comercio Internacional y Culto. Direccion Nacional del Antártico. Instituto Antártico Argentino. Instituto Antártico Argentino - Sede Cricyt (Mendoza); Argentina Fil: Marquez Zavalia, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto ...