Stibiotantalite from the Nanyangshan LCT pegmatite, central China: Occurrence and new data on its crystal chemistry

[Marco E. Ciriotti]

Prossima pubblicazione.

Referenza:
▪ Qu, K., Ni, P., Fan, G., Li, G., Wang, Y. (2023): Stibiotantalite from the Nanyangshan LCT Pegmatite, North Qinling Orogen, Central China: Occurrence and New Data on its Crystal Chemistry. The Canadian Journal of Mineralogy and Petrology, 61, (in press).

Abstract:
Stibiotantalite, SbTaO4, from the Nanyangshan LCT pegmatite, North Qinling Orogen, Central China is described. The mineral is associated with oxystibiomicrolite, oxycalcioroméite, hydrokenomicrolite, hydroxynatromicrolite, hydromicrolite, stibnite, bismuthinite, tantalite-(Mn), columbite-(Mn), spodumene, polylithionite, trilithionite, luanshiweiite, fluorluanshiweiite, elbaite, albite, and quartz. Results from electron microprobe data analysis (n = 4) yield the average empirical formula (based on O = 4): (Sb0.96Bi0.04)Σ1.00(Ta0.85Nb0.15)Σ1.00O4. The seven strongest X-ray powder diffraction lines are [d in Å (I)(hkl)] 3.126(100)(121), 2.964(81)(040), 5.976(27)(020), 3.515(22)(111), 1.891(22)(240), 1.736(19)(161), and 2.693(16)(131). Single-crystal X-ray diffraction (SXRD) patterns show strong reflections consistent with space group Pna21. The refined unit-cell parameters from the SXRD data are a 5.5419(2) Å, b 4.9200(2) Å, c 11.8003(5) Å, and V 321.75(2) Å3 with Z = 4. The structure has been refined to a final R1 = 0.0173 on the basis of 766 reflections with Fo > 4σ(Fo). In the previous study, the AO6 octahedron of stibiotantalite was close to an ideal octahedron. The new structure refinement of stibiotantalite from the Nanyangshan pegmatite indicates that the AO6 octahedron has a larger distortion due to the lone-pair effect of Sb3+. The high-quality structural data presented in this study gives a more accurate portrayal of the crystal structure of stibiotantalite than provided in the original description of the mineral.

[Marco E. Ciriotti]

Pubblicazione effettuata.

Referenza:
▪ Qu, K., Ni, P., Fan, G., Li, G., Wang, Y. (2023): Stibiotantalite from the Nanyangshan LCT Pegmatite, North Qinling Orogen, Central China: Occurrence and New Data on its Crystal Chemistry. The Canadian Journal of Mineralogy and Petrology, 61, 965-977.