Single-crystal structure refinement of bukovite, (Cu3Fe)Σ4Tl2Se4

• Published in: Journal of geosciences (Prague) 2023-12, Vol.68 (3), p.179-184
• Main Authors: Sejkora, J., Mauro, D., Biagioni, C.
• Format: Article
• Language: English
• Subjects: Calcite; Copper; Crystal structure; Electron microprobe; Electron probe microanalysis; Electron probes; Empirical analysis; Gangue; Iron; Mercury; Mineralization; Minerals; Parameters; Single crystals; Software; Spectrum analysis; Tetrahedra; Unit cell; Uranium; X rays; X-ray diffraction
• ISSN: 1802-6222; 1803-1943
• DOI: 10.3190/jgeosci.373

Single-crystal X-ray diffraction study of bukovite, ideally (Cu3Fe)Σ4T12,Se4, was performed using a specimen from the Ustalec uranium deposit, 15 km west of Horažd'ovice, SW Bohemia, Czech Republic. In the studied specimens, bukovite occurs in calcite gangue with uraninite associated with bytizite, chameanite, clausthalite, hakite-(Hg) and umangite. Electron microprobe analysis gave (in wt. % - average of 20 spot analyses): Cu 19.90, T1 41.21, Fe 5.55, S 0.31, Se 31.60, total 98.57. On the basis of 10 atoms per formula unit, the empirical formula of bukovite is (Cu3.06Fe0.97)Σ4.03 T11.97(Se3.91S0.09)Σ4.00 (Z = 1). Unit-cell parameters are a = 3.9694(8), c = 13.694(3) Å, V = 215.77(10) Å3, space group I4/mmm. The crystal structure was refined by single-crystal X-ray diffraction data to R1 = 0.0264 for 92 unique reflections with F > 4σ(F0) and 10 refined parameters. The crystal structure of bukovite can be described as formed by single mackinawite-like {001} layers of edge-sharing (Cu,Fe)-centered tetrahedra, with T1 atoms hosted in eight-fold cubic coordinated sites intercalated between these tetrahedral layers. The role of Fe is discussed and the chemical formula (Cu3Fe)Σ4T12Se4 is proposed.