New Crystal-Structure Data on Bohuslavite, Fe³⁺₄(PO₄)₃(SO₄)(OH)(H₂O)₁₀·<i>n</i>H₂O

Abstract

Bohuslavite, Fe3+4(PO4)3(SO4)(OH)(H2O)10·nH2O, was first described from the Buca della Vena mine (Apuan Alps, Tuscany, Italy) and from the Horní Město deposit (northern Moravia, Czech Republic). Its full characterization was a difficult task, owing to the very low diffraction quality of available material. Notwithstanding a physically reasonable structural model, some issues remained uncertain. A new intensity data collection on a sample from the Buca della Vena mine allowed us to improve our knowledge of the crystal structure of bohuslavite. This mineral is triclinic, P1, with unit-cell parameters a = 13.3722(15), b = 13.3488(18), c = 21.585(3) Å, α = 92.345(6), β = 90.153(8), γ = 120.34(2)°, V = 3321.2(11) Å3, Z = 4. The crystal structure of bohuslavite has been refined to R1 = 0.1498 on the basis of 19,578 unique reflections with Fo > 4σ(Fo) and 773 refined parameters. The actual (SO4) distribution is clarified, as well as the role of some H2O groups, whereas some minor details remain to be solved.

Keywords

• bohuslavite
• sulfate
• phosphate
• iron
• crystal structure
• Buca della Vena mine