THE CRYSTAL STRUCTURE OF MITRYAEVAITE, A MICROCRYSTAL USING SYNCHROTRON RADIATION

Abstract

The crystal structure of mitryaevaite, Al5(PO4)2[(P,S)O3(OH,O)]2F2(OH)2(H2O)8·6.48H2O, a secondary mineral from the alteration zone of carbonaceous, vanadium-bearing shales from northwestern Karatau Range and Zhabagly Mountains, southern Kazakhstan, has been determined from a microcrystal (8 × 10 × 65 μm) using synchrotron X-radiation. The structure was solved by direct methods and refined to R1 = 0.057 and S = 1.020 using 2111 unique observed reflections (|Fo| ≥ 4σF). The structure is triclinic, space group P1̅, a 6.918(1), b 10.127(2), c 10.296(2) Å, α 77.036(3), β 73.989(4), γ 76.272(4)°, V 663.8(2) Å3, Z = 1. The structure of mitryaevaite contains five-membered finite chains of corner-sharing (Alϕ6) octahedra. The chains are cross-linked via (PO4) tetrahedra to produce complex slabs that are parallel to the a axis, and that are in turn linked through additional (PO4) tetrahedra to form layers parallel to the (011̅) plane. The heteropolyhedral layers are linked together through hydrogen bonds to H2O groups located in the interlayer region.