Structural model of uramarsite

• Published in: Crystallography reports 2008-09, Vol.53 (5), p.771-774
• Main Authors: Rastsvetaeva, R. K., Sidorenko, G. A., Ivanova, A. G., Chukanov, N. V.
• Format: Article
• Language: English
• Subjects: ARSENATES; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Crystallography and Scattering Methods; MONOCRYSTALS; Physics; Physics and Astronomy; SPACE GROUPS; STRUCTURAL MODELS; Structure of Inorganic Compounds; URANIUM DEPOSITS; URANIUM MINERALS; URANYL PHOSPHATES; WATER; X-RAY DIFFRACTION
• ISSN: 1063-7745; 1562-689X
• DOI: 10.1134/S1063774508050076

The structural model of uramarsite, a new mineral of the uran-mica family from the Bota-Burum deposit (South Kazakhstan), is determined using a single-crystal X-ray diffraction analysis. The parameters of the triclinic unit cell are as follows: a = 7.173(2) Å, b = 7.167(5) Å, c = 9.30(1) Å, α = 90.13(7)°, β = 90.09(4)°, γ = 89.96(4)°, and space group P 1. The crystal chemical formula of uramarsite is: (UO 2 ) 2 [AsO 4 ][PO 4 ,AsO 4 ][NH 4 ][H 3 O] · 6H 2 O ( Z = 1). Uramarsite is the second ammonium-containing mineral of uranium and an arsenate analogue of uramphite. In the case of uramarsite, the lowering of the symmetry from tetragonal to triclinic, which is accompanied by a triclinic distortion of the tetragonal unit cell, is apparently caused by the ordering of the As and P atoms and the NH 4 , H 3 O, and H 2 O groups.