Original paper
Composition chimique et structure cristalline de la phosphuranylite Ca(UO2)[(UO2)3(OH)2(PO4)2]212H2O
Piret, Paul; Piret-Meunier, Jacqueline
European Journal of Mineralogy Volume 3 Number 1 (1991), p. 69 - 78
16 references
published: Feb 12, 1991
manuscript accepted: Jul 11, 1990
manuscript received: Feb 21, 1990
DOI: 10.1127/ejm/3/1/0069
Abstract
Abstract The crystal structure of phosphuranylite has been determined by X-ray diffraction and refined to R = 0.089 for 963 observed reflexions. The unit cell is orthorhombic, space group Bmmb (n° 63), a = 15.835(7), b = 17.324(6), c = 13.724(4)Å, V = 3.765(2)Å3, Z = 4. Chemical formula: CaO-7UO3-2P2O5 ⋅14H20 with an U/P ratio = 7/4 instead of 6/4 or 8/4 as generally presumed. The structure consists of [(UO2)3(OH)2(PO4) 2]2nn layers (type dumontite), parallel to (100), connected by Ca2+, UO2+ and H2O. The structure is compared with that of dewindtite. It is shown how two minerals whose formulae are rather different (replacement of 3Pb0 by 1CaO+1UO3+1H2O) can have similar structures, owing to subtle reorganizations
Keywords
phosphuranylite • crystal structure • new data • uranyl phosphate • dewindtite