Wakefieldite-(Y) from Montaldo di Mondovì (Italy): New data and crystal structure

Wakefieldite-(Y) with approximate composition (Y 0.40Nd 0.15Ce 0.15- Ca 0.15Th 0.15)(V 0.92As 0.08)O 4 is reported from an abandoned Fe- and Mn-ore mines located at Montaldo di Mondovì, Piedmont, Italy. The zircon-type crystal structure (space group I4 1/amd; a = 7.2591 Å , c = 6.4255 Å ) has been refined (R = 0.017 for 175 independent reflections) using X-ray diffraction data collected on a crystal from this locality. Our data confirm the validity of the species that previously had been only roughly defined using an impure pulverulent sample from Wakefield Lake (Quebec, Canada). The substantial (30%) joint replacement of Ca 2+ and Th 4+ for Y 3+ in the present wakefieldite-(Y) expands the cell volume of pure YVO 4 and could anticipate the existence of minerals with zircon-type structure and (A 0.5 2+A' 0.5 4+)T 5+O 4 composition. © Springer-Verlag 2011.