A new occurrence of the rare arsenate species gasparite-(Ce), ideally CeAsO4, is reported from the Kesebol Mn-Fe-Cu deposit in south-western Sweden, where it occurs as yellowish euhedral crystals up to 0.5 mm in maximum size, in association with rhodonite, andradite, Mn2+-dominant “allanite-(Ce)”, chernovite-(Y), manganoan calcite and quartz. All gasparite samples studied are phosphatian, and quantitative SEM-EDS analyses of two representative grains gave the following average compositions: Ce0.77La0.10Nd0.10Pr0.02Ca0.01Th0.007[As0.84P0.12Si0.03]O4 and Ce0.79La0.11Nd0.11Th0.010[As0.85P0.11Si0.02]O4. The Kesebol gasparite-(Ce) is distinguished from the type material by a higher Ce/REEtot ratio and a significant P content.
The crystal structure of phosphatian gasparite-(Ce) has been determined from single-crystal X-ray diffractometer data (Mo Ka radiation, CCD area detector) and refined in space group P21/n to R(F) = 2.86 % for 776 ‘observed’ reflections with Fo > 4σ(Fo) (a = 6.929(3), b = 7.129(3), c = 6.697(3) Å, β = 104.46(3)°, V = 320.3(2) Å3, Z = 4). The results confirm that gasparite-(Ce) has a monazite-type structure, and give the idealised formula (Ce, La, Nd)[(As0.71P0.29)O4].