Hingganite-(Ce) and hingganite-(Y) from Tahara, Hirukawa-mura, Gifu Prefecture, Japan: The description on a new mineral species of the Ce-analogue of hingganite-(Y) with a refinement of the crystal structure of hingganite-(Y)

Abstract

Hingganite-(Ce), Ce2[]Be2Si2O8(OH)2 or CeBeSiO4(OH), occurs in a pegmatite at Hirukawa-mura, Gifu Prefecture, Japan. It is pale tan in color, vitreous and transparent, with a white streak. The Mohs hardness is 5-6, and the calculated density is 4.28 g/cm3. An electron microprobe analysis gave the empirical formula (Ce0.82La0.32Nd0.13Pr0.06Y0.03Sm0.01 Gd0.002Dy0.001Ca0.60)Σ1.97Fe0.24Be2.02Si2.02O8.20(OH)1.52. The lattice parameters were determined by the Rietveld method coupled with the imaging plate Gandolfi XRD data: SG = P21/a, a = 9.8973(11), b = 7.6282(8), c = 4.7505(6) A, β = 90.416(8)°, V = 358.64(7) A3, and Z = 2 for Ce2[]Be2Si2O8(OH)2. The three strongest lines in the powder XRD pattern [d(A), I/I0, hkl] are (3.14, 86, 211 and 211), (2.85, 100, 121 and 121) and (2.56, 46, 311, 221 and 311). Hingganite-(Ce) is a new member of the gadolinite-datolite group of minerals. It is the Ce-analogue of hingganite-(Y), and ideally, is the Fe-free analogue of gadolinite-(Ce). A single crystal of hingganite-(Y) from the same locality showed a chemical composition of (Y1.21Ca0.28Nd0.06Gd0.06Dy0.06Yb0.05Er0.04Ce0.04Sm0.03Ho0.03Lu0.02Pr0.01Tm0.01Tb0.01La0.01)Σ1.92Fe0.23Be2.07Si2.07O8.19(OH)1.55. A negative anomaly was observed for Ho in the lanthanide distribution pattern of hingganite-(Y). A single crystal structure refinement of hingganite-(Y) converged to R = 0.0329 with the lattice parameters of: a = 9.8830(16), b = 7.6091(9), c = 4.7423(9) A, β = 90.342(14)°, and V = 356.62(10) A3.