On the Crystal-Chemistry of Bjarebyite, BaMn2+2Al2(PO4)3(OH)3, From the Palermo #1 Pegmatite, Grafton County, New Hampshire, Usa

Bjarebyite, BaMn2+2Al2(PO4)3(OH)3, is a rare secondary phosphate mineral in granitic pegmatites. From the crystallographic point of view it is exhaustively described in the monoclinic unit cell with a 9.0671(2) Å, b 12.1500(4) Å, c 4.9403(1) Å, β 100.399(2)°, V 535.31(2) Å3, and space group P21/m. Single crystal X-ray diffraction data were collected with MoKa radiation. The hydrogen positions were located by difference Fourier map and refined in the final steps of the crystal structure anisotropic refinement, leading to an R index of 1.99%. A very good agreement was found with microprobe chemical analyses and bond valence calculations which show expected values for all the atomic sites. These features were confirmed by comparing the Raman spectra of bjarebyite and kulanite.