Crystal chemistry of a manganian ludwigite

A ludwigite specimen with unique composition, Mg-1.99(Fe3+ Mn-0.60(3+) 0.27 Al0.11Ti0.03)O-2[BO3], from the Jakobsberg Fe-Mn oxide deposit, Filipstad, Varmland, Sweden, has been investigated by means of electron-microprobe ana lysis, Mossbauer spectroscopy and X-ray diffraction techniques. The ludwigi te occurs with brucite, chondrodite and spinel in calcite marble. The ortho rhombic unit-cell parameters are a = 9.240 (3) Angstrom, b = 12.362 (4) Ang strom and c = 2.9869 (8) Angstrom. Crystal-structure refinements have been carried out in the space group Pbam to R = 5.7%. In terms of interatomic di stances it is similar to ordinary, Mn-free ludwigite, except in that there is a distortion of Jahn-Teller type in the octahedra labelled M4, where Mn3 + resides together with a major fraction of the Fe3+. A complete solid solu tion series between ludwigite and fredrikssonite, Mg2Mn3+O2[BO3], is indica ted.