X-ray characterization of Mg, Fe, and Mn natural end-members of the axinite group

New powder X-ray diffraction data for magnesio-, ferro-, and manganaxinite, obtained from samples closely corresponding to the three end-members of the axinite mineral group, were obtained using a conventional Bragg-Brentano diffractometer. Space group is P (1) over bar. Powder patterns were indexed using Peacock's normal orientation, which gave: a = 7.1381(3), b = 9.1626(4), c = 8.9421(4) Angstrom, alpha = 91.903(4), beta = 98.105(3), gamma = 77.468(4)degrees for magnesioaxinite; a = 7.1479(4), b = 9.1962(5), c = 8.9576(4) Angstrom, alpha = 91.857(4), beta = 98.177(4), gamma = 77.359(4)degrees for ferroaxinite, and a = 7.1849(4), b = 9.2152(5), c = 8.9765(4) Angstrom, alpha = 91.761(4), beta = 98.153(4), gamma = 77.150(4)degrees for manganaxinite. Peacock's orientation has been adopted in all recent structural and crystal chemical studies of axinite, but it differs from that reported on the JCPDS cards (29-344, 27-076 and 27-084, respectively). New data include an increased number of indexed peaks. (C) 2000 International Centre for Diffraction Data. [S0885-7156(00)00303-1].