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

Abstract

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¯. Powder patterns were indexed using Peacock's normal orientation, which gave:a=7.1381(3),b=9.1626(4),c=8.9421(4) Å, α=91.903(4), β=98.105(3), γ=77.468(4)° for magnesioaxinite;a=7.1479(4),b=9.1962(5),c=8.9576(4) Å, α=91.857(4), β=98.177(4), γ=77.359(4)° for ferroaxinite, anda=7.1849(4),b=9.2152(5),c=8.9765(4) Å, α=91.761(4), β=98.153(4), γ=77.150(4)° 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.