Cation ordering in Ni-Fe olivines: corrections and discussion

Several apparent errors and one major inconsistency have been discovered in our examination of the relation-ships among the unit cell dimensions, bulk compositions and octahedral site occupancies of the Ni-Fe olivines synthesized and studied by Annersten et al. (1982). The first but probably least important ofthese discrep-ancies involves nonconformity among bulk compositions (XTf), ttre Ml and M2 site occupancies (Xff) calculated from fitted, high-temperature M<irssbauer spectra, and the areas themselves. The spectra were "corrected for difrer-ent recoil-free fractions of iron in the Ml and M2 sites," and although it is not clear to the nonspecialist how (or why) these corrections were applied, they may account for some but not all of the discrepancies reported in Table 3 of Annersten et al. For their sample Hl4, reporte