SOME ADDITIONAL HYSTERESIS PARAMETERS FOR A NATURAL (TITANO)MAGNETITEWITH KNOWN GRAIN-SIZE

The grain-size dependence (250 down to <5 mu m) of the hysteresis prop erties of a natural magnetite and a natural titanomagnetite were deter mined with an Alternating Gradient Magnetometer. In addition to the cl assical hysteresis parameters (M(r)/M(x), H-c, H-cr, H-cr/H-c) three a dditional hysteresis parameters; (MDF(hys), MIF(hys) and chi(hys)) wer e obtained from the loops (von Dobeneck, 1993). The classical hysteres is parameters agree well with data of Hartstra (1982), indicating that the small sample size of the ACM specimens does not hinder acquisitio n of meaningful data. The additional hysteresis parameters seem to dep end on mineralogical composition but show little grain-size dependence . chi(hys)/chi(lf) is similar to 1.6 for coarse grain-size fractions a nd decreases with grain size in fine fractions. The onset of the decre ase corresponds to the PSD-MD transition.