Magnetic, chemical and x-ray studies of magnetites from Tamil Nadu, India

Natural intensity, susceptibility, and Koenigsberger ratio were determined and studies of Rayleigh loops, and high field hysteresis, and variation of susceptibility with temperature from −196° C to Curie temperature were made on a number of magnetite-quartzite and pyroxene, granulite samples from Tamil Nadu. FeO, Fe2O3, and TiO2 proportions were estimated and cell dimensions were determined. From the magnetic studies it is inferred that in general the samples contain predominantly multidomain grains. In a few cases single-domain particles are detected, while in a few other samples a mixture of superparamagnetic particles and single domain states could be inferred. The relative remanence ratio is found to increase with coercive force. The ferromagnetic mineral in magnetite-quartzites is pure magnetite with a little alteration to hematite while in pyroxene granulites it is a titaniferous magnetite with a small percentage of TiO2. It is probable that the cell dimensions are dependent on oxidation in magnetites, and on the content of TiO2 in titaniferous magnetites.