Magnetic minerals in the crust of the Earth

The magnetic, remanence-carrying minerals in the Earth's crust are principally oxides. One group, the titanomagnetites and their derivatives which are ferrimagnetic spinels, occur mainly in igneous rocks. Haematite, a non-collinear antiferromagnet, is the remanence carrier in many sedimentary rocks. The combination of the geomagnetic field and a perturbation, present only at the time of formation of the rock, results in imprintation of a record of the field which is preserved over geological time. The retrieval and assessment of the recorded information requires a knowledge of the intrinsic properties of the minerals and the influence of microstructure, which is controlled by the environment in the host rock, on the magnetic properties.