Structural and Morphological Characterization of Biogenic Magnetite Crystals

TLDR: The first conclusive evidence of biomagnetism was the discovery of magnetotactic bacteria in 1975 by Blakemore, who used magnetite to detect the earth's magnetic field as mentioned in this paper.

Abstract: The biological form of the ferrimagnetic mineral, magnetite, was discovered in molluscs (polyplacophora) by Lowenstam (1962). Marine molluscs such as chitons use a specialized tongue or radula, which is in effect a conveyor belt of mineralized teeth, to graze on the algae that adhere to intertidal rocks. Chiton teeth are capped with magnetite, the hard iron oxide retarding attrition. Magnetite has since been identified in metazoan species (Gould et al., 1978; Walcott et al., 1979) and bacteria (Frankel et al., 1979). Although the magnetic properties of magnetite had led to the suggestion that animals could use this mineral to detect the earth’s magnetic field, it was the discovery of magnetotactic bacteria in 1975 by Blakemore that provided the first conclusive evidence of biomagnetism.