Iron ore to lodestone: With lightning assist

Abstract

A lodestone is a piece of magnetite or titanomagnetite iron ore having an extremely intense remanent magnetization; it is nature's only permanent magnet. This magnetization intensity is larger than could be acquired in any iron ore by any known natural mechanism through exposure to just the Earth's magnetic field. This is revealed by the large ratio (REM) of the measured (NRM) - natural remanence, to the (SIRM) - saturation remanence.We describe new details of the mechanism by which part of an iron ore body becomes a lodestone: Exposure to lightning bolt related electric discharge's magnetic fields is required.While the lightning bolt related magnetic fields are necessary, they are not sufficient for creation of a lodestone. We show that the iron ore must be previously magnetically “hardened” into what we term a “latent lodestone iron ore” condition before the transformation to lodestone can be achieved.A magnetic hardness continuum (characterized with magnetic hysteresis loop parameters) for a range of magnetite and titanomagnetite iron ores demonstrates how the hardening is created by alteration; in magnetite through oxidation scenarios and in titanomagnetite by solid state exsolution and oxidation.Large REM (evidence of lightning), the *Polarity signature (which we identify with iron powder patterns) reflecting the large REM, and the location on the magnetic hardness continuum (latent lodestone state resulting in largest possible magnetization), provides important details to the lodestone story.