Lodestone: Natures only permanent magnet - What it is and how it gets charged

Magnetite and Titanomagnetite exhibit magnetic properties which are attribu table to the micro-structures developed during oxidation and exsolution: Al l magnetite iron ores which are lodestones contain maghemite. These lodesto nes have He between 10 and 30 mT, SIRM between 8 and 18 Am(2)kg(1), and R-1 between 0.10 and 0.26. Magnetite, titanomagnetite and metals have REM valu es (ratio of NRM to SWM) < 0.05. Samples (called fulgarites) obtained from the Smithsonian Institution have REM values ranging from 0.45 to 0.92. The REM value serves as a witness parameter to the magnetic fields associated w ith the lightning bolt. If a high REM value (say >> 0.1) can be verified as not to be due to contamination by man and does not contain MD hematite the n the rock has LRM (lightning remanent magnetization). The magnetic field a ssociated with lightning can be revealed from an isothermal remanent acquis ition (RA) curve.