Ferrimagnetic Minerals a Class in the Brazilian System of Soil Classification.

Mass specific magnetic susceptibility (XLF) and frequency dependent magnetic susceptibility (XFD) are two magnetic attributes of ferrimagnetic minerals. These minerals are, in tropical and subtropical soils, represented by the minerals magnetite (Fe3O4) and maghemite (γ-Fe2O3). Maghemite is a ferrimagnetic mineral usually formed during pedogenesis and accumulates in the clay fraction of the soils. Magnetite is a lithogenic mineral that usually accumulates in the coarse (sand+silt) fractions of the soils. These minerals, besides the magnetic behavior, have a close positive relationship with the presence of micronutrientes available in soils. Data on more than 500 soil samples of different soils and soil fractions from Brazil show XLF varying from less than 10 to more than 20,000 x 10-8 m3 kg-1. Therefore, it is possible to use these minerals as a class on the Brazilian System of Soil Classification-SiBCS as a class in the family level. The ferrimagnetic soils would more than 5% ferrimagnetic minerals and XLF greater than 2500 x 10-8 m3 kg-1.