Magnetic hyperfine parameters of iron containing minerals in coals

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Abstract
Mössbauer spectroscopy of 57Fe is used to study the hyperfine parameters of iron minerals in coals and shales. Mössbauer spectroscopy at low temperatures using a large external magnetic field permits the identification of the electronic ground state of the iron ions in the minerals. The hyperfine parameters of pyrite, iron sulfates and clay minerals are studied in order to characterize and identify the iron minerals in the coals. The full understanding of the magnetic behavior of the iron containing minerals is of importance for potential magnetic separation processes. We have also observed the presence of a Mössbauer spectrum with parameters very close to those of pyrite, but with a smaller electron density at the 57Fe nucleus. This particular spectrum was associated with coal samples rich in a pyrite type called ’’framboidal’’. This led us to the study of in situ ’’amorphous’’ pyrite. All the coal samples studied were from West Virginia seams.