Characterization of a soil ilmenite developed from basalt

A natural ilmenite was extracted from the silt fraction of a soil developed from basalt of Minas Gerais State, Brazil. The sample was characterized by chemical analysis, X-ray diffraction, magnetic measurements and Moessbauer spectroscopy. The Moessbauer spectrum at 293 K shows two doublets: a major subspectrum of Fe2+ (relative area 74%) and a minor one of Fe3+ (26%). An incipient magnetic structure appears at 85 K, with a broadline sextet. These results may be explained by supposing that the separate is a solid solution xFeTiO3.(1-x)Fe2O3, with x = 0.85, which is magnetically ordered at low temperature. The lattice parameters for this hexagonal structure are a = 0.5082 ± 0.0001 nm and c = 1.398 ± 0.001 nm. (orig.)