Magnetic properties of pseudomorphs of siderite

Siderite pseudomorphous are formed by a natural hydrothermal transformation of ferrous carbonates into various iron oxides and hydroxides. In these compounds, small antiferromagnetic particles of αFe 2 O 3 and a FeOOH are bound by hydrated organic and inorganic (silicates, carbonates,... ) materials. N.G.R. along with magnetic studies have been performed. Mossbauer spectra show relaxation behaviour which cannot be related to superparamagnetism. Along with these studies, X rays, chemical and thermogravimetric analysis show that the sample composition is about 50% of αFe 2 O 3 , 50% of αFeOOH, 0.5% of γFeOOH. The mean size of the particles is about 250 A.