Thermal behaviour of synthetic pyroaurite-like anionic clay with molar ratio Mg/Fe=2 was studied in the range of 60-1100C
during heating in air. TG/DTA coupled with evolved gas analysis, emanation thermal analysis (ETA), surface area measurements,
XRD, IR and Mssbauer spectroscopy were used. Microstructure changes characterized by ETA were in a good agreement with the
results of surface area measurements and other methods. After the thermal decomposition of the pyroaurite-like anionic clay,
which took place mainly up to 400C, a predominantly amorphous mixture of oxides is formed. A gradual crystallization of MgO
(periclase) and Fe2O3 (maghemite) was observed at 400-700C by XRD. The MgFe2O4 spinel and periclase were detected at 800-1100C. The spinel formation was also confirmed by Mssbauer spectroscopy.