Different solid-state reaction models, by interpretation of the model graphs in terms of goodness of fit to real data points (R-squared), are used to evaluate the reaction mechanism and the kinetics (E, n) for the thermal decomposition of Hekimhan-Deveci siderite ore samples. Isothermal experiments at three different temperatures (T=505 degrees C, 520 degrees C, 535 degrees C) are run for t=15-150 minutes while non-isothermal experiments are conducted at single heating rate (10 degrees C/min) using thermogravimetric analysis (TGA). Three-dimensional diffusion reaction models have been noted as the solid-state reaction model representing thermal decomposition kinetics of Hekimhan-Deveci siderite. The values of activation energy (E), the optimum kinetics obtained, are E=85.53 kj/mol (Jander three-dimensional diffusion reaction model); E=85.49 kj/mol, (Ginstling-Brounshtein three-dimensional diffusion reaction model). (c) 2008 Elsevier B.V. All rights reserved.