Boron and boron compounds are widely used in industrial applications. In the boron reserves colemanite is one of the most important underground riches. In this study, the dissolution of thermally dehydrated colemanite in aqueous sulphuric acid solutions was investigated in a batch reactor employing the parameters of dehydration temperature, acid concentration and reaction temperature. It was found that the dissolution rate increased with increasing dehydration temperature, acid concentration and reaction temperature.