Brookite was obtained from fresh coprecipitates prepared by neutralization of TiCl₄ and CaCl₂ solutions, under hydrothermal conditions of 220–560°C and water pressure of 1 kbar. This phase developed from anatase and through the decomposition of a titanate in solutions containing Ca⁺⁺ ions, which were established as a new stabilizer for the formation of the phase. A reaction diagram, indicating the formation region of the phase, was determined.