Using differential scanning calorimetry (DSC) measurements in combination with structural and optical characterization we have investigated the formation conditions of different phases of tris(8-hydroxyquinoline)aluminium (Alq(3)). We have identified the delta-phase as a high-temperature phase of Alq(3) being composed of the facial stereoisomer, and report an efficient method to obtain blue luminescent Alq(3) by a simple annealing process. This allows the preparation of large amounts of pure delta-Alq(3) by choosing appropriate annealing conditions, which is necessary for further characterization of this blue-luminescent phase, and offers the possibility of fabricating blue organic light-emitting devices (OLEDs) from this material.