The crystallisation of a Li0.6Al0.1Si0.6O1.575N0.05 glass matrix has been studied by means of X-ray powder diffraction at 730degreesC. Data diffraction and EDS analysis have shown the simultaneous formation of two crystalline phases Li2SiO3 and Li0.6Al0.6Si2.4O6 (so-called virgilite) with no evidence for the presence of nitrogen in these phases. The Avrami exponent has been determined for each phase from several time-dependent X-ray diffraction studies. The values of the Avrami exponent, close to 2.25, suggest that crystallisation is tri-dimensional and controlled by a diffusion process with a decreasing nucleation rate at 730degreesC. With respect to the aluminium-containing phase, a long time heat treatment at this temperature has not revealed a phase transition from the metastable hexagonal symmetry to the stable tetragonal one. The XRD correlation length values, from the Scherrer equation, are close to 450 Angstrom. Furthermore, SEM micrographs have confirmed the volume crystallization of this glass composition and the approximate linear dimension of the regions of diffracting materials. (C) 2003 Kluwer Academic Publishers.