In order to study the effect of ZrO2 and TiO2 on the nucleation mechanism in a lithium aluminosilicate glass, a composition similar to that of the commercially available ROBAX (TM) glass (Schott AG) was modified. Glasses with different concentrations of ZrO2 and TiO2 were melted and studied using differential scanning calorimetry measurement. The glasses are thermally treated for different periods of time and at various temperatures and then investigated by X-ray diffraction and electron microscopy. Both scanning electron microscopy and transmission electron microscopy were applied to study size and shape of the formed crystal phases and possibly to obtain lattice plane distances. Increasing the concentration of the nucleation agents led to the spontaneous formation of Zr1-x Ti1+x O-4 nano crystals during cooling. In any case, the nuclei contain much more titania than zirconia, possess an elongated shape, and are embedded in a shell enriched in alumina.