Glasses with the compositions (60.2-2x)SiO2 center dot(16.2+x)Al2O3 center dot(16.2+x)MgO center dot 3 center dot 7TiO(2)center dot 3 center dot 7ZrO(2) (x=0, 2.3, 4.65, 6.95, 8.1 and 9.25) were annealed at temperatures in the range from 800 to 1100 degrees C. This led to the precipitation of high- or low-quartz solid solution nanocrystals, magnesium aluminosilicate, mullite and spinel, depending on temperature and chemical composition. Large SiO2-concentration (x=0) led to the crystallization of magnesium aluminosilicate as the main crystalline phase. Smaller SiO2-concentrations led to the crystallization of quartz. If these samples were annealed at temperatures <= 1000 degrees C, high-quartz solid solutions were formed which did not transfer to the low temperature modification during cooling. The microhardness of the glasses were in the range from 7 to 8.5 GPa, while the Young's moduli were 105 to 120 GPa. After annealing, the microhardness was up to 12.3 GPa and the Young's moduli up to 152 GPa. (C) 2010 Elsevier B.V. All rights reserved.