An interesting observation is reported on the dramatic effect of HNO3 on crystalline phase evolution in the 33.3 mol% Li2O-SiO2 glass-ceramic (stoichiometric composition of lithium disilicate Li2Si2O5, LS2) prepared by sol-gel processes from tetraethylorthosilicate (TEOS) and lithium ethoxide precursors. Nitric acid (65%), in molar ratio HNO3/TEOS = 0.1, was added either to the precursor sol or to 95 degrees C dried gel. The product, which is amorphous at temperatures below 450 degrees C, transforms into crystalline lithium metasilicate (Li2SiO3, LS) at around 550 degrees C (starting temperature similar to 450 degrees C), instead of forming crystalline LS2. Phase separation in the glassy phase may be responsible for the formation of lithium metasilicate. XRD, Si-29 MAS, and Li-7 static NMR were used to follow the crystallization evolution and network structures of the materials heat-treated at various temperatures.