The crystallization of zeolites from dense hydrogel usually requires a long synthesis period, which results in products in the form of polycrystalline aggregates with a broad particle size distribution. In the present study, we demonstrated that the crystallization of mordenite in an organic-free dense-hydrogel system (0.275 Na2O:0.025 Al2O3:1 SiO2:25 H2O) can be triggered using an intermediate stirring method - quenching and opening the reactor during synthesis and using a spatula to stir the substances for 1 min. Moreover, the particle size and size distribution of the crystalline products were found to vary with the timing of the intermediate stirring. Our observations on the amorphous aluminosilicate particles showed that worm-like particles (WLPs) would transform into large spherical condensed aggregates (CAs) with ca. 10 μm diameter through aggregation and coalescence, which took place at the beginning of the synthesis (5 h) under static conditions. However, it was not until 110 h that we could detect the presence of crystalline products by X-ray diffraction. Based on the results, we speculated that the mordenite nuclei were formed inside WLPs, and the formation of large CAs and the increasing packing density of the solid phase further reduced the chance for these nuclei to contact with the liquid phase for the growth.