Abstract—This paper examines the effect of size parameters of magnesium hydroxide nanoparticles prepared by different methods on the formation of hydrosilicate nanoscrolls with the composition Mg3Si2O5(OH)4 under hydrothermal conditions, their geometric characteristics, and their thermal behavior. Magnesium hydrosilicate nanoscrolls with the chrysotile structure have been shown to form regardless of the hydrothermal treatment time and the method used to prepare magnesium hydroxide. At the same time, the nanoscroll length distribution and, especially, the nanoscroll diameter distribution depend on the method used to prepare magnesium hydroxide. In the case of hydrosilicate samples synthesized from Mg(OH)2 prepared by mixing reagents in microreactor with free impinging jets, the exothermic peak due to the conversion of magnesium hydrosilicate into magnesium silicate with the forsterite structure is located at a temperature of 817°C, whereas in the case of samples prepared from magnesium hydroxide synthesized via reverse precipitation the peak is shifted to higher temperatures (825°C).