Experimental investigations in the system rare-metal granite–Na2O–SiO2–H2O with the addition of aqueous solutions containing Rb, Cs, Sn, W, Mo, and Zn at 600°C and 1.5 kbar showed that the typical elements of rare-metal granites (Li, Rb, Cs, Be, Nb, and Ta) are preferentially concentrated in hydrosilicate liquids coexisting with aqueous fluid. The same behavior is characteristic of Zn and Sn, the minerals of which are usually formed under hydrothermal conditions. In contrast, Mo and W are weakly extracted by hydrosilicate liquids and almost equally distributed between them and aqueous fluids. Liquids similar to those described in this paper are formed during the final stages of magmatic crystallization in granite and granitepegmatite systems. The formation of hydrosilicate liquids in late magmatic and postmagmatic processes will be an important factor controlling the redistribution of metal components between residual magmatic melts, minerals, and aqueous fluids and, consequently, the mobility of these components in fluid-saturated magmatic systems enriched in rare metals.