complexation in water solutions (Plyasunov and Grente, 1998). As follows from experimental results, silicate melts, including those similar to natural ones, also show elements of structuring (Avgustnik, 1960;Botvinkin, 1971;Vlasov et al., 1971). A model of silicate magma crystallization based on the concept of structural heterogeneity of a cooling liquid medium was proposed by Frikh-Khar (1976). Structural blocks, for instance, tetrahedral oxocentered clusters, facilitated effective metal transfer and crystallization of minerals of complex composition during recent exhalative and hydrothermal mineral and ore formation (Filatov et al., 1994).Geologists are interested in the structure of water, its transformation with temperature, and the effect of admixtures upon this transformation (Blokh, 1969;Eisenberg and Kauzmann, 1969). A series of singular temperature points, including those revealed by experiments in which one structural modification of liquid water is transformed into another modification, were reported (Ovchinnikov and Masalovich, 1977;Trincher, 1981). The terms "polymorphism" (Ovchinnikov and Masalovich, 1977) and "polyamorphism" (Yager and Wolf, 2004) are used in descriptions of this process. Elements of associativity in water are retained even under supercritical conditions at high temperatures and pressures characteristic of natural hydrothermal and metamorphic processes (Kalinichev and Gorbaty, 1998).Abstract -The effect of the real structure of solutions on crystallization is one of the basic issues of crystallogenesis, which is also important for resolving problems of genetic mineralogy. The study of the NaNO 3 -H 2 O and KNO 3 -H 2 O model systems yielded new data on anomalous characteristics of crystal-forming systems, including morphological and kinetic properties of crystals, crystal-solution equilibrium, and physical properties of solutions (light scattering, thermal properties, IR parameters, pH), providing information on the structure of solutions. The internally consistent data confirm the previously suggested variations in structural heterogeneity of solutions related to minor (2-4%) variations in their composition, which result in numerous disturbances of monotonicity (thermal-concentration oscillations) in the liquidus curves of salts. It is shown that these variations can be caused by variable size and composition of crystal hydrate clusters. The experimental data indicate that the effect of the real solution structure on crystal morphology and crystal-solution equilibrium is enhanced in multicomponent systems, including natural crystal-forming systems. Anomalous faceting and habit, zoning, a sectorial structure of crystals, and nonuniform entrapment of admixtures cannot be ruled out in these systems.
