A series of alkali-borate (Na2O center dot B2O3, Na2O center dot 1.5B(2)O(3), Na2O center dot 2B(2)O(3) and Li2O center dot B2O3), and a series of alkali-molybdate (Na2O center dot 1.5MoO(3), Na2O center dot 2MoO(3) and Li2O center dot MoO3) solvents were studied with a view to find out the suitable conditions for growing single crystals from germanate phases by the flux method. The ternary systems solvent-CaO-GeO2 were investigated and crystallization temperature and crystalized phase were determined. As a main result the concentration and temperature regions of crystallization of calcium germanates (Ca5Ge3O11, CaGeO3) and of some alkali germanates (Li2GeO3, Li2CaGeO4, Na2CaGe6O14) were experimentally determined for a first time. The conditions found for Ca2GeO4 growth are significantly more favorable than those known so far. Additionally during this study, two novel unknown phases were obtained. X-ray diffractograms of the novel phases are presented. The obtained conditions are a basis for successful single crystal growth by the flux method for all mentioned germanate compounds. (C) 2015 Elsevier B.V. All rights reserved.