Аннотация:An increase in the concentration of Nd203 in the system NdAI3(BO3)4-(K2Mo3OI0-Nd203-B203) leads to the replacement of NAB by a phase with a high content of neodymium - NdBO3. Compounds with ratios of Nd/Al=1/2 and (Nd+Al)/B=3/4, i.e. metaborate crystal-chemical formula: NdAl2.07[B4010]O0.9 NdAl2.01[B4010]O0.9 are formed in fluxed melts enriched with B203. Low concentrations of B and Nd oxides in the solvent lead to the formation of Al5B09. Fluxed melts with 20% concentration of NAB are most useful for growing NAB crystals. A mono-mineralic region is formed at higher concentrations (and temperatures) . NdAl-metaborate is formed mostly at a NAB concentration less than 20% but with a higher concentration than 12 mole% of Nd203 in the solvent.