Phase formation in the complex system Nd2O3-Ta2O5-K2Mo3O10-B2O3 within the region of neodymium heptatantalate NdTa7O19 (NHT) phase stability has been studied. NHT single crystals have been obtained by spontaneous nucleation from high-temperature solutions using K2Mo3O10-B2O3 as a flux. An attempt was made to correlate morphological variation of grown crystals with fluxed melt composition. Increasing K2Mo3O10 concentration in the K2Mo3O10-B2O3 solvent results in development of crystallographic simple forms {0001}. Micromorphology of short prismatic and plate-like NHT crystals is characterized by growth pits and lines of growth layers on these pinacoidal faces. (C) 2004 Elsevier B.V. All rights reserved.