We have grown Mg2Si bulk crystals by the vertical Bridgman method using a high-purity Mg (6N-up) source. The grown crystals were single-phase Mg2Si and had well-developed grains (1-5 mm(3)). Lane observations and SEM-EDX observations confirmed that crystalline quality in the grains was single crystal with stoichiometric composition. Electron concentration of the single crystalline specimens grown from 6N-up-Mg was 4.0 x 10(15) cm(-3) at room temperature (RT). This value is more than one order of magnitude lower than that of specimens grown from 4N-Mg [(5-7) x 10(16) cm(-3)]. The Hall mobility of 14,500 cm(2)/Vs was observed at 45 K in the crystals grown from 6N-up-Mg. We also found that Al impurity plays an important role in the crystals grown from a low-purity Mg source. From the optical absorption measurement, we estimated that the indirect energy gap was about 0.66 eV at 300 K and about 0.74 eV at 4 K. (c) 2007 Elsevier B.V. All rights reserved.