Precise interlaboratory measurements of various physical properties of synthetic crystals of major mantle minerals will contribute to solving current controversies in solid earth geophysics. For this purpose, high quality crystals of orthoenstatite, MgSiO3, up to 5¿2¿1 mm size, were obtained by the primary crystallization of a melt in the system MgO-SiO2-lithiumvanadomolybdate. The growth was effected by slow cooling of the melt from 930¿C to 650¿C at 1.5¿ per hour. The temperature coefficient of solubility of MgSiO3 in this solvent is 0.023 (6.5wt%/280¿C). The crystals are stoichiometric, transparent, and often euhedral, elongated parallel to c without parting or cleavage. Unit-cell dimensions are a=18.212(4), b=8.818(2), c=5.177(2) ¿ with space group Pbca. Superheating of the melt before cooling induced metastable nucleation and growth of protoenstatite which readily transformed to clinoenstatite on cooling, while rapid cooling of the melt resulted in metastable forsterites, Mg2SiO4.