We synthesized a single crystal of the MgO-SiO2 system, forsterite, as large as 3500 carats. The quality of a large single crystal depends on the purity of the starting reagents and the stoichiometry of the initial mixture. Here we used high-purity (99.99 wt%) granular MgO and SiO2 specimens of similar to2 mm size, as starting materials. Reagents of this grain size are easy to handle, and are suited for obtaining a large amount (above 1 kg) of a complete stoichiometric mixture. We are capable of producing large homogeneous single crystals over 50 mm diameter and 150 mm length. (C) 2004 Elsevier B.V. All rights reserved.